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The world is faced with critical challenges to reduce its dependency on fossil fuels due to anthropomorphic CO2 emissions, which are resulting in climate change. Renewable energy provides a crucial role in reducing these emissions whilst providing sustainable energy; energy conversion of biomass forms a valuable part of a renewable energy portfolio, with capability for baseload provision, and gas and electricity production. The UK government set targets to provide energy from a renewable sources; 12% of its heat, 30% electricity and 10% of its transportation fuels from renewable resources by 2020 (MacNeil et al. 2016). Gasification is a common method used for thermal decompositions of biomass which mainly produces carbon monoxide and hydrogen which can be further used to produce heat, electricity or platform chemicals. Biomass gasification presents challenges in limitation of control systems, feedstock variability and tar production which can reduce the performance, durability of the gasifier and downstream syngas utilisation. From the literature review on biomass gasification systems, the conclusion is that well-established instrumentational control systems and strategies are not developed and applied. However, large scale gasifiers use expensive systems and will benefit from reduced cost and simple platforms. Low cost, open-source and highly robust control systems are needed for biomass gasification. Moreover, an experimental investigation is required to find optimal conditions of biomass gasification for a variety of feedstocks. Up to date, no one has reported biomass gasification control using Arduino based control systems and real-time tar detection techniques by using a PMT (Photomultiplier Tube) with different control strategies. Previously, some techniques (only temperature and pressure) have been developed by Arduino control systems for biomass gasification (All-Energy Lab, California, USA) which were not robust and have a lot of limitations. The focus of this research is centred on developing instrumentation and control systems for a novel downdraft gasifier and thermochemically processing various Miscanthus feedstocks. The current work seeks to establish robust instrumentation and control systems to improve the performance of an in-house, downdraft gasifier and seeks to identify control strategies to allow operation on the minimum tar production point with an open-source protocol. The major outcome of this research is to investigate the impact of feedstock variety on gasification performance and identify preferred Miscanthus varieties to grow at scale with optimised gasification and to allow real-time monitoring and automated optimisation of the gasification process using feedback control systems with tar detection system in a gaseous phase Five genotypes of Miscanthus feedstock were provided by Terravesta, four of these were bred in 2014 at IBERS, University of Aberystwyth. These samples are different from each other in growth habits, stem density, height, maturation time and harvest moisture content. The elemental compositions results were provided by IBERS, University of Aberystwyth which shows each Miscanthus samples varied with their genetic properties. A small-scale throated downdraft gasifier (~3.4 kW) and test rig were designed and manufactured at the University of Glasgow and built to easily assess the gasification performance under different conditions e.g. feedstock variety and with different instrumentation and control strategies. The gasification test rig allowed the testing of downstream tar detection systems, downstream gas cleaning processes and control on the output quality of the producer gas. The gasifier was operated in batch mode and to improve repeatability, the throat, grate and assembly were cleaned after each experiment. The Arduino platform was used as the core of the instrumentation and control system and integrated with opensource PLX-DAQ and Telemetry for the Graphical User Interface (GUI). Different versions of an automated instrumentation and Gasifier Control Unit (GCU) Rev 1.0, 2.0 and 3.0 were developed and installed, tested and validated. These allowed measurement of gasification process parameters: temperature, humidity, tar concentration, pressure, mass flow and liquid flow (water) and controlling the airflow. The design and development of the algorithms for the automated control systems for optimised gasification performance is discussed and includes time-based, PI-based and airflow-based control strategies. Various feedstock varieties of Miscanthus genotypes MxG, OPM12, OPM52, OPM53, OPM54 were gasified under the same equivalence ratio (ER 0.30) with various control systems and their strategies. The experimental performance found that the system achieved average gasification temperature of 600°C (for 50 mins) which produced more liquid (biocrude - moisture, bio-oil, tar, other chemical components) and producer gases with an PI-based control strategy for GCU (Rev 3.0). The experimental gasification parameters studied were carbon conversion efficiency, gas yield, cold gas efficiency and gas heating values. In this research found that, the average value for carbon conversion efficiency, cold gas efficiency, heating values and gas yield were 92%, 82%, 20 MJ/m3 and 0.83 m3/kg (biomass), respectively. Overall, GCU (Rev 3.0) system was set at 3 sec delay response time and 115000 bits per seconds (bps) baud rate. This whole system worked automatically to control the inlet airflow rate (E R) of the gasifier. It is a low cost and robust instrumentation and control system which provided accurate data on a real-time basis with an opensource protocol. Also, the output data is recorded using the telemetry (Java) based data acquisition system which is beneficial to avoid the high cost software (like: MATLAB, LabVIEW and SCADA). The reported performance parameters for the hybrid Miscanthus in the present study were comparable GCUs (Rev 1.0, 2.0 and 3.0) and improvement of their limitations to various control strategies with their GCUs systems and comparable to those from conventional Miscanthus pellet gasification in downdraft gasifiers. Also, chemical analysis of the by-products, biocrude and char, are reported along with the technical specification comparison of the GCUs systems. Overall. the Gasifier Control Unit (GCU) system is low cost with an open-source protocol, allowing other developers to benefit and expand the core of this research.

Due to the growing concerns about climate change, the power generation sector is increasingly facing pressure to reduce greenhouse gas emissions whilst maintaining energy security and supply. Co-firing biomass with coal is considered an intermediate term solution that can reduce CO2 emissions from fossil fuel utilisation and maintain use of existing power plant infrastructure. For power generators, ash deposition is still a major cause of reduced boiler efficiency and unscheduled shutdowns on heat transfer surfaces, and historically, less attention has focused on deposition due to biomass co-firing. In this research, a series of experiments were conducted on a suite of internationally traded coals, biomasses and industrial boiler fly ashes to characterise the particles formed during devolatilisation and char combustion at various residence times using a drop tube furnace (DTF) and mineral liberation analyser (MLA). The mineral transformations, associations and particle parameters determined aid the development of ash formation and erosion models. A unique mineral database using commercial coals, industrial fly ashes and biomasses was developed. This MLA database was used to assess particle parameters which influence erosion potential and determine the ash-deposition related mixed aluminosilicate species which contribute to ash deposit formation. Thermogravimetric analysis of DTF coal chars doped with biomass ashes was performed to investigate the effect of biomass-derived mineral species on the ignition temperature at varying co-firing ratios. DTF studies suggested that inherent minerals present in the biomass ash enhance the formation of sintered/deposit particles compared to firing only the DTF coal char, and that the deposit particle size increases with residence time in the DTF. Mineral composition data and the development of ternary phase diagrams showed that the DTF coal char has the added benefit of capturing metal fluxing elements such as K and Ca originally present in the biomass ash. MLA can serve as a useful tool to reveal the characteristics or mechanisms of mineral transformations, ash formation and deposition during biomass co-firing.

Despite looming energy crises, fossil resources are still widely used for energy and chemical production. Growing awareness of the environmental impact from fossil fuels has made sustainability one of the main focuses in research and development. Towards that end, biomass is identified as a promising renewable source of carbon that can potentially replace fossil resources in energy and chemical productions. Although many researches on converting biomass to value-added product have been done, biomass is still considered underutilised in the industry. This is mainly due to challenges in the logistic and processing network of biomass. An integrated biomass supply chain synthesis and optimisation are therefore important. Thus, the ultimate goal of this thesis is to develop a novel approach for an integrated biomass supply chain. Firstly, a multiple biomass corridor (MBC) concept is presented to integrate various biomass and processing technologies into existing biomass supply chain system in urban and developed regions. Based on this approach, a framework is developed for the synthesis of a more diversified and economical biomass supply chain system. The work is then extended to consider the centralisation and decentralisation of supply chain structure. In this manner, P-graph-aided decomposition approach (PADA) is proposed, whereby it divides the complex supply chain problem into two smaller sub-problems – the processing network is solved via mixed-integer linear programming (MILP) model, whereas the binaries-intensive logistic network configuration is determined through P-graph framework. As existing works often focus on supply chain synthesis in urban regions with well-developed infrastructure, resources integrated network (RIN) – a novel approach for the synthesis of integrated biomass supply chain in rural and remote regions is introduced to enhance rural economies. This approach incorporates multiple resources (i.e. bioresources, food commodities, rural communities’ daily needs) into the value chain and utilises inland water system as the mode of transport, making the system more economically feasible. It extends the MBC approach for technology selection and adopts vehicle routing problem (VRP) for inland water supply and delivery network. To evaluate the performance of the proposed integrated biomass supply chain system, a FANP-based (fuzzy analytical network process) sustainability assessment tool is established. A framework is proposed to derive sustainability index (SI) from pairwise comparison done by supply chain stakeholders to assess the sustainability of a system. Fuzzy limits are introduced to reduce uncertainties in human judgment while conducting the pairwise comparison. To design a sustainable integrated biomass supply chain, a FANP-aided, a novel multiple objectives optimisation framework is proposed. This approach transforms multiple objective functions into single objective function by prioritising each of the objective through the FANP framework. The multiple objectives are then normalised via max-min aggregation to ensure the trade-off between objectives is performed on the same scale. At the end of this thesis, viable future works of the whole programme is presented for consideration.

The slagging and fouling characteristics of biomass fuels can act as a barrier to their use as a fuel for thermal power generation. Biomasses with high alkali metal and alkaline earth metal contents, in particular those with high potassium contents, have high slagging and fouling propensities due to the formation of low melting temperature mineral phases. Under slow heating conditions using a muffle furnace, olive cake ashes have been produced at low temperature to retain inorganic volatile compounds while fully oxidizing carbon. These ashes have subsequently been heated with and without kaolin additives in different ratios to high temperatures, under both slow and fast heating rate conditions, in a muffle furnace and drop tube furnace respectively. Particular focus has been on the interactions of olive cake and kaolin in drop tube furnace combustion at temperatures ranging between 1000-1450°C and in 10% O2 – conditions representative of pulverized fuel combustion. Two additive ratio test series were conducted involving additive ratios ranging from 20% kaolin in olive cake ash (equivalent to 2% additive in raw fuel) to 50% kaolin in olive cake ash (equivalent to 10% additive in raw fuel). These tests were conducted at two temperatures: 1150°C and 1300°C. It was found that as the additive ratio increased, a threshold level for retention of volatile potassium was approached for each temperature. At 1150°C this value was 100% while at 1300°C this threshold level was approximately 80%. Furthermore, log curves were produced from the results obtained. These approximations serve to offer an insight into the levels of retention that might be achieved as a function of additive ratio. Notably, it would appear that high levels of retention are attainable with small additive ratios at the optimum temperature of 1150°C. From these additive ratio experiments it can clearly be seen that the combustion temperature has a significant effect on the efficacy of the kaolin additive. To further investigate this, an experimental test series was conducted involving DTF testing with 50% kaolin in olive cake ash at 1000°C and 1450°C. It was found that the level of retention at 1000°C was similar to that found at 1300°C (approximately 70%) while at 1450°C, 40% retention was measured. It is expected that at 1000°C the reaction is not under thermodynamic control and so the reduced retention is due to the slower kinetics at that temperature. This is not the case at the two higher temperatures of 1300°C and 1450°C. At these very high temperatures it is possible that there may be some degradation of the kaolinite additive which reduces its ability to react with the potassium. Following the experiments with olive cake and kaolin, some further tests were conducted with miscanthus and wood as alternative feedstocks with different levels of potassium. While these tests were limited in number, they did show significant signs of substantial retention of volatile potassium. With wood in particular being a favoured feedstock in large scale biomass combustion (in part due it its low ash content) further research in this area is expected. Additionally, the use of an alternative aluminosilicate additive was explored. The additive chosen was coal fly ash due to its high availability and low cost. When compared with the results achieved with kaolin, the coal fly ash that was used performed poorly. The notable contrast between the fly ash and the kaolin additive was a much lower alumina to silica ratio. When considering the ternery mineral phase diagram for the system K-Al-Si and the area of high melting temperature phases that exist where higher ratios of alumina are present, it is expected that the alumina to silica ratio of the additive is key to its performance. To further investigate this, further coal fly ash additives comprising of higher alumina to silica ratios should be tested. The use of Mineral Liberation Analysis in this research afforded the opportunity to examine the form of potassium species (by association) present in olive cake ash samples. By using this method, it was observed that the volatile potassium present in the starting fuel existed primarily as KOH. By comparing this starting material with the ash following combustion with and without kaolin at 1150°C and 1300°C, it was possible to see the transformations that occur to the potassium species. In the absence of the additive it was found that while all KOH was volatilised and lost, some of this volatile potassium migrated to form potassium silicates. In the presence of the additive however, this migration did not occur. In preference, a large proportion (up to 100%) of the KOH reacted with the aluminosilicate additive to form potassium aluminium silicate mineral phases. Thermodynamic data available in literature demonstrates that this is due to the favourable ΔG energies of formation for this reaction. By further analysis of the molar ratios of elements present in the mineral phases detected, it was possible to speculate as to the identity of potential specific compounds in the ash samples. These include the most commonly reported products of the reaction of K with Al-Si: kalsilite and leucite. By using this method it was found that the reaction product kalsilite was most likely to exist in large quantities in the samples.

The heightening world issues arises from climate change and energy security has created a strong resonance for sustainable development. The utilisation of biomass resources is amongst one of the best strategies to counter carbon emission and energy security issues for waste-to-wealth. Over the last decade, the Malaysian government has shown its clear intent to be a front-runner in the green economy through its various green economy policies and programs, particularly focus on oil palm biomass industry. However, it is observed that the diffusion rate of the industry remains relatively slow as compared to other developing countries such as Thailand and Philippine. Literature, anecdotal evidence, and advocates as well as businesses have identified that one of the non-technical factors that contribute to this problem is financing difficulties. The complication of biomass value chain creation often engaged with high risk profile, capital intensive and long payback period which is unfavourable for financing based on conventional risk assessment. Thus, this research focusses on developing a full range risk assessment model in aiding the industry stakeholder to comprehend the risk profile in managing and mitigating risk in biomass value chain in Malaysia. Multiple decision analytical tools have been employed and developed to integrate non-quantitative factors in risk assessment and design risk mitigation strategy based on the strengths and preferences of different stakeholders' role. The outputs can serve as policy recommendation to aid the authorities and policy makers to undertake policy reviews to effectively spur the biomass industry for green growth. Furthermore, financier and investor are recommended to utilise the information to enhance its financing decision, to offer financial products that customised the need of sustainable projects without losing great business opportunity. Last but not least, the framework also offers industry stakeholders a practical decision analysis and making tool to integrate preferences as well as quantitative information to mitigate risks before any losses in venturing into the biomass industry occurred.

In response to the concerns regarding environmental pollution and energy security, renewable energy has been perceived as a solution. As liquid fuel is the most consumed form of energy in the world, much attention has been paid to pyrolysis for the production of bio-oil. Bio-oil may be derived from biomass and is a potential fuel supplement and source of chemicals. However, lignocellulosic biomass-derived bio-oil is generally highly acidic and highly oxygenated than crude oil. Consequently, the bio-oil is unstable and has a comparatively low energy density. Hence, bio-oil has to be upgraded in order to use directly as fuel and other applications. One of the upgrading methods is catalytic pyrolysis using non-acidic oxides. The current project investigated the effects of calcium oxide (CaO), magnesium oxide (MgO), and zinc oxide (ZnO) on the upgrading of palm empty fruit bunch fibre (EFBF)-derived bio-oil. Apart from that, cellulose was used as feed to study the effects of the oxides on lignocellulosic biomass at its simplest form upon intermediate pyrolysis. The possible reaction pathways involved upon the utilization of the oxides were also summarized. Thermogravimetric studies revealed that the addition of MgO and ZnO did not affect the degradation behaviour of both cellulose and EFBF. However, because CaO is prone to adsorb moisture and carbon dioxide (CO2), an additional weight loss stage was observed. Even though the oxides did not affect the activation energy and mechanism of EFBF devolatilization, the amount of volatiles released reduced due to the restriction posed by the oxides. Despite the catalytic effects posed by the oxides, the reaction of the oxides with CO2 and water categorizes CaO, MgO, and ZnO as catalytic additives, rather than catalysts. Based on the results obtained when cellulose was used as feed, the reaction pathways involved in the catalytic upgrading of bio-oil were compiled. Nevertheless, upon comparing the results of the results with literature, it was concluded that the results may be used as a reference of the reactions involved during catalytic pyrolysis of biomass but it may not exactly reflect the absolute effects of the oxides on the physical properties of all bio-oils. All three oxides showed evidence in enhancing the physical properties of cellulose and EFBF-derived bio-oil, in terms of reducing the amounts of acids and oxygenated compounds. However, the oxides reacted with carbon dioxide (CO2) and water. Hence, the oxides may be considered as catalytic additives rather than as catalysts. Among the three oxides, CaO exhibited the best performance in the matter of reducing the acidity for both cellulose and EFBF-derived bio-oils, without affecting the bio-oil yield substantially. CaO also showed potential in stabilizing the EFBF-derived bio-oil without influencing the surface structure of the bio-oil.

Biomass has the potential to be a useful low-carbon replacement for coal in a number of applications. Hydrothermal carbonisation (HTC) is a pre-treatment technology which has the potential to alleviate many of the drawbacks of replacing coal with biomass, as it improves many of the fuel properties of biomass. This study was conceived as a means to investigate the impact of HTC on the suitability of biomass for this purpose, and to investigate the chemisty of HTC so that the process could be more deeply understood. HTC experiments were performed using a Parr reactor heated by a sand bath, and numerous analytical techniques were used to investigate the composition and properties of the biocoal produced. Major analytical techniques used include thermogravimetric analysis, elemental analysis, gas chromatography, XRF spectrometry, textural analsyis, and NMR. Devolatilisation of samples in a drop tube furnace was also used so that chars generated under high heating rates equivalent to what is seen in pulverised fuel combustion could be investigated. The impact of HTC process parameters on the yield and composition of biocoal was investigated, and HTC temperuature was found to have the largest impact. Increasing temperature decreased the yield of HTC, and resulted in a biocoal with a lower moisture and volatile matter content, with a higher fixed carbon content. Temperature also had a significant effect on the energy yield and energy densification of biocoal, with increasing temperature decreasing the yield and increasing the densification. A good compromise was found at a midpoint temperature of 225ᵒC, before the energy yield dropped considerably. Anaerobic digestion was calculated to have significant potenital for increasing the energy yield of HTC, especially when there is sinigicant loss of organic matter to the process liquor. The feedstock was also found to have a significant effect on the outcomes of HTC, primarily linked to the biochemical compostion of the feedstock. The removal of alkali and alkaline earth metals was found to have a strong impact on the char reactivity of biocoal, with surface area and biocoal composition providing secondary impact. Biocoal produced from soft wood biomass was shown to have a char reactivity similar to that of high-volatile bituminous coal, but HTC of biomass with higher levels of alkali and alkaline earth metals resued in a biocoal with a reactivity lower than that of the feedstock biomass, but higher than that of high-volatile bituminous coal. A coal-equvalent fuel was generated by torrefaction of soft wood biocoal. The role of water in the aromatisation reactions occuring during HTC in comparison to torrefaction was investigated. Lower levels of aromatisation were seen in HTC than in torrefaction, indicating that the water present in HTC suppresses aromatisation. HTC was found to have little impact on the yield of activated carbon production, and was found to lower the surface area of activated carbon due to deposition of organic matter in the pores of the feedstock.

The production of bio-fuel from autotrophic micro-algae are being extensively studied and documented. However very few focuses specifically on the production of bio-jet fuel, with even fewer that assesses both the environmental and economic state of micro-algal bio-jet fuel production through modelling efforts. In this research study, an integrated energy, techno-economic and life-cycle assessment deterministic model was successfully developed for the production of micro-algal bio-jet fuel. The developed model acts as a simple tool which can be used to assess the economic and environmental (Net energy ratio, greenhouse emission and water footprint) state of micro-algal bio-jet fuel production in Malaysia as well as for the identification of the key input parameters which influence these state. Prior to model construction, an initial economic investigation was carried out and compared some of the technologies/methods required for bio-jet fuel production. A base case process pathway was established based on this investigation, and formed the foundation of the process model. The integrated model simulates the major steps involved in bio-jet fuel production, which are; micro-algal cultivation, harvesting and dewatering, cell disruption and lipid extraction, lipid purification and upgrading to bio-jet fuel and an additional anaerobic digestion of residual biomass. Through the mass and energy balances and relevant equations, the material and net energy ratio (NER) are estimated with the aid of performance equations, Aspen plus, Matlab and reported data in literature. The economics of bio-jet fuel production process is evaluated by estimation of the capital and operating cost and discounted cash flow. Additionally, greenhouse (GHG) emissions and water resource consumption associated with the production of bio-jet fuel are assessed. Process model results indicates the minimum fuel-selling price (MFSP) of algal derived jet fuel would be $5.89/L, which is 14 times more than the market price of fossil derived jet fuel at $0.43/L. The NER of bio-jet fuel production was however positive, >1, more energy produced than used in the production process and CO2 is abated at a rate of -7.49tonnesCO2/L of bio-jet fuel produced. Results indicated that an additional membrane filtration process prior to centrifugation greatly reduces harvesting and dewatering energy consumption by 93%. Water usage is also estimated at 2702 tonnes/L of bio-jet fuel produced. Sensitivity analysis results indicated that lipid recovery efficiency is one of the most influential parameter and significantly influences the NER, GHG, MFSP and water usage for micro-algal bio-jet fuel production. Case scenario studies in addition to the sensitivity analysis showed algal lipid content and algal productivity significantly influences the MFSP. It was concluded that algal bio-jet fuel production plant would benefit from co-location with wastewater treatment plant and flue-gas producing sites in Kota Kinabalu, Malaysia. This includes exploitation of micro-algal species with high lipid fraction and productivity and cost effective technologies and combinations. The lowest possible MFSP achievable was $1.31/L based on an optimistic case scenario encompassing all the benefits aforementioned but still not sufficient in achieving an economically viable production process.

Solid Oxide Fuel cell (SOFC) is a promising solution to energy independence, greener energy, with high electrical efficiency and theoretically compatible to operate with gaseous carbonaceous fuel. The problem arises when the benchmark materials (Ni/YSZ) performance drop with operation with carbon fuels. Hence, this thesis aims to develop SOFC cell with alternative materials that have high electrochemical performance with dry carbon fuels for intermediate temperature SOFC. This thesis demonstrates the successful manufacturing of the anode supported cells of Ni/YSZ, Ni/ScCeSZ and Sn-Ni/ScCeSZ via reverse aqueous tape casting method. With this method, SOFC half cells with dense thin electrolyte and porous thick anode produced using multi-layered tape casting and single co-sintering stage. Ni/ScCeSZ was chosen as the base anode substrate material due to the 10ScCeSZ’s high conductivity property and better ability to tolerate carbon-based fuels. Despite the long history of Ni/ScCeSZ cell, this thesis shows the first work that compare Ni/YSZ and Ni/ScCeSZ cells for IT-SOFC with hydrogen and dry carbon fuels. Tin (Sn) introduced as dopant in the final stage to further enhanced the performance in dry carbon operation. for Sn-Ni/ScCeSZ cell. To author’s knowledge, this thesis reported the first work on the electrochemical performance in dry biogas. Comparative study of the electrochemical performance in hydrogen and dry biogas reveals that the maximum power density of Ni/YSZ cell instantly dropped by an average of 80.6% when switched from hydrogen to biogas, 0.37 W/cm² to 0.05W/cm², respectively. Ni/ScCeSZ showed better performance in both fuels, with maximum power densities of 0.42 W/cm² in hydrogen and 0.28 W/cm² biogas (37.5 % drop). Ni/YSZ and Ni/ScCeSZ show significant differences in the ASR value in biogas operation with values of 2.52 Ω.cm² and 0.72 Ω.cm² respectively. With Sn-Ni/ScCeSZ, the OCV increased with the fuel swap from 0.99 V to 1.04 V and the performance in biogas lowered only by an average of 8.3% with a maximum power density of 0.314 W/cm² in biogas. Contradict to the literature, this thesis provides a new insight to the cause of performances drop with the fuel switch which was mainly affected by the reforming ability of Ni/ScCeSZ and Ni/YSZ anode. Small amount of amorphous carbon deposited on the Ni/YSZ anode while higher amount of graphitic carbon found on the Ni/ScCeSZ and Sn-NiScCeSZ anodes. Sn increased the catalytic activity reforming and methane cracking accompanied by increase amount of graphitic carbon on the anode.

Three biochars (BC) were produced from Vietnamese biomass (acacia wood chip, rice husk, and bamboo) using Top Lid Up-draft Drum (TLUD) technology. The resulting biochars were characterized using a suite of state-of-the-art methods to understand their surface area, morphology, cation exchange capacity, and surface chemistry as a basis for determining their utility for application in agriculture in Vietnam. Adsorption experiments for ammonium (\(NH_4^+-N\)) and heavy metal (\(Zn^{2+}\)) in artificial aqueous solutions were conducted to assess the adsorption capacity of the various biochars. The mechanism of adsorption was assessed via the isotherm models (Langmuir, Freundlich, Temkin), the kinetic models (Lagergren-first order and pseudo-second order models) and the intraparticle diffusion model. Then, a real wastewater (landfill leachate) with various pollutants was used to test the adsorption capacity of the biochar under environmental conditions. Biochar surface areas (measured by BET) decreased in the order wood BC (479.34 \(m^2/g\)) > bamboo BC (434.53 \(m^2/g\)) > rice husk BC (3.29 \(m^2/g\)). Meanwhile, cation exchange capacity (CEC) followed the opposite trend, being rice husk BC (26.70 Cmol/kg) > bamboo BC (20.7 Cmol/kg) > wood BC (13.53 Cmol/kg) indicating a correlation between surface are and absorption capactiy. The morphology, as shown in SEM images corresponds with the area, showing a rough surface with pores for wood BC, a hollow honeycomb-like structure for bamboo BC, and smooth surface for rice husk BC. All three biochars produced were alkaline, with pH values around 10. The surface chemistry, measured by FTIR, indicated that carboxyl and hydroxyl groups or \(CO_3^{2+}\) group were observed for all three biochars, but \(PO_4^{3-}\) and \(SiO_2\) groups were only present in rice husk and wood BCs. The surface function groups played an important role for the adsorption of the biochars. The differences in physicochemical properties resulted to various adsorption capacities among the biochars. For example, the adsorption capacity for \(NH_4^+-N\)was in the order rice husk BC > bamboo BC > wood BC, and the adsorption process was governed by surface functional groups, cation exchange, and intraparticle diffusion. In comparison, the adsorption for \(Zn^{2+}\) was in the order bamboo BC > rice husk BC ≥ wood BC, and the the organic groups (carboxyl and hydroxyl groups), and inorganic groups (\(CO_3^{2+}\), \(PO_4^{2-}\)) mainly controlled the adsorption (rather than ion exchange). There was a strong increase in adsorption for \(NH_4^+-N\)with increasing adsorbate concentrations (20-320 mg/L), while the \(Zn^{2+}\) adsorption was slowly enhanced at adsorbate concentrations higher than 60 mg/L. However, the adsorption of both the adsorbates onto the three biochar occurred via the mechanism described as multilayer formation on a heterogeneous surface. The findings of the experiments for the wastewater (landfill leachate with concentration of \(NH_4^+-N\) up to 1790.18 mg/L) indicated that the single biochars had an excellent adsorption for \(NH_4^+-N\) with an order as for rice husk BC (44.06 ± 1.55 mg/g) > bamboo BC (40.41 ± 0.95 mg/g) ̴ wood BC (38.90 ± 1.78 mg/g). Interestingly, the binary and ternary biochars also showed a good adsorption for \(NH_4^+-N\), but not significant difference (p > 0.05) among them with the adsorption fluctuating between 39.89 and 43.10 mg/g. In addition, the ternary biochar (1:1:1) used for column test showed to be effective for \(NH_4^+-N\) removal with 43.69 ± 2.15 % removed after the leachate gone through the filter four times with flow rate 1 mL/min. However, the adsorption capacity of the single biochars was still lower than the theoretical maximum adsorption for \(NH_4^+-N\) due to the adsorption competitions of other cations (\(Ca^{2+}\), \(Mg^+\), \(Na^+\)) in the leachate. In particular, all the biochars (including binary and ternary biochars) did not adsorb \(K^+\) ions in the leachate, while \(K^+\) ions from the biochar surface were observed to exchange into the exited solvent to participate in the cation exchange process for the adsorption. Hence, the three biochars demonstrated to have good adsorption for \(NH_4^+-N\) (especially rice husk BC), while bamboo BC was identified as the best choice for \(Zn^{2+}\) removal. The information presented in this thesis will be shared with local farmers in Vietnam to help them select the most efficient biochar to use for their specific needs in water purification and/or soil fertilization utilizing existing local biomass and local production methods.

Petroleum is non-renewable and contributes to environmental pollution, thus bio-oil can be substituted as a potential alternative. However, bio-oil in its crude form cannot be used directly as fuel since it contains a high proportion of oxygenated, acidic and reactive compounds such as carboxylic acids. These are known to cause corrosion of vessels and pipework, instability and phase separation. The oxygen content of bio-oil can be reduced through hydrodeoxygenation of oxygenated compounds. In this study, the hydrogenation of short chain (C2-C4) carboxylic acids typical of model compounds present in bio-oil was investigated using commercial Pt supported on Al2O3, SiO2, carbon and graphite, and prepared Pt and Pt-Re on TiO2 catalysts. This study reports the preparation of 4% Pt/TiO2 and 4% Pt-4%Re/TiO2 catalysts for alcohol production, which were screened against their commercial counterparts, the reaction space explored in the following ranges temperature 80-200 °C, pressure 10-40 bar, time 1-4 h, catalyst 0.1-0.4 g and stirring speed 400-1000 min-1 using 4%Pt/TiO2, and kinetic modelling of acetic acid hydrogenation. The catalysts were characterized using Brunauer–Emmett–Teller (BET), X-ray diffraction (XRD), Scanning electron microscopy (SEM), H2-Temperature Programmed Reduction (H2-TPR) and NH3-Temperature Programmed Desorption (NH3-TPD) techniques. BET analysis showed features of Type IV isotherm with Type 3 hysteresis for 4% Pt/TiO2, 4% Pt-4%Re/TiO2, 4% Pt/SiO2 and 5% Pt/graphite; in contrast, 5% Pt/C and 5% Pt/Al2O3 exhibited Type 2 hysteresis. Further, both commercial and synthesized catalysts are mesoporous. The XRD peaks present in 4% Pt/TiO2 and 4% Pt-4%Re/TiO2 were found to be rutile and anatase phases of TiO2 only. The incorporation of Pt and Re into TiO2 occupied more rutile than anatase phases. Catalyst morphology of spent 4% Pt/TiO2 and 4% Pt-4%Re/TiO2 showed the formation of compact mass and agglomerates after three reuse cycles. NH3-TPD analysis showed that 4%Pt/TiO2 had the highest acidity (0.48 mmol g-1) which favoured esterification reaction. Catalyst screening showed that 4% Pt/TiO2 and 4% Pt-4%Re/TiO2 outperformed the commercial catalysts, and favoured the production of ethyl acetate and ethanol respectively. Consequently, the production of alcohol over 4% Pt-4%Re/TiO2 increased with increasing Re loading from 1 to 4%. The achieved optimum conditions were 200 °C, 40 bar, 4 h, 0.4 g and 1000 min-1 for acetic acid conversion, and 160 c, 40 bar, 4 h, 0.4 g and 1000 min-1 for ethanol production. The hydrogenation of C2-C4 acids over 4% Pt/TiO2 and 4% Pt-4%Re/TiO2 as single acid feed showed that an increase in the molecular weight of the carboxylic acid from acetic to butanoic acid enhanced the selectivity towards the respective alcohol which can be summarized: butanol > propanol > ethanol. Conversely, ester selectivity is as follows: ethyl acetate > propyl propionate > butyl butyrate. The selectivity to alcohol decreased as the reaction temperature increases from 145 to 200 °C. Higher alcohol selectivities were achieved over 4% Pt-4%Re/TiO2 in all cases. The investigation of acids in a mixed acid feed system over 4% Pt/TiO2 showed that higher alcohol selectivity was attained compared to the single feed system. On the other hand, the conversion of propanoic and butanoic acids in the mixture containing acetic acid dropped from 94 to 77% and 88.2 to 70% respectively. The presence of acetic acid in the mixed feed inhibited the other acids due to competitive effect but favoured higher alcohol selectivity. Reaction kinetics of acetic acid hydrogenation was investigated using catalyst particle sizes < 65 μm and a stirring speed of 1000 min-1 at which negligible internal and external mass transfer resistances were experienced. The reaction order with respect to acetic acid and hydrogen were found to be 0.78 and 0.35 respectively, which indicated fractional order kinetics. Hence, the experimental data was fitted with a Langmuir-Hinshelwood model for dissociative H2 adsorption. The activation energy and pre-exponential factor were found to be 80.6 kJ mol-1 and 4.6 ×10-7 kmol.kgcat-1.min-1 respectively. Finally, 4% Pt/TiO2 catalyst favours the production of esters and alcohols from the hydrogenation of short chain carboxylic acids (C2-C4) in single and multiple feed systems. However, the addition of Re to form bimetallic catalyst (4% Pt-4%Re/TiO2) further increased the selectivity towards alcohols while maintaining a high acid conversion. Furthermore, the reaction kinetics of acetic acid using 4% Pt/TiO2 catalyst was adequately described using a model that assumes a dissociative adsorption of hydrogen.

Energy security, affordability and availability, as well as ensuring environmental sustainability are crucial considerations necessary for determining the future energy mix. The forecasted continuous use of coal in power generation and chemical industries makes it an important, yet polluting energy source. This has motivated researchers into investigating various clean coal processes such as the increased interest in co-blending of coal with alternative fuels like biomass due to its carbon lean nature. However, the utilisation of coal and biomass blends in conventional thermal reactors has high potential of operational challenges associated with the differences in the physical and chemical characteristics of coal in comparison to biomass. Moreover, the differences in these fuels’ properties have been studied and concluded to lead to synergy in fuel blends reactions. Synergy in fuel blends are interactions between the biomass and coal samples that results in non-additive improvement in the experimental outcome of the thermal reaction in comparison to the additive expectation from both contributing fuels. In order to improve the uptake of such fuel blends in power plants, a clear knowledge and understanding of the fuel blends thermal behaviour is essential. There is, therefore, a need to develop suitable and efficient characterisation technique for coal and biomass blends so that their combustion performance such as optimal operating temperatures and burnout temperatures can be predicted more effectively especially relating to the cause and degree of synergy observed in such fuel blends. In this work, a series of experiments were conducted for the thermal characterisation of two coal samples (Guizhou and Yunnan coal) and three biomass samples (oat straw, rice husk and spruce wood) and their fuel blends during combustion reaction. The thermal analysis was carried out using a thermogravimetric analyser. The influence of biomass organic and inorganic constituents on coal samples during the co-blending reaction, especially the synergy influence on the char oxidation reaction has been investigated. This was to study the catalytic and non-catalytic mode of synergy. This was done by blending of coal samples with biomass ash, demineralised biomass, simulated biomass and potassium impregnated biomass samples. In addition, the quantification of the degree of synergy interaction observed was done by formulating a synergy index. Finally, the effect of such interactions in coal and biomass blends gasification was also investigated. The observations in the results included substantial decrease in the peak temperature, burnout temperature and activation energy of the char oxidation stage of most of the fuel blends. This is representative of the non-additive interaction between the coal and biomass samples and was detected in both catalytic and non-catalytic mode of synergy in varying extent. The catalytic mode of synergy are all improvements associated with the inorganic content of biomass, mostly the alkali and alkaline earth metals while the non-catalytic synergy is resulting from the organic content of biomass. During the non-catalytic mode of synergy, the deviation in the char reaction zone and its characteristic temperatures remained similar for all blend ratios, and does not vary significantly with increase in biomass blending ratio. However, the influence of hydrogen donation from the biomass volatiles increases the reactivity significantly especially relating to reaction time and burnout. In contrast, the disparity in the peak and burnout temperature associated with catalytic synergy increased rapidly with biomass blend ratio, indicating a multiplying influence of the catalysing alkali and alkali earth metals (AAEMs). Additionally, the extent of synergistic deviation was also dependent on coal’s constituents such that Guizhou coal revealed the least degree of both synergy modes. This is associated with its with high hydrogen – to –carbon ratio which minimise the interactive influence from biomass hydrogen donation and its high ash content which has potential for deactivating catalytic inorganic elements. The results of this research show that at 50wt% biomass blend ratio, Yunnan coal and oat straw shows the highest synergy while Yunnan coal and rice husk remained additive in behaviour. In addition to this, a degree of synergy inhibition and promotion was observed between the two modes of synergy such that Yunnan coal blends which high catalytic and high non-catalytic synergistic interaction had revealed only 6.1 – 73.8% combined synergy efficiency. The synergy efficiency measures the degree of competition or promotion between the catalytic and non-catalytic synergy modes during the thermal reaction. Whereas Guizhou coal which had insignificant and moderate indication of synergy with organic and inorganic elements of biomass respectively showed up to 1.4 and 5 times multiple of the expected combined synergy. This was resulting from the somewhat overlapping functions of both synergy modes. Lastly, the difference in the efficacy of different biomass inorganic elements during high temperature gasification was observed in the coal and biomass fuel blends. The result obtained indicated that blends with calcium – rich spruce wood revealed negligible improvement compared to potassium rich oat straw due to their restricted mobility on the char surface and their deactivation at higher temperatures >900°C by forming thermally stable calcium oxide. The increase in micro-porosity of the blended fuel’s char was also observed. These fundamental results have provided insights into coal and biomass co-blending behaviour during co-firing and gasification that can be used in aiding the design considerations and optimising the biomass blending ratio to ensure appropriate operation of co-fired fuel reactors. The result revealed that in this study, synergy was highest in the Yunnan coal and oat straw blends at 50:50wt% ratio. This was resulting from the potassium - rich nature of oat straw and low hydrogen content of Yunnan coal, making it a viable proton acceptor in both catalytic and non-catalytic synergy reactions.

Sorption-enhanced catalysts are highly favored to improve the synthesis of methanol by hydrogenation process. This requires the development of selective catalysts and CO2 adsorbents that are sufficiently stable to tolerate cyclic regeneration during operation. The present work focuses on the assessment of the adsorption performance of novel layered double hydroxides acting as supports for copper based catalysts in the reduction of CO2 to methanol. Emphasis is placed on the stability and capacity of hybrids prepared using various preparation routes in order to optimize the CO2 uptake and conversion to methanol per mass of the catalyst. This parameter is crucial in the industrial implementation of the technology as it dictates the size of the adsorption units and reactors required. The co-precipitation of Cu2+, Zn2+ and Zr4+ species onto well-dispersed layered double hydroxides is shown to be an effective preparation method that ensures adequate interaction between the catalysts and the support. Prior to the synthesis of the material, individual enhancement of the catalyst and the LDH template were carried out respectively. The catalysts were prepared via various facile methods. Calcination of the catalysts facilitated the mixture of the Cu catalyst with the respective support bolstering the formation of intermolecular oxo-bridges which resulted to the thermal stability of the catalysts. The thermal performance of the catalysts was directly related to the increase in calcination temperature. However, this temperature was capped at 673K beyond which denaturing of the catalyst occurs. For all given preparation method, comparing the different catalysts based on the Cu-loading, the performance trend is as follows: CP > DP > IM. Other factors experimented to affect the thermal properties of the catalysts include the Cu-loading and heating rate. To improve CO2 adsorption, amine modified Layered double hydroxide (LDHs) were prepared via the conventional, ultrasonic and hydrothermal routes, followed by MEA extraction. A comparative study was conducted with consideration of the effect of functionalization route on the adsorption capacity, regeneration and lifetime of the adsorbent. It is revealed that increase in amount of SDS has an adverse effect on the CO2 adsorption performance by protonating considerable amount of active amino groups. This performance trend was observed across all experimented temperature with the CO2 adsorption capacity decreasing with increase in temperature. After amine modification, adsorption capacity increased by ca. 75-90% and ca.10-30% at 55 oC and 80 oC, respectively. However, by sonochemical modification, the adsorption capacity showed an increase from 12-108% depending on sonic intensity. This is attributed to the enhanced deprotonation of activated amino functional groups via the sonochemical process. Subsequently, this improved the effective amine efficiency by 60% of the conventional. In addition, the sonochemical process improved the thermal stability of the adsorbent as well as reducing the irreversible CO2 uptake, CUirrev, from 0.18 mmol/g to 0.03 mmol/g; hence improving the lifetime and ease of regenerating the adsorbent. This is presented by subjecting the prepared adsorbents to series of thermal swing adsorption (TSA) cycles until its adsorption capacity goes below 60% of the original CO2 uptake. While the conventional adsorbent underwent a 10 TSA cycles before breaking down, the sonochemically functionalized LDH went further than 30 TSA cycles. However, adsorbents prepared via hydrothermal route showed a better CO2 uptake capacity than sonochemical and conventional adsorbents. This is attributed to the decrease in weak basic sites (OH- groups) and moderate basic sites (M-O) and subsequent increase in number of strong basic sites (O2-). Therefore, the sonochemical-assisted hydrothermal treatment promoted the adsorption capacity of the adsorbent. However, the cyclic adsorption efficiency of the hydrothermally prepared sample was lowest ca. 53% compared to 76% and 60% for the sonochemical and conventional process respectively. Adopting the obtained factors for optimum synthesis and operation of both CuO/ZnO/ZrO2 catalyst and Mg-Al LDH adsorbent, a composite catalyst consisting of CuO/ZnO/ZrO2 catalyst on LDH template was synthesised and analysed for CO2 uptake capacity and catalytic activity with variation in Al3+ and Zr4+ compositions. The deposition of the catalyst on the LDH support was found not to alter significantly the CO2 uptake of the hydrotalcites but helps to maintain the surface heterogeneity. Characterization tests shows an improvement in structural modification. However, this is subject to the proportion of the considered varied metals. In addition, despite the high thermal stability of Zr4+, the composite material was observed to weaken in stability with increase in Zr4+ content. Nonetheless, the CO2 uptake capacity was observed to increase. A thorough kinetic analysis demonstrates that the adsorption mechanism is attributed to the chemical nature of the metals which promoted chemisorption as the dominating adsorption mechanism with little contribution from physisorption. CO2 conversion and methanol yield were also dependent on the nature and composition of the cations as well as the operating temperature. Al3+:(Al3++Zr4+) ratio of 0.4 was obtained as the best cation mix to attain maximum methanol yield. A preliminary catalyst screening shows that Cu/ZnO/ZrO2/Mg-Al LDH is a promising candidate to catalyze simultaneous adsorption and reduction of CO2 for methanol synthesis.

Strategies to combat climate change focus on every industry and has led to government policies to reduce electricity generation through coal combustion. Switching to biomass provides an opportunity to use infrastructure constructed for coal combustion with carbon neutral fuels; however, the process of grinding biomass pellets as fuel in pulverised fuel combustion is not well known. 1% of energy generated at a power plant is utilised to achieve the required size for the fuel. Improvements in the understanding of biomass pellet milling could lead to optimisation of operating conditions and minimisation of energy consumption. The process could aid generators determine appropriate fuels and costs for each; this represents a potential opportunity to elongate the life of current power stations, which is more cost effective than construction of new biomass specific plants. This research has developed a population balance equation (PBE) model simulation to predict the output of biomass pellet grinding for Lopulco E1.6 mill and a Retsch PM100 planetary ball mill; this has never been published in literature. It has proven it can predict the output particle size distribution of a Lopulco E1.6 mill, a scale model of an industrial mill, for biomass pellet PSD’s. It has shown that the simulation parameters can be based on axial and flexure deformation testing results, and that it can predict the PSD to within an average 88% accuracy against blind test. A novel technique in evaluating a PSD has been achieved using an overlapping coefficient, a measure better suited to PSD analysis than conventional model validation techniques. The PBE simulation has also shown that back calculating parameters can separate mill and material contributions when utilising a popularly used selection function and a breakage function developed in this research based on the Rosin-Rammler equation. This has been shown for the Lopulco mill and a lab scale planetary ball mill for axial and flexure deformation tests respectively. The research shows that emphasis should be placed on understanding classifier dynamics due to unexpected behaviour in the Lopulco mill experiments. Further conclusions show that energy consumption can be related to axial deformation energy that can be explained by the action of a Lopulco mill’s application of compressive force on and the orientation of pellets against the rollers.

Diminishing fossil fuel reserves and the drawbacks of conventional crop-based biofuels has catalysed recent research into the microbial conversion of lignocellulosic biomass into liquid biofuel. Fatty acids represent the most abundant form of reduced carbon chain in nature, and represent the basic building blocks for the creation of a wide-range of advanced biofuels; such as alkanes, fatty alcohols, and fatty acid methyl- and ethyl-esters. It is hoped that the use of a thermophilic platform strain, that is capable of producing fatty acid-derived biofuels at elevated temperatures, will circumvent some of the challenges faced by established mesophilic organisms such as Escherichia coli or Saccharomyces cerevisiae. Here we describe the heterologous expression of an alkane biosynthesis pathway from the thermophilic cyanobacteria Thermosynechococcus elongatus BP-1 in both E. coli and the thermophilic production organism Geobacillus thermoglucosidasius. Alkane biosynthesis in T. elongatus BP-1 is facilitated by two enzymes: fatty acyl-ACP reductase (AAR) and aldehyde deformylating oxygenase (ADO): both of which were found to demonstrate a level of activity in vivo at mesophilic and thermophilic temperatures (30 - 52°C). Expression of an alkane biosynthesis operon in G. thermoglucosidasius NCIMB 11955 resulted in the production of ~100 mg OD-1 L-1 fatty alcohols, and an inconsistent formation of minute amounts of heptadecane. Improved titres of alkane may be achievable through the identification and elimination of competing pathways, and a better understanding of n-alkane biodegradation in G. thermoglucosidasius. However, we recommend the continued pursuit of fatty alcohol production using G. thermoglucosidasius as a host. Elimination of several fatty acid degradation (fad) genes in G. thermoglucosidasius was undertaken with the hope of showing an ability to manipulate the cellular pool of fatty acyl-ACP substrates available to the alkane biosynthesis pathway. The combined elimination of two long-chain-fatty-acid—CoA ligase genes (fadD1 and fadD2) resulted in increased levels of pentadecanoic- and heptadecanoic acid. The heterologous expression of a fatty acyl-ACP thioesterase (FAT) from Clostridium thermocellum and from the Aminicenantes candidate phylum (OP-8) was also undertaken in an attempt to manipulate levels of cellular FFAs, although we postulate that observation of a differential phenotype requires the development of a strain completely defunct of long-chain-fatty-acid—CoA ligase activity. Fatty acid metabolism in G. thermoglucosidasius represents a complex myriad of multiple genes that are subject to strong homeostasis. Nevertheless, we present evidence that genetic manipulations of G. thermoglucosidasius are sufficient to bring about changes in the fatty acid profile of cells, and encourage the further genetic characterization of fatty acid metabolism in the organism through targeted gene deletions, with the hope of producing an improved platform strain for fatty alcohol and alkane biosynthesis at thermophilic temperatures.

After the oil crisis held in 1973 and 1979, academicians and industry players have noticed the importance and necessity of having alternative and sustainable energy sources in future. Biological wastes, also named as “Biomass” has been cited as one of the significant sustainable energy sources. Biomass poses an ideal and substantial potential to achieve a sustainable system. However, the development of biomass industry is still relatively sluggish due to the lack of confidence of the investor to venture in this relatively new green business. This is most probably attributed to the low-maturation of biomass technologies compared to other conventional technologies, high logistics cost required for biomass transportation and uncertain market penetration barrier for the biomass-derived products. This raises the importance of having a proper biomass management system and a systematic evaluation approach to assess the sustainability performances of the biomass industry. Therefore, the ultimate goal of this thesis is to develop a sustainable multi-biomass supply chain with the aims of optimising all three sustainability dimensions simultaneously. A sustainable multi-biomass supply chain is referred as the integrated value chain of the green products, which derived from various types of biomass, starting from harvesting stage to the final products delivery stage. This thesis discusses in detail on the relevant previous research works toward the introduction of novel evaluation approach to attain different sustainable objectives (i.e., economic, environmental and social) simultaneously. The evaluation approach encompasses various components, including (i) model reduction by using P-graph integrated two-stage optimisation approach; (ii) consideration of vehicle capacity constraint for detailed transportation cost estimation; (iii) integration of various sustainability indexes using various optimisation techniques. On top of that, two novel debottlenecking approaches, one through principal component analysis (PCA) method; while another through P-graph framework, which able to identify and remove barriers that limit the sustainability performance of the biomass supply chain, are proposed. Aside from this, this thesis also aims to reduce the gaps between the researchers and industry players by developing some user-friendly and non-programming-background dependent decision-making tools. Thus, decision-makers are able to understand the insight of their problems easily without requirement of strong mathematical background. A case study in Johor, a southern state in Malaysia, which is endowed with extensive biomass resources, is used to demonstrate the effective of the proposed approaches.

Biomass utilisation as a fuel in power generation has become an increasingly attractive prospect due to legislation and consumer awareness surrounding fossil fuels and their effect on climate change. However, a large portion of the world relies upon energy produced from readily available local coal sources. Large quantities of these local coals have low combustion efficiencies and energy outputs. An investigation was conducted to improve the combustion performance of these unreactive coals through the addition of small quantities of biomass in co-fired pulverised fuel conditions. To assess whether unreactive coal co-fired with biomass produced improved combustion performance a study of slow heating interactions was undertaken. Through the use of laboratory thermal conversion techniques, thermogravimetric analysis and horizontal tube furnace, slow heating ramp rates were achieved. Samples blended on a 50% coal loading experienced these conditions. Slow heating pyrolysis on a 50% coal loading displayed no synergistic improvement to VM content of coal blended with biomass, whilst catalytic increases of char reactivity were observed for coal blended with high ash biomass species through burn-out testing, such as OC. Following the baseline observations for slow heating conditions, blended samples were subjected to fast heating ramp rate conditions, through the use of a drop tube furnace. At fast heating pyrolysis conditions on a 50% coal loading synergistic improvements of VM yield were observed for coal blends with low ash biomass species, such as W. High ash biomass species showed minimal evidence of synergetic increase to VM, instead displaying the catalytic improvements to char burn-out performance, as seen with slow heating rates. A trail of varying coal loading ratios was conducted to determine the quantity of biomass required to observe the greatest improvements and to ascertain the viability of findings at industrially relevant conditions. Synergistic improvements in VM yield were caused by a steam gasification mechanism during fast heating ramp rates whilst catalytic improvements were caused by the presence of high quantities of alkali and alkaline earth metals (AAEMs). Fast heating rate coal blend trials conducted with partially demineralised biomass fuels provided a deeper understanding of the influence that AAEMs had on char reactivity. A regression analysis provided a quadratic model that demonstrated a strong relationship between AAEMs and char reactivity, with a correlation coefficient R2 value in excess of 95%. A fast heating rate combustion test was conducted to determine whether improvement to ignition distance could be achieved through co-firing. Both qualitative and semi-quantitative analysis of the captured particle images were inconclusive as to improvements in ignition distance.

This thesis investigates the process conditions, charcoal composition and biomass sources for process development of BBQ charcoal briquette production. This aim has been achieved by three areas of investigation: 1. Experimental pyrolysis at lab and pilot scale, with the aim of determining optimal process conditions and if addition of low cost catalyst material is beneficial to slow pyrolysis. 2. BBQ charcoal combustion and modelling of the fire temperature history to determine the pyrolysis conditions and allowable concentrations of non-charcoal additive important to the final charcoal briquette. 3. Techno-economic and carbon analysis (TEA) of the various options for by-product utilisations and determination of important process conditions. The novel findings from the experimental and modelling studies add to the literature on catalytic slow pyrolysis and lump char combustion, whilst applying these concepts to present optimal process flows and conditions for BBQ charcoal production. 1. The addition of low cost acidic and basic catalyst such as bentonite clay or dolomite to the slow pyrolysis of biomass can significantly increase the charcoal yield, and significantly improve the process economics. This also improves the quality of by-product liquid, high in low molecular weight phenolic compounds. 2. Lump charcoal combustion in a grate burner can be simulated by applying the analogy of a two first order chemical reactions in series model to the temperature profile of a simple combustion experiment. The model only requires proximate analysis of the charcoal briquette, and is valid up to briquette mixtures containing 30% inert or raw biomass additive. 3. Temperatures, around 450°C, are required. Lower temperature increases charcoal yield and therefore process economics and this is not too low to produce poor quality charcoal. 4. Processes either A) utilising the gas and liquid by-products in a combined heat and power engine or B) recovering the chemical stream as phenolic oils and using the gas stream to produce heat are the most economic and carbon efficient outcomes. 5. Addition of clay minerals are key to the economic success of both processes by increasing charcoal yield and producing better quality oil high in low molecular weight phenolic compounds.

Many parts of the World have remained underdeveloped due to the lack of access to electricity. Developing and promoting alternative energy sources from renewable materials would assist to mitigate the energy crisis in many parts especially in the World. This research examined the possibility of using a 10KW power pallet as a sustainable energy generation system especially for energy poor areas. This was achieved through the gasification of woodchips at varying moisture content, varying gasification times and at varying electrical loads while investigating the numerous changes in the major factors affecting gasification such as temperature, fuel consumption rate, equivalence ratio (ER), quality of the producer gas, heating value, carbon conversion efficiency as well as the cold gasification efficiency of the gasifier. Experimental data was analysed and interpreted by one way Analysis of Variance (Anova) to establish a relationship on the effect of the major factors affecting gasification as investigated in this study. It was discovered that the gasifier is an autothermal system that maintains a steady state of thermodynamic equilibrium for longer hours as long as the gasifier is constantly supplied with a drier fuel. The gasifier stably and optimally operates with woodchips of moisture content less than 10% to produce an energy rich gas for gasification times longer than six hours to yield a gas rich in Hydrogen (H2), Carbon monoxide (CO) and methane (CH4) at a respective concentration of up to 18.1%, 25.3% and 2.2% with a corresponding Higher Heating Value (HHV), Cold Gas Efficiency (CGE) and gas production rate of 6.4MJ/m3, 75.8% and 2.34m3/kg respectively. The reactor takes longer time to attain thermodynamic equilibrium once operated with woodchips of moisture content above 15%. This subsequently affects the quality of producer gas yielding a gas of low calorific value that would even clog the engine. The moisture content of the wood chips was found to play a very significant role in determining the values of temperatures attained and subsequently determining the quality of producer gas. The gasifier was found to produce the required energy up to the design capacity of 10KW required for several industrial applications. Increasing the engine throttle valve increased the frequency of the engine and subsequently the voltage. The designed energy output of up to 10KW could only be produced if the engine frequency was 60HZ and could be lower if the engine operated at a lower frequency. A thermodynamic equilibrium model was further developed to predict the composition of producer gas going to the engine. The thermodynamic equilibrium model yielded a gas composition of 25.99%, 23.92%, and 0.42% for CO, H2 and CH4 respectively that was in good agreement with the experimental results at 850 ºC and ER of 0.27. Similarly, the modelled gasification temperature of 870.85ºC corresponds with a minor deviation of 2.5% with the experimental gasification temperature of 850ºC. The exhaust stream composition contained Carbondioxide (CO2) of upto 20% which is on the higher side because air was used as the gasifying agent and the gasifier was completely autothermal. Such CO2 concentration ought to be lowered if the gasifier is to be adopted as a sustainable renewable energy system. The gasifier was found to operate better with wood chips in the size range between 1.3cm - 4.0cm as very fine wood chips would block the flow of air hence compromising on the sustainability of the exothermic reactions and bigger wood chip particles would not be easily broken down by the auger hence resisting the flow of the woodchips into the reactor. Operating the gasifier at optimal conditions yields a gas of high calorific value good enough to make it a reliable standalone system that could be integrated into sustainable bioenergy systems.

Clostridium autoethanogenum is an important organism for biofuel production. Other 'omics' approaches have been used to understand the mode of operation of the organism but metabolomics gives information on the cellular activities in the cell. Metabolomics combined with other 'omics' data can provide a deeper understanding for pathway interpretation. This project sets out to develop an analytical method that is suitable for analysis of highly charged polar compounds found in C. autoethanogenum metabolic pathways. Also investigate suitable isotope labelled internal standards to improve matrix effects to the metabolites as a result of the biological matrix. A high-throughput hydrophilic interaction liquid chromatography isotope dilution mass spectrometry (HILIC-IDMS) was developed and validated using high resolution hybrid orbital trap MS for both targeted and untargeted metabolomics analysis of intracellular metabolic pathways of Clostridium autoethanogenum. Extraction of intracellular metabolites from C. autoethanogenum was achieved using a specifically developed sample preparation protocol using freeze thaw cycles (freeze in liquid nitrogen and thaw on ice repeated 3x). A total of 133 metabolites were monitored and validated. Limits of detection (LODs) ranged from 0.001 µM to 5 µM reported for compounds such as NADPH and NADH. Limits of quantification (LOQs) for all metabolites ranged from 0.001 µM to 10 µM for metabolites such as glucose-6-phosphate and glyceraldehyde-3 phosphate. Precision and accuracy were evaluated for all metabolites and found to be within the acceptable limits of ±15 % with few exceptions for some nucleotides and organic acids. Stable isotopically labelled internal standards were generated from C. pasteurianum cells that provided coverage for about 100 metabolites. This enabled absolute intracellular concentrations to be obtained in combination with the estimated cell volume of C. autoethanogenum that was obtained from microscopy and flow cytometry measurements. The developed HILIC-IDMS method was applied to various solvent production optimisation experiments conducted using C. autoethanogenum and the main findings are reported below. In chapter 4, the HILIC-IDMS method was applied to C. autoethanogenum in an experiment where the pH of the media was reduced to improve ethanol and solvent production. The metabolomics studies of this experiment gave intracellular concentrations that differentiated the acidogenic phase from the solventogenic phase. A total of 86 metabolites were quantified in this experiment. Intermediates in the tricarboxylic acid (TCA) cycle were the most affected during the acidogenic/solventogenic transition. Metabolites concentrations were used for metabolic pathways analysis to understand the pathways affected during the pH shift. The pathway analysis also confirmed the TCA cycle was the most affected pathway during the acidogenic/solventogenic transition. In chapter 5, The HILIC-IDMS method was applied to a gas shift experiment to optimise ethanol and solvent production. Gas shift is another approach that can be used to optimise solvent production in similar as the pH shift experiment. The use of gas shift to induce solventogenic phase can be difficult as C. autoethanogenum has little tolerance for high levels of CO hence the increase in gas (CO) flow rate has to be done in a gradual fashion. Equally, TCA intermediates were observed to be the most affected as observed in the pH shift experiment. In chapter 6, the method was applied to a study where pantothenate and phosphate concentrations in the growth media of C. autoethanogenum were reduced to increase ethanol production. Pantothenate is the precursor for coenzyme A (CoA) production and metabolomics study confirmed a decrease in CoA concentration when pantothenate concentration was reduced. Metabolomics also showed decrease in concentration of metabolites directly linked to CoA synthesis such as L- Aspartate. Metabolic pathway analysis also confirmed the pantothenate and CoA biosynthesis and its associated pathways were the most affected pathways during the pantothenate-limiting phase. Both targeted and untargeted metabolomics analysis were performed on these nutrient-limiting experiments and there were clear differences between the two different conditions before and after nutrient limitation. Supervised multivariate data analysis using OPLS-DA was used to compare higher pantothenate and low pantothenate concentration and there were clear separation and clustering between the two conditions. Cross validation obtained for R2Y and Q2 were 0.993 and 0.941 respectively. OPLS-DA plots for phosphate limitation also showed clustering and separation between the high phosphate concentration and reduced phosphate concentration with R2Y and Q2 0.981and 0.837 respectively. In conclusion, a novel high-throughput HILIC-IDMS method was developed and validated for analysis of different classes of polar compounds in bacteria. The method has the potential to be applied in other biological matrices for coverage of diverse range of polar compounds.

Graphene is a relatively new carbon material increasingly finding technological applications due to its unique physical and engineering properties. Here, its application as catalyst for the oxygen reduction reaction (ORR) in alkaline media is investigated. First, the role of graphene-related materials (including multi-walled carbon nanotubes) as catalyst supports is compared to the widely used carbon black, finding that the ORR follows a mixed behaviour between the direct 4-electron pathway and the indirect 2-step mechanism on graphene-supported platinum catalysts. Further, different combinations of boron, nitrogen, phosphorus and sulphur metal-free doped-graphene catalysts have been systematically synthesised and evaluated, finding that dual-doped graphene catalysts yield the best ORR performance. Specifically, phosphorus and nitrogen dual-doped graphene (PN-Gr) demonstrates the highest catalytic activity, with 3.5 electrons transferred during the ORR. Doped-graphene/perovskite oxide hybrid catalysts have been also tested, yielding PN-Gr/La0.8Sr0.2MnO3 the best ORR activity in terms of measured current density, achieving a value that is 85% of that reported for a commercial Pt/C catalyst. Moreover, SN-Gr/La0.8Sr0.2MnO3 produces the lowest amount of peroxide formation with only 10%. These results confirm the graphene-derived catalysts as promising alternatives to the current platinum-based catalysts, and could enable the important issues related to its practical application to be overcome.

Being one of the highly explored nanomaterials, graphene and derivatives are in the limelight of scientific research. The quest of mass production of graphene in a fast, eco-friendly and economical way lead to different greener synthesis approaches with reduced risk and harm to the environment. Here through this investigation, different greener approaches in the preparation of graphene and its derivatives were analysed. Moreover, the biocompatibility of the product is analysed for ensuring the safety while introducing as a biomaterial to a living system. The initial part of the study, a hydrothermal reduction method was utilized to reduce graphene oxide (GO) to create reduced graphene oxide (RGO) without using any toxic reducing agents. Following this, with the use of a variety of ultrasonic cavitation, a profoundly stable ( > 2 year) few layer thick RGO nanodispersion was generated without employing any stabilizers. The excellent stability at physiological pH promotes its utilization of RGO dispersion as a carrier of Paclitaxel (Ptx) – an anticancer drug. The in vitro cytotoxicity analysis of the Ptx loaded RGO nanodispersion revealed the potential of the nanodispersion as a suitable drug carrier. RGO dispersion is also utilized in combination with glucose oxidase (GOD) enzyme, for the detection of glucose. RGO-GOD modified working glassy carbon (GC) electrode was evaluated to analyze the redox reaction in the presence of oxygen. This investigation demonstrated the potential of the exceptionally stable RGO nanodispersion in nano drug delivery and electrochemical sensing applications. Development of RGO nanodispersion through ultrasonication lead to the idea of creating graphene (G) sheets from graphite through ultrasonic exfoliation. Upon success of the G production, the next part of the research focused on the sonochemical development of graphene-gold (G-Au) nanocomposite through simultaneous exfoliation of graphite as well as the reduction of gold chloride. The G-Au nanocomposite was well characterized and utilized to fabricate an electrochemical sensor for the selective detection of nitric oxide (NO), a critical biomarker associated with numerous physiological and pathological abnormalities. The cytotoxic effects of the sonochemically synthesized G, AuNPs and G-Au nanocomposite were conducted on mammalian cell lines revealed the selective cytotoxic effects towards cancer cells and biocompatible nature towards normal cells. Biocompatibility results supported the use of the G-Au nanocomposite system for anticancer applications such as drug delivery, imaging, etc. Next part of the research used a natural reducing agent for reducing GO to RGO, utilizing a medicinal mushroom- Ganoderma lucidum (G.l.) extract. Similarly reduced graphene oxide-silver (RGO-Ag) nanocomp osite also was prepared by the facile one-step synthesis method. The properties of RGO-Ag obtained were well characterized and tested for sensing of hydrogen peroxide (H2O2), a cancer biomarker. Similarly, the antimicrobial potential of RGO-Ag was tested on different bacterial species. Furthermore, the cytotoxicity of RGO-Ag was tested on mammalian cell lines exhibited good biocompatibility. The sensing studies revealed the potential of RGO-Ag in H2O2detection. The antibacterial studies of RGO-Ag displayed comparable results with standard antibiotic Chloramphenicol. The antibacterial effects, sensing potential and selective toxicity towards cancer and normal cells make this RGO-Ag nanocomposite a promising candidate for future health care industry. Last part of the study focused on an electrochemical biosensor for the detection of cancer. Nanomaterials in combination with biomolecules are used in drug delivery, imaging and sensing applications by targeting the overexpressed cancer proteins such as folate receptors (FR), to control the disease from progressing to advanced levels. Here, a biocompatible RGO nanosheets (produced using G.l. extract) in combination with folic acid (FA), a vitamin with high bio-affinity to FR, is utilized for the development of an electrochemical sensor for the detection of cancer. The formation of RGO-FA nanocomposite was confirmed by various characterization techniques. The RGO-FA modified GC electrode was analysed by differential pulse voltammetry (DPV) for its accurate detection towards FR. This RGO-FA modified electrode showed good specificity and reliability when tested against similar interfering biomolecules. This RGO-FA sensor offers a great promise to the future medical industry through its highly sensitive detection of FR in a fast, reliable and in an economical way.

Ammonium dinitramide as non-corrosive, high performance, and Eco-friendly propellant was first synthesized by Russians in early 1970s, and then independently in early 1990s by Stanford Research International. Since then, there has been increased interest in its synthesis and performance analysis. Therefore, this project was aimed to enhance the study of ADN and explore new areas of its application. This project has 3 objectives where syntheses, prilling, electrolysis of ADN were studied. In first objective, a new, modified ADN synthesis method was developed. This method was able to synthesize ADN at near-zero temperature by nitration of potassium sulfamate with mixture of nitric acid, sulfuric acid and trifluoroacetic acid. Once synthesized, parametric studies were performed to increase the reaction yield. It was developed by analyzing the existing ADN synthesis methods and their reaction mechanisms. In the second objective, ADN prilling and sonication was performed via ultrasound treatment and the results were compared with ADN obtained by existing methods. It was necessary to perform prilling i.e. conversion of ADN crystal morphology because, ADN in its raw form have long needle like structure. Secondly, it has low critical humidity level of ADN i.e. 55.2%RH renders practical and handling issue in humid climate. Therefore, an ultrasound based prilling and coating method was developed, where ADN was sonicated in toluene as sonication medium along with surfactants and coating polymers. With this method, it was possible to combine prilling and coating of ADN particles into single step with results comparable to conventional melt prilling method. In third objective, ADN based liquid monopropellant named FLP-103 was electrolytically decomposed and its performance was analyzed in micro thrusters. In order to decompose ADN by electrolysis, Micro thrusters were fabricated with Polydimethyl siloxane (PDMS) and the experiments were analyzed by video footage, load cell thrust measurement and self-fabricated thrust measurement system. The thrusters were fabricated using combination of embossing and engraving techniques with PDMS to eliminate leakages and backpressure. Thrust measurement system, based on PDMS made torsion rod was developed as a proof of concept by using low cost sensors LDC-1000 from Texas instruments. Its results were compared with the results obtained by load cell thrust measurement. The results showed that ADN can be successfully decomposed via electrolysis in micro thrusters and electrolysis occurs predominately at cathode.

Biomass is one of the renewable energy resources that has carbon in its building blocks that can be processed into liquid fuel. Napier grass biomass is a herbaceous lignocellulosic material with potentials of high biomass yield. Utilization of Napier grass for bio-oil production via pyrolysis is very limited. Bio-oil generally has poor physicochemical properties such as low pH value, high water content, poor chemical and thermal stabilities which makes it unsuitable for direct use as fuel and therefore requires further processing. Upgrading of bio-oil to liquid fuel is still at early stage of research. Several studies are being carried out to upgrade bio-oil to transportation fuel. However, issues regarding reaction mechanisms and catalyst deactivation amongst others remain a challenge. This thesis gives insights and understanding of conversion of Napier grass biomass to liquid biofuel. The material was assessed as received and characterized using standard techniques. Pyrolysis was conducted in a fixed bed reactor and effect of pyrolysis temperature, nitrogen flow rate and heating rate on product distribution and characteristics were investigated collectively and pyrolysis products characterized. Effects of different aqueous pre-treatments on the pyrolysis product distribution and characteristics was evaluated. Subsequently, in-situ catalytic and non-catalytic, and ex-situ catalytic upgrading of bio-oil derived from Napier grass using Zeolite based catalysts (microporous and mesoporous) were investigated. Upgraded bio-oil was further fractionated in a micro-laboratory distillation apparatus. The experimental results showed that high bio-oil yield up to 51 wt% can be obtained from intermediate pyrolysis of Napier grass at 600 oC, 50 oC/min and 5 L/min nitrogen flow in a fixed bed reactor. The bio-oil collected was a two-phase liquid, organic (16 wt%) and aqueous (35 wt%) phase. The organic phase consists mainly of various benzene derivatives and hydrocarbons while the aqueous phase was predominantly water, acids, ketones, aldehydes and some phenolics and other water-soluble organics. Non-condensable gas (29 wt%) was made-up of methane, hydrogen, carbon monoxide and carbon dioxide with high hydrogen/carbon monoxide ratio. Bio-char (20 wt%) was a porous carbonaceous material, rich in mineral elements. Aqueous pre-treatment of Napier grass with deionized water at severity factor of 0.9 reduced ash content by 64 wt% and produced bio-oil with 71 % reduction in acid and ketones. Performance of mesoporous zeolites during both in-situ and ex-situ upgrading outweighed that of microporous zeolite, producing less solid and highly deoxygenated organic bio-oil rich in alkanes and monoaromatic hydrocarbons. The Upgraded bio-oil produced 38 wt% light fraction, 48 wt% middle distillate and 7.0wt% bottom product. This study demonstrated that bio-oil derived from Napier grass can be transformed to that high-grade bio-oil via catalytic upgrading over hierarchical mesoporous zeolite.

This study focuses on the utilization of solid carbonaceous wastes, the mitigation of CO2 and the development of CO2-based chemical production process which is divided into three main parts. The first part consists of the investigation of solid carbonaceous samples behaviours under pyrolysis and combustion processes. The second part covers experimental study of CO2 gasification aiming at the identification of interactions during co-gasification. Here, the presence of interactions will be further discussed, particularly in terms of increasing the gasification rate of low reactive carbonaceous sample and the effect of pyrolysis heating methods on gasification reactivity. The last part considers the thermodynamic assessment of conventional and CO2-enhanced biomass gasification. The objective is to identify the influence of CO2 as a gasifying agent in biomass gasification. Moreover, the comparisons study of bio-DME production based on conventional and CO2-enhanced gasification was also carried out in this thesis. (i) Pyrolysis of NMPCBS and combustion of solid carbonaceous materials This part consists of investigation of solid carbonaceous samples behaviours under pyrolysis and combustion processes. The objective is to explore the feasibility of the utilization of non-metallic part of waste printed circuit boards (NMPCB), including the thermal behaviours of NMPCB and its blends with two types of coals by using a thermogravimetric analyser (TGA). For individual sample, the results showed that the NMPCB had the fastest rate of pyrolysis and the highest maximum weight loss rate compared with coals, thus, the highest reactivity. These were attributed to the thermal degradation properties of the constituent elements in NMPCB. Meanwhile, based on kinetic study, it is evident that the lower heating rates favoured the pyrolysis process. For blends, it was revealed that there was 6%-7% deviation in terms of the yield of solid residue between experimental and calculated values, indicating a significant gap between the overall activation energy (Ea) of the blends and its average (Eave). Thus, it confirmed the existence of interactions in co-pyrolysis. Moreover, the combustion characteristics of an Australian coal, a suite of solid carbonaceous materials, and their blends were also investigated. A drop in both ignition temperature and burnout temperature was observed when carbonaceous wastes were blended with coal at different proportions (10 wt% and 30 wt%) which justified that there were strong interactions during the co-processing of coal with carbonaceous materials. The ignition index values of coal/polystyrene and coal/oat straw blends increased by 78% and 52%, respectively, when the blending ratio increased from 10 wt% to 30 wt%. Similarly, 2.6 times increase in combustion index was also observed in coal/oat straw blend. The presence of interactions in blends was further measured by using the root mean square interaction index (RMSII) which showed that coal/oat straw and coal/polystyrene blends had the highest RMSII values. This indicated the presence of strong interactions during co-combustion. (ii) CO2 gasification of solid carbonaceous materials The second part covers the feasibility evaluation of using CO2 as a gasifying agent, namely CO2 gasification, for various solid carbonaceous materials. The work includes the conversion of carbonaceous materials to syngas, gasification characteristics of coal, a set of waste carbonaceous materials, and their blends. The experiments were run by using a thermogravimetric analyser (TGA). The results showed that CO2 gasification of polystyrene completed at 470 °C, which was lower than those of other carbonaceous materials. This behaviour was attributed to the high volatile content coupled with its unique thermal degradation properties. Further results demonstrated that CO2 co-gasification process was enhanced as a direct consequence of interactions between coal and carbonaceous materials in the blends. The intensity and temperature of occurrence of these interactions were influenced by the chemical properties and composition of the carbonaceous materials in the blends. The strongest interactions were observed in coal/polystyrene blend at the devolatilisation stage, as indicated by the highest value of RMSII, whereas at char gasification stage, the highest interactions were found in coal/oat straw blend. The catalytic effect of alkali metals and other minerals in oat straw, such as CaO, K2O, and Fe2O3, contributed to these strong interactions, thus, the addition of polystyrene and oat straw enhanced the overall CO2 gasification of coal. On the other hand, interactions between petroleum coke and solid carbonaceous materials were also analysed with the aim of enhancing the gasification reactivity of highly unreactive petroleum coke. To achieve this, an Australian coal and gum wood were chosen for co-processing with petroleum coke. The addition of gum wood was found as the significant contributor of the enhanced gasification reactivity of petroleum coke. This is due to the combined influence of a number of unique features of bio-char, such as high surface area, more active sites, low crystalline index and the catalytic effect of alkali and alkaline earth metals (AAEM) compounds. These results confirmed that proper selection of solid carbonaceous materials for gasification of petroleum coke is an effective means to improve the conversion efficiency of petroleum coke, i.e., higher reactivity, and therefore expand its large scale utilization. In addition to coal and petroleum coke, the isothermal and non-isothermal CO2 gasification of an algal biomass (Chlorella) char were also carried out by using TGA under two different heating systems, i.e. conventional and microwave-assisted pyrolysis. Based on reactivity index, maximum peak temperature and maximum mass loss rate parameters, it was shown that microwave char had higher gasification reactivity than that of conventional char. Likewise, the activation energy value of microwave char also confirmed its higher reactivity which was found to be about 9.6% lower than that of conventional char. In addition, the physical properties of these chars, such as Brunauer-Emmett-Teller surface area, carbon crystalline structure and number of active sites, were systematically tested. Based on these properties, microwave char was found to be more reactive as demonstrated by its large BET surface area, low crystalline index and high active sites. Meanwhile, co-gasification experiments under isothermal condition revealed the existence of greater synergistic effects in coal char/microwave algae char blend than that present in coal char/conventional algae char blend. (iii) Process modelling and simulation The last part considers the process simulation of thermodynamic assessment for CO2-enhanced biomass gasification. The primary objective is to identify the influence of CO2 as a gasifying agent in biomass gasification. In this part, steam and CO2-enhanced gasification of rice straw was simulated using Aspen Plus simulator and compared in terms of energy, exergy and environmental impacts. It was found that the addition of CO2 had less impact on syngas yield than gasification temperature; the cold gas efficiency (CGE) increased with CO2/Biomass ratio. At lower ratios (below 0.25), gasification system efficiency (GSE) was below 22.1%, which is lower than that of conventional gasification. However, when CO2/Biomass ratio was increased, the GSE continued to increase and reached a peak of 58.8% at ratio of 0.87. In terms of syngas exergy, the value generally increases with CO2 addition mainly due to the increase in physical exergy. In this work, chemical exergy was found to be 2.05 to 4.85 times higher than physical exergy. The maximum exergy efficiency occurred within the temperature range of 800 oC to 900 oC, related to the peak of syngas exergy. For CO2-enhanced gasification, exergy efficiency was found to be more sensitive to temperature than CO2/Biomass ratios. In addition, the preliminary environmental analysis showed that CO2-enhanced gasification resulted in significant environmental benefits compared with stream gasification. However improved assessment methodologies are needed to better evaluate the advantages of CO2 utilization.

The world faces unprecedented challenges in mitigating climate change and reducing CO2 emissions from fossil fuel utilisation has been clearly taken as one of the major climate change mitigation strategies. Among the carbon capture technologies, solid adsorbent looping technology (SALT) using activated carbon is considered to be one of the most promising methods due to the extensive sources raw materials, low price, high specific surface area and low energy requirement for regeneration. Synthesis of activated carbons with high adsorption capacity and CO2/N2 selectivity for post combustion capture (at a low CO2 partial pressure and high temperature) is the focus of current research on carbons. This project aims to utilize abundant and easy access materials such as biomass or polymers as precursors and alkaline metal based compounds as activating agents to prepare novel activated carbons with exceptional CO2 adsorption performance to meet the requirement of post combustion CO2 capture in power plants. Two kinds of precursors, biomass (rice husk) and polymer (polyisocyanurate foam), were employed to prepare effective activated carbons for post-combustion CO2 capture. A novel cost-effective methodology able to achieve the carbonization, chemical activation and simultaneous surface functionalization essentially in a one-step process were developed. The work on carbons derived from rice husk (RH) showed that the synthesised bio-carbons exhibit exceedingly high ultra-microporosity, accounting for up to 95% of total porosity. With a modest surface area of 1035 m2/g and a total pore volume of 0.43 cm3/g, the best performing RH carbon showed a record high and fully reversible CO2 uptake capacity of 2.0 mmol/g at 25 oC and a CO2 partial pressure of 0.15 bar, which was the highest uptake ever reported for bio-carbons. Furthermore, it was attempted to tablet precursors with different compacting pressures before activation in order to further improve the adsorption performance. The results showed that the compacted rice husk-derived carbons exhibited much higher ultra-microporosity, especially volume of pores smaller than 0.42 nm and a large amount of mesopores. This has led to exceedingly high CO2 uptake, up to 6.80 and 4.50 mmol/g at 0 and 25 °C respectively and 1 bar and 1.90 mmol/g at 25 °C and a CO2 partial pressure of 0.15 bar, which was much higher than samples prepared at 700 °C without compaction. Meanwhile, the compacted samples showed much higher initial slope (IS) CO2/N2 selectivity up to 170 at 25 °C while the selectivity of the sample prepared at 700°C without compaction was only 56. Polymer-derived carbons also showed exceedingly high levels of ultra-microporosity and unique surface chemistry for CO2 adsorption. The resulting ultra-microporous carbon foam achieved a record-high CO2 uptake of 2.12 mmol/g at 25 °C and 0.15 bar as well as a record-high CO2/N2 selectivity of 200, which is among the highest ever reported for porous carbon materials and most MOFs. In addition, the adsorption performance of samples at flue gas conditions (0.15 bar CO2 and 40-50 °C) were also studied. The samples showed record-high CO2 uptake of about 2 mmol/g at flue gas condition (40-50°C and 0.15 bar CO2), which was higher than any carbon materials from more sophisticated and cost-prohibitive methodologies, most zeolites and MOFs. The polymer-derived carbons investigated here exhibited fast adsorption kinetics and excellent stability and regenerability under simulated flue gas condition. Further studies in this project showed that the excellent performance of carbons from different precursors can be attributed to ultra-microporosity and favourable surface chemistry achieved by the facil one-step synthesis. The CO2 adsorption capacity is associated with the pore volume of pores smaller than a specific size, which varied with the temperature and partial pressure. The ultra-micropore volumes of pores smaller than 0.44 nm and 0.40 nm is responsible for the CO2 adsorption at 0.15 bar 25 °C and 50 °C respectively. In addition to ultra-micropores, this work showed that surface potassium groups on surface identified by EDX and XPS could significantly improve the CO2 adsorption performance, especially at low partial pressures. As for RH carbons, up to 50% of the total CO2 uptake was attributable to the unique surface chemistry, which appears to be dominated by the enhanced formation of extra-framework potassium cations, owing to the presence of zeolitic structures incorporated within the carbon matrices. The work on polymer derived carbons showed that there was a linear relationship existing between CO2 adsorption capacity and surface potassium content, while no direct relationship between nitrogen containing groups and CO2 adsorption capacity was observed. Meanwhile, the high heat of adsorption and IS selectivity also indicated the strong surface affinity to CO2. Overall, the prepared potassium doped carbons possess great potential as adsorbents for post combustion CO2 capture.

Biomass is used for fuel by humanity from prehistoric times. With the passage of time and to meet the energy needs, non-conventional ways of utilizing the conventional sources became an interest with use of technologies. Biomass gasification is a proven technology that can economically use alternative energy resource of “Carbon Neutral”. Biomass product gas from biomass gasification is composed of CO, CO2, CH4, H2, other hydrocarbons, traces of other components and tar from biomass gasification. Fluidized bed gasification is one of the promising technologies to achieve high thermal conversion efficiency as it takes great advantages of fluidization in terms of uniform temperature profiles and excellent gas-solid interactions. The present research is aimed to evaluate the performance of a bubbling fluidized bed biomass gasifier for product gas production composition using air as gasification agent and SRC willow chips as biomass. Particle capture efficiency of the mop fan and an effect of different operating conditions such as bed temperature, equivalent ratio on the product gas composition and heating value are also investigated at Institute of Sustainable Energy Technology, University of Nottingham. The concentrations of particulate matter in the product gas before and after the mop fan cleaning unit are measured to assess the performance of the cleaning unit. Different fan rotating speeds and different flow rates of spray water are used to optimise the particle removal efficiency of this unit. It has been found that the mop fan cleaning unit has achieved an efficiency of 90% in removing particle matters and an efficiency of more than 80% in removing N-species presented in the product gas. Tars appear as a major issue in the product gas and should be removed from the product gas before they get condensed in the equipments which utilise product gas. Tar arrest techniques were successfully tested in this investigation such as woodchips bed, water spray and mop fan. The synergic effect of tar removal of water spray and mop fan found to be more effective in removing tars as if used individually. Different spray water amounts were used with a constant fan speed for keen observation of tars’ solubility in the water and found reasonable removal of tars from product gas.

The focus of this paper is to investigate the production of activated carbon from biomass on laboratory (lab) and pilot scales. Different biomass sources (> 30) were pyrolysed and steam activated on a lab scale to assess final quality. These were reduced to six based on potential, which were then activated under different temperatures and residence times to develop an analysis matrix. From this and other set criteria, olive stone and pine wood - a granular and powder carbon respectively - were chosen. The biomass chars were tested and compared under many production variables in lab and pilot scale production. Further novel findings: Linear burn off rates were seen by increasing activation temperature residence time, and an exponential burn off by increasing water flow. In both lab and pilot scale there was direct linear correlation between burn off percentage and CTC (carbon tetrachloride activity) values for both biomasses proving scalability, this was maintained as porosity changed with increasing burn off. The maximum CTC value for olive stone was found to be 84.5 at 74% burn off using activation conditions of 775 oC, 120 minutes and 1.125 ml/min water flow rate. Pine wood produced a peak CTC value of 120 at 80% to 82% burn off using activations conditions of 800 oC, 90 minutes and 1.5 ml/min water flow rate. Both carbons produced a higher CTC than a tested commercial carbon (60). The CTC values curtailed after > 80% and > 85% burn off for olive stone and pine wood respectively due to destruction and high ash to carbon ratios. Methylene blue numbers were seen up to 22 (330 mg/g) and 25 (375 mg/g) for olive stone and pine wood respectively. Olive stone produced surface areas up to (1157 m2/g) micropore volumes (0.458 cm3/g), mesopore volumes (0.317 cm3/g) and total pore volumes up to (0.753 cm3/g) with this surface area, mesopore volume and total pore volumes were the highest found in literature for steam activation. Pine wood produced surface areas up to (1190 m2/g), micropore volumes (0.472 cm3/g), mesopore volumes (0.589 cm3/g) and total pore volume to (1.061 cm3/g), all higher than any current reported values using steam activation. Production variable limits prior to excessive burn off were found for both biomasses: Activation temperatures over 850 oC and 825 oC for olive stone and pine wood respectively, olive stone with a residence time of > 6 hours and steam flow rate of > 1.875 ml/min whereas there proved to be no adverse effects to long residence times and high steam flow rates with pine wood. This was deduced to be due to a higher mass transfer limitation seen with the higher density olive stone resulting in external particle ablation. Single step production was carried out on lab and pilot scale with no negative effects seen to adsorption properties and pore structures. The produced carbons was comparable to the products produced by the usual two-step process. Calcium oxide ash component in pine wood is lost during production proved by ion chromatography analysis. Hot water washing biomass had no effect on the burn off percentage, CTC correlation only on the individual burn off percentage and total yields of the carbons. An OPEX/CAPEX cost analysis was completed and showed that both carbons are potentially profitable products.

Functional food ingredients such as prebiotics are emerging as effective tools for managing the risks associated with gastrointestinal diseases and gut related dysfunctions. This work explores the production of prebiotic rich extracts from two sources of lignocellulosic biomass – energy crop \(Miscanthus\) \(χ\) \(giganteus\), and oat (\(Avena\) \(sativa\)) husks, an agricultural by-product. Whilst most of the research to date has been focusing on the utility of cellulose, the hemicellulose and lignin fractions have been underutilised. This work expands the value of the hemicellulose fraction by extracting the prebiotic xylo-oligosaccharides (XOS) and other hemicellulose derived products using environmentally benign sub-critical water in a 0.5 L stirred batch reactor at temperatures between 120-220°C with residence times 0-77 min, and 0.5-13% (w/v) biomass loading. The extracts were analysed with HPAEC-PAD, HPLC and colorimetric assays. Almost complete hemicellulose solubilisation was achieved, and highest yields of prebiotic (DP 2-5) XOS were observed at 170°C and 35-77 min corresponding to 44-56% with little amounts of carbohydrate degradation products and low total phenolic contents. Although higher yields were achieved with oat husks, the XOS extractability was comparable between the biomass sources. Higher extraction severities resulted in further XOS depolymerisation into monosaccharides and eventual formation of furfural and 5-HMF.

Algae have been studied as a potential biodiesel feedstock by identifying on a global scale suitable cultivation locations for three specific cases (EU, US and Brazil) based on the area requirements. A direct conversion of oil harvested from wet algae to biodiesel was undertaken using ethanol at supercritical conditions, eliminating the use of catalyst, feedstock drying and the oil extraction steps. Chlorella vulgaris with 7.3% wt. lipid content was characterised (by elemental, chemical and thermal analyses) and used to assess the supercritical ethanol approach. A biodiesel yield of 47.5% wt. was achieved in a flow reactor at 260°C, 75 bar, aqueous algae concentration of 6 mg·mL-1 and 2 mL·min-1 flowrate. This result demonstrates the advantages of the flow reactor over a batch process where the maximum biodiesel yield was 26% wt. after 6 hours. A life cycle analysis of the proposed route showed that biodiesel yield must exceed 60% wt. to make the process competitive when compared to the traditional route of oil extraction and catalyst transesterification adopted to algae biodiesel production. In comparison to the soybean biodiesel, the use of algae as feedstock would not be justified unless improvements to reduce energy consumption are made.

Energy is an important requirement for population growth, technological progress and urbanisation. Worldwide energy demand has been projected to increase by 5-fold by 2100. Fulfilment of these energy requirements cannot be solely from fossil fuels, such as oil, coal and natural gas, on account of their adverse environmental impacts and concomitant depletion of natural resources. As a result multiple approaches for generating alternative energy are being explored globally. In this study, processed municipal solid waste (MSW) fibre was assessed as a substrate for the production of various bio-energy related products. The MSW was characterised and the results showed that there was, as expected, a wide compositional variation between samples. There was a significant amount of lignocellulosic material found in some samples and the potential to exploit this to generate fermentable sugars was explored. Direct enzyme hydrolysis using 30 FPU (Filter Paper Units)/g Cellic® CTec2 gave a 30 % release of available glucose. Pre-treatments- using hot water, dilute acid and dilute alkali are all applied to enhance sugar release but were all found to be ineffective. The possibility of using MSW as a substrate for cellulase enzyme production via solid state fermentation (SSF) by Trichoderma reesei (T. reesei) and Aspergillus niger (A. niger) was explored. Both fungi grew well on the substrate and following optimization a cellulase activity of 26.10±3.09 FPU/g could be produced using T. reesei at 30 °C with a moisture content of 60 % with inoculation of 0.5 million spores/g and incubation for 168 hr. Addition of extra nitrogen and/or carbon did not improve cellulase accumulation. Acid or alkali pre-treatment of MSW led to reduced cellulase production. Crude enzymes produced from MSW by T. reesei were evaluated for their ability to release glucose from MSW. A cellulose hydrolysis yield of cellulase was 24.7 % achieved, which was close to that obtained using a commercial enzyme. Results demonstrated that MSW could be used as an inexpensive lignocellulosic material for the production of cellulase enzymes. High concentrations of toxic heavy metals were found in all MSW samples tested and this precludes the use of this material as a soil enhancer. Thus studies were undertaken to explore the potential for bioleaching as a means to generate compost that meets environmental standards for safe use. A. niger and Saccharomyces cerevisiae NCYC2592 were used and the impact of growth medium and pH tested. Both organisms were effective at solubilising the heavy metals and this may be related to their ability to synthesise organic acids into the fermentation medium that act as chelators.

Various sago biomass (i.e., sago barks, fibres and wastewater) that potentially converted into value-added products are generated during sago starch extraction process (SSEP). In current industrial practices, such biomass are disposed to the environment and caused severe environmental issues. Therefore, in order to minimise the environmental impacts and to improve economic performance of sago industry, sago biomass is vital to be recovered. On the other hand, a sustainable sago value chain, which involved activities plantation, harvesting, sago starch extraction process (SSEP), and transportations, is synthesised in this thesis via Fuzzy Multi-Footprint Optimisation (FMFO) approach. This proposed approach considered carbon, water, and workplace footprints as well as economic performance of sago value chain. In order to trade-off the conflicts among the optimisation objectives, the concept of fuzzy optimisation is adopted in this approach. Then, recovery of sago biomass in SSEP is focused. In order to prioritise sago biomass for recovery in sago industry, Material Flow Cost Accounting (MFCA)-based prioritisation approach is developed in this thesis. This MFCA-based approach introduced hidden cost (HC) and carry-forward cost (CFC) to determine cost associated with waste streams. Based on the associated cost, waste streams can be prioritised for recovery. Then, this MFCA-based prioritisation approach is further extended as extended MFCA (eMFCA)-based approach to simultaneous synthesise total resource conservation network (RCN) with industrial processes. In this thesis, total water network and SSEP is synthesised simultaneously via eMFCA-based approach. Furthermore, techno-economic and environmental performance of conversion of sago barks and fibres into combined heat and power (CHP) and bioethanol is evaluated. In addition, sensitivity analysis on payback period is conducted in different scenarios due to variation of feedstock cost, enzyme cost, and labour cost. In order to further improve sustainability of sago industry, a conceptual integrated sago-based biorefinery (SBB) is envisaged. Maali’s method is adopted in this thesis to allocate the benefits of each party participating in integrated SBB. Lastly, conclusions and future works are included in the end of this thesis.

The use of biomass derived solid fuels for electricity generation in combustion, gasification and pyrolysis plant has received increasing levels of interest for commercial operation in recent years. However, there are limited tools available which allow a prediction of the performance of these fuels during thermochemical transformation given an understanding of their original chemical structure. As such, this investigation has concentrated on the derivation of a simply utilised classification system able to predict a series of important fuel combustion characteristics given an understanding of both the organic and inorganic chemical and structural composition of any lignocellulosic biomass fuel. A prediction of volatile matter content and char yields during pyrolysis has been made using correlation with aromatic carbon, potassium and calcium contents using both thermogravimetric slow heating and simulated pulverised fuel (PF) entrained flow rapid heating. Alongside this, investigation of the impact of biomass composition, namely aromaticity and alkali/alkaline earth metal concentrations, on char structure and oxidative char reactivity of simulated PF chars has been conducted. Experimental investigation has involved the pre-treatment of a wide range of commercially available biomass fuels including softwood, hardwood, herbaceous and agricultural waste materials to remove both lignin and ion exchangeable mineral species. In addition to this, torrefaction has been utilised to increase the aromatic character of chosen fuels. This has allowed a quantification of the impact of aromaticity and mineral matter concentration on pyrolysis and char combustion reactions to be derived for a wide range of fuel aromaticity and mineral matter contents. Considerable success has been achieved in the classification of an array of lignocellulosic biomass. Accurate prediction of pyrolysis char and volatile matter yields under both slow and rapid entrained flow drop tube heating conditions have been attained using simple empirical correlations with fuel aromatic carbon and alkali/alkaline earth mineral species concentrations (K+Ca being utilised here). This classification system has relied upon the clear linear correlation observed between aromatic carbon content and char yield in the absence of mineral matter influences (R2 of 0.98 and 0.95 being observed for demineralised biomass under slow and rapid heating pyrolysis respectively). In addition to this, the relative enhancement of char yield due to mineral matter interaction with varying concentration of K and Ca within the fuel has been quantified and is used to calculate total char yields. The empirical relationship derived under slow heating takes the following form: Slow Heating Char Yield=(1×Aromatic Carbon )+(16.1 ×(K+Ca) ) Where slow heating char yield is the char yield wt% on a dry ash free basis (daf), aromatic carbon is the wt% daf aromatic carbon content of the biomass and K+Ca is the wt% K+Ca content of the raw fuel on a dry basis. This relationship applies below K+Ca contents of 0.6 wt% db, beyond this a fixed additional char yield of 9.76 wt% daf can be applied as a quantification of the influence of enhanced char yield due to mineral activity as the second term in the above equation. For rapid heating entrained flow pyrolysis the empirical prediction of char yield is conducted as follows: Rapid Heating Char Yield=(0.58×Aromatic Carbon )+(2.43 ×(K+Ca) ) Strong linear correlations of predicted vs. observed char yield have been derived with correlation coefficient R2 = 0.96 and 0.99 with mean relative errors of 7.8 and 8.4% for slow and rapid heating pyrolysis respectively. Furthermore, the influence of biomass aromaticity and active mineral content on char formation processes, the form of chars generated under PF like devolatilisation conditions and their subsequent oxidation reactivity has been studied in detail. Both alkali/alkaline earth mineral matter content (primarily K and Ca) and aromaticity are instrumental in determining the porosity, morphology and surface area of simulated PF chars. Due to its tendency to soften during heat treatment lignin is shown to produce low surface area, non-porous chars under slow heating and this behaviour drives a reduction in char surface area and combustion reactivity with increasing aromatic carbon content. Although char surface areas have been seen to be negatively correlated with increasing potassium and calcium content this may be due to ash blockage of char pore structures. However, the likelihood of a negative impact of mineral enhanced charring has been discussed. K catalysis of combustion reactions is clearly evident in apparent and inherent char reactivities; however, easy quantitative assessment of this influence has been prevented by the clear complexity of mineral behaviour during the pyrolysis process. The development of char structure and reactivity as a function of char combustion degree has also been investigated under entrained flow combustion conditions. The results of this study indicate that by accurately quantifying aromatic carbon, potassium and calcium contents, all lignocellulosic fuels can be classified in terms of their behaviour during pyrolysis (volatile matter and char yields), the form of char structures generated (surface area and porosity) and char combustion reactivity. It is hoped that this relative classification will shed light on the predicted performance of biomass fuels for use in combustion driven power generation infrastructure, especially in pulverised fuel applications.

A biomass-based energy system (BES) is a utility facility which produces cooling, heat and power simultaneously from biomass. By having a BES installed on-site, industrial processes can reduce energy costs by locally producing heat, cooling and power for process and work place requirements. However, several barriers have hindered development of BESs in the energy industry. These barriers include doubts over its operational uncertainties (e.g., seasonal biomass supply, equipment reliability, etc.), the misconception that generating energy from biomass is only a marginal business and the lack of successful cooperative partnerships within the industry. According to literature, such barriers are due to the lack of frameworks that address design aspects and demonstrate the economic viability of a BES. This thesis presents systematic approaches and frameworks to design a BES. These approaches emphasise on integrating synthesis, design and operation decision making for a BES during its preliminary design phase. Firstly, a systematic approach is presented to synthesise a BES considering seasonal variations in biomass supply and energy demand. In this approach, a multi-period optimisation model is formulated to perform technology and design capacity selection by considering seasonal variations in biomass supply and energy demand profiles. This approach is then extended to systematically allocate equipment redundancy within the BES in order to maintain a reliable supply of energy. In this approach, k-out-of-m system modelling and the principles of chance-constrained programming are integrated in a multi-period optimisation model to simultaneously screen technologies based on their respective equipment reliability, capital and operating costs. The model also determines equipment capacities, along with the total number of operating (and stand-by) equipment based on various anticipated scenarios in a computationally efficient manner. Following this, a systematic approach is developed to simultaneously screen, size and allocate redundancy within a BES considering its operational strategies (e.g., following electrical load or following thermal load). Subsequently, a systematic framework on Design Operability Analysis (DOA) is developed to analyse BES designs in instances of failure. This framework provides a stepwise procedure to evaluate proposed BES designs under scenarios of disruption and analyse their true feasible operating range. Knowledge of the feasible operating range enables designers to determine and validate if a BES design is capable of meeting its intended operations. Following this, a systematic Design Retrofit Analysis (DRA) framework is presented to debottleneck and retrofit existing BES designs in cases where energy demands are expected to vary in the future. The presented framework re-evaluates an existing BES design under disruption scenarios and determines its real-time feasible operating range. The real-time feasible operating range will allow designers to determine whether debottlenecking is required. If debottlenecking is required, the framework provides systematic debottlenecking and retrofit guidelines for BES designs. The design of a BES is then extended further to consider its interaction in an eco-industrial park (EIP). Since heat, cooling and power are essentially required in most industrial processes, a BES can be more economically attractive if synthesised for an EIP. As such, an optimisation-based negotiation framework is developed to analyse the potential cost savings allocation between participating plants in an EIP coalition. This framework combines the principles of rational allocation of benefits with the consideration of stability and robustness of an EIP coalition to changes in cost assumptions. Lastly, possible extensions and future opportunities for this research work are highlighted at the end of this thesis.

Achieving a sustainable process system is one of the main focuses in research and development throughout the world. Development in renewable resources is at the peak to replace and reduce the usage of fossil fuel in chemical and energy production. Bio-resources have shown great potential to accomplish a sustainable system, especially bio-waste which also known as biomass, to avoid interruption of food supplement within the supply chain network. However, worldwide implementation of biomass-based process technology is yet to be feasible due to high logistic cost, complexity of biomass properties, fluctuation of biomass availability, and relatively low conversion rate in biomass conversion technologies. Unique regional biomass system further creates research gaps as researches are conducted independently to only focus on specific biomass species available within the region. This raises issue of underutilisation of biomass where biomasses value are not used in the full potential, or ignorance of certain species of biomass (such as food waste, fruit shells and energy crop) in research development. This thesis specifically evaluated the current issues in biomass supply chain network management to enhance the feasibility of biomass industry implementation. The main objective of this thesis is to improve the biomass supply chain network management by integrating underutilised biomasses into existing biomass process plant (built) without major modification on the current process technologies such as equipment redesign or modifications. Underutilised biomasses are referring to those species that yet to have well-developed application (pilot plant scale) or potential biomasses that were ignored in a regional area due to issues such as low availability. This thesis discusses in detail on the relevant previous research works and supporting materials toward the introduction of novel philosophy, element targeting approach, which suggested selection of biomass feedstock via element characteristics instead of biomass species to consider underutilised biomasses into the system. Upon verification of the approach based on literature data and experimental work, element targeting approach is integrated into biomass supply chain optimisation model. The proposed mathematical models enable consideration of underutilised biomasses, and demonstration case studies results have shown promising improvement over the conventional approaches and its capability to handle fluctuation issues in biomass availability.

Biomass combustion has increasingly been used in pulverised fuel coal fired power stations as a way of addressing a wide range of emissions reduction targets. The reuse of existing equipment such as coal mills is essential to minimise the costs of conversion. However the fundamental fracture mechanics involved in biomass comminution are completely different to coal. Thus a thorough knowledge of the comminution properties of all biomass types in coal and biomass mills is necessary in order to minimise operational issues and to optimise milling and combustion. This thesis provides extensive novel characterisation on densified biomass before and after milling. The study analysed 9 densified biomasses, 2 non-densified biomasses, and a sample coal in five different mills; planetary ball mill, Hardgrove Grindability Index testing mill, Bond Work Index ball mill, cutting mill, and a ring-roller mill. Milling was found to have little impact on particle shape, even when an order of magnitude change in particle size was observed. Particle shape is inherent to the particles which comprise a pellet, and is determined by the pre-densified comminution processes. Milling had little impact on compositional particles of herbaceous or wood pellets. Olive cake had the most spherical of all the materials. Thermal pre-treatments of woody biomass not only saw a significant improvement in grindability in all mills, but also enhanced shape factors. The Hardgrove Grindability Index is a poor indicator of the grindability of biomass. The Bond Work Index can be used to analyse the choking potential of biomass pellets prior to full scale mill trials. To optimise milling in coal mills, biomass pellets should be composed of particles close to the required size so that only the pellet comminution stage occurs. The milling behaviour of densified biomass in a laboratory scale ring-roller mill with dynamic classification was investigated for the first time. The milling studies showed that knowledge of a materials critical particle size for comminution through compression is essential to understand its milling behaviour in different mills. The results presented in this thesis not only provide new insight and addresses significant gaps in knowledge, they also provide useful and practical guidance for addressing operational issues such as mill choking, as well as ways to optimise biomass comminution in laboratory and full scale mills, such as mill classifier optimisation based on real particle characteristics.

2\(^n\)\(^d\)-generation bioethanol can be produced from cellulose fraction present in lignocellulosic biomass and has become a significant research focus due to its potential for replacing fossil fuels and decreasing greenhouse gases emissions. In order to produce 2\(^n\)\(^d\)-generation bioethanol, biomass processing is required in order to access cellulose within lignocellulose and convert it into glucose. However, an efficient cost-effective and environmental-friendly process has not been achieved. The aim of this work was to produce glucose from purified cellulose from \(Miscanthus\) \(x\) \(giganteus\), an energy crop. The lignocellulosic biomass was selectively fractionated into its main components, hemicellulose, lignin and cellulose, after extractions using ‘green’ processes in a biorefinery approach. Hydrolysis of the cellulose-enriched fibres into glucose was evaluated using subcritical water (SBW) in a batch reactor at temperatures from 190-320oC, residence times from 0-54min and biomass loading from 0.5-6.4% (w/v). The process used for cellulose purification had significant effect on glucose production by SBW, and higher glucose yields were achieved at higher temperatures and shorter residence times. Glucose was used for bioethanol production. Although the formation of inhibitors during SBW hydrolysis could not be prevented, fermentation could be performed in the presence of these compounds at some conditions, with high ethanol yields.

The rapid depletion of fossil fuel reserves and concurrent increase in global temperatures has resulted in global demand for the production of alternative environmentally friendly fuels. First-generation biofuels that utilise cash crops for the extraction of fermentable sugars currently exist, but are highly controversial due to socioeconomic and environmental reasons such as diverting food production or deforestation. Therefore, second-generation biofuels that utilise lignocellulosic waste materials are a more attractive prospect. In Europe, lignocellulosic biomass wastes such as wheat straw, display great potential for the production of alternative energy sources such as bioethanol for transportation. Conversion to this biofuel requires microorganisms that will effectively utilise the constituent sugars to produce a high yield of product. Saccharomyces cerevisiae (S. cerevisiae) strains possess the most desirable phenotypes for this objective. However, the components of wheat straw are difficult to break down, therefore pretreatment is required. Pretreatment methods vary but often utilise various chemicals that produce compounds that are inhibitory to yeast. This affects the efficiency of fermentations. The focus of this work is on formic acid and a synthetic media containing the main inhibitor compounds released during pre-treatment of steam exploded wheat straw. Six pair-wise F1 crosses between four distinct parental S. cerevisiae clean lineage populations have been generated previously by Cubillos et al., 2009. The 96 F1 progeny from each cross have been assayed for tolerance phenotypes in order to determine QTLs (Quantitative Trait Loci), which will enable us to map genes contributing to the multi-genic trait of inhibitor tolerance. Overall, three QTLs were identified for formic acid and five QTLs were identified from the synthetic inhibitor mix. Candidate genes were selected from the QTL analysis and were tested by performing reciprocal hemizygosity assays to determine which genes are responsible for inhibitor resistance to enable the development of yeast strains suitable for second-generation biofuel production.

The aim of this project is to explore the social and ethical dimensions of the agricultural production of perennial energy crop and crop residues for energy. Biomass – any living or recently living matter – is being promoted in industrialised countries as part of the transition from fossil fuels to an economy based on renewable energy. Various challenges face the use of bioenergy however. One particularly controversial and high profile example has been the use of food crop biofuels in transport which are seen to conflict with food production and to cause significant environmental damage. Suggested ways around these controversies is the production of perennial energy crops such as grasses and trees and crop residues such as straw, which are seen to require fewer inputs and less prime land. Some have analysed the controversies raised by biofuels in terms of controversies around industrial agriculture more broadly: biofuels are perceived to be large scale, monocultural, environmentally damaging and pushed by agri-business and energy interests. This project asks what type of agriculture system perennial energy crops and crop residues are seen as developing within, if at all. This was considered worth exploring because the type of system will have a large bearing on how they are received in future. To this end a theoretical framework of different paradigms of agriculture ranging from industrial agriculture at one end to alternative agriculture at the other was developed and applied to the data. Interviews with key stakeholders and analysis of key documents in the UK and Denmark were carried out to address the question of how perennial energy crops and crop residues are seen as overcoming previous controversies raised by food crop biofuels, in terms of their place in agricultural systems. The thesis argues that stakeholder’s visions of perennial energy crops and crop residues can be understood in terms of four models of agriculture: two industrial and two alternative. These are called “industrialism lite” that involves producing perennial energy crops on marginal land; life sciences integrated agriculture including the biorefinery strategy; multifunctional perennial energy crop production on environmentally marginal land; and ecologically integrated multipurpose biomass production through agroforestry production. There is also an argument which cuts across the paradigms and maintains that regardless of the type of agricultural system used very little or no biomass should be produced for the energy sector because of the scale of resources it requires and the scale of society’s energy use. These positions can be summarised as three different ways to overcome challenges raised by food crop biofuels: further industrialise agriculture; de-industrialise agriculture; and de-industrialise agriculture and reduce society’s energy use, though biomass could still only be used to a very limited extent, if at all, in energy production.

Utilisation of biomass is identified as one of the promising solutions to reduce society’s dependence on fossil fuels and mitigate climate change caused by the exploitation of fossil fuels. By using the concept of biorefinery, biomass can be converted into value-added products such as biofuels, biochemical products and biomaterials in a greener and sustainable way. To enhance the efficiency of biorefinery, the concept of integrated biorefinery which focuses on the integration of various biomass conversion technologies is utilised. To date, various biomass conversion pathways are available to convert biomass into a wide range of products. Due to the substantial amount of potential products and conversion technologies, determining of chemical products and processing routes in an integrated biorefinery have become more challenging. Hence, there is a need for a methodology capable of evaluating the integrated process in order to identify the optimal products as well as the optimal conversion pathways that produce the identified products. This thesis presents a novel approach which integrates process with product design techniques for integrated biorefineries. In the proposed approach, integration between synthesis of integrated biorefinery and computer-aided molecular design (CAMD) techniques is presented. By using CAMD techniques, optimal chemical product in terms of target properties which fulfils the required product needs is designed. On the other hand, in order to identify the conversion pathways that produce the identified optimal chemical product in an integrated biorefinery, chemical reaction pathway map (CRPM) and superstructural mathematical optimisation approach have been utilised. Furthermore, this thesis also presents various chemical product design approaches. In order to solve chemical design problems where multiple product needs are required to be considered and optimised, a novel multi-objective optimisation approach for chemical product design has been presented. By using fuzzy optimisation approach, the developed multi-objective optimisation approach identifies optimal chemical product based on multiple product properties. In addition, fuzzy optimisation approach has been further extended to address chemical product design problems where the accuracy of property prediction model is taken into account. A robust chemical product design approach is developed to design optimal chemical products with consideration of accuracy of property prediction model. Furthermore, together with CAMD techniques and superstructural mathematical optimisation approach, the developed multi-objective optimisation approach has been utilised for the design of mixtures in an integrated biorefinery. For this purpose, a systematic optimisation approach has been developed to identify optimal mixture based on multiple desired product needs as well as the optimal conversion pathways that convert biomass into the optimal mixture. Finally, possible extensions and future opportunities for the realm of the research work have been highlighted in the later part of this thesis.

Pyrolysis is an attractive alternative for the conversion of solid fuels to valuable chemicals and bio-fuels. In order to obtain more H2 and syngas from pyrolysis of coal and biomass, microwave has been adopted to enhance the co-pyrolysis of coal and biomass, which has been investigated systematically in this study. Firstly, conventional pyrolysis of coal and biomass was carried out using a vertical tube furnace. Characterizations of pyrolytic gas, liquid and solid products were conducted to study the different properties of products from the pyrolysis of coal and biomass. More gas products were produced at higher temperatures and biomass samples produced more H2 and syngas than coals. Bio-oils produced from conventional pyrolysis of biomass samples have relatively simpler compositions compared with those produced from conventional pyrolysis of coals. Char samples produced from conventional pyrolysis of coal and biomass samples show different morphologies due to the different nature of original coal and biomass. Secondly, microwave-induced pyrolysis of coal and biomass was carried out and compared with the results of conventional pyrolysis. Microwave-induced pyrolysis was found to produce pyrolytic gas products with higher contents of H2 and syngas than conventional pyrolysis. The bio-oils produced from microwave-induced pyrolysis were not as complicated as those from conventional pyrolysis. The reason for this is believed to be that both microwave irradiation and the longer residence time favour more complete decomposition of large hydrocarbon molecules in coal and biomass, which subsequently results in less complicated composition compared with bio-oil produced via conventional pyrolysis. Char samples from microwave-induced pyrolysis undergo more complete pyrolysis than char samples from conventional pyrolysis, and results in less volatiles remaining. Because of the thermal annealing process by microwave at the later stage of pyrolysis, char samples produced by microwave-induced pyrolysis have higher peak temperatures and burnout temperatures than those produced by conventional pyrolysis. In char samples prepared via microwave-induced pyrolysis of coal and biomass, special structures are found, such as nano-scale fibers in char samples from gumwood and pine, spheres in char samples from coals as well as coal and biomass blends. Based on the analysis of energy balance, it is evident that microwave-induced pyrolysis is a cost-effective and energy saving method for solid fuel conversion.

The increasing concern of energy shortage and environmental pollution attracts worldwide exploration of using sustainable biomaterials for the production of biofuels and biochemicals. Utilising lignocellulosic raw materials for valuable bio-products production is generally considered as a preferred biosynthetic technology. Although various processes have already been proposed, lignocellulose hydrolysis is still remaining as one of the major challenges that prevents wide spread application of lignocellulosic raw materials in biofuel and biochemical production. The aim of this study was to investigate the feasibility of applying soft-rot fungi as a biological pretreatment of wheat straw for the generation of cellulase enzymes and then use the freshly produced enzymes to hydrolyse the fermented wheat straw to a sugar rich hydrolysate. The wheat straw hydrolysate had also been examined for the production of bioethanol and biochemicals, such as succinic acid and itaconic acid. Solid State Fermentations (SSF) of wheat straw were carried out using both Aspergillus niger and Trichoderma reesei. The fermentation conditions, such as moistures content, culture time, addition of nutrients, and modification of wheat straw were optimised for the production of cellulase. In a SSF using autoclaved wheat straw, an enzyme activity of 9.5 FPU/g was achieved. When 0.5% yeast extract and mineral solution were added, the enzyme activities increased to 24.0 FPU/g after 5 days of cultivation. In a SSF of an alkali soaked wheat straw (wheat straw treated with 1% NaOH at 25˚C for 24 hours), 21.8 FPU/g was obtained after just 1-day culture. Optimisation of hydrolysis process led to a hydrolysate containing 59.8 g/L glucose, which was achieved from the hydrolysis of biologically pretreated wheat straw at 18% solid loading, with an enzyme loading rate of 55 FPU/g at 50˚C. Fermentations using the wheat straw hydrolysate resulted in 28.6 g/L ethanol, which was equivalent to 93.4% of theoretic yield. Utilisation of wheat straw hydrolysate for succinic acid production was investigated using recombinant yeast strains. For Saccharomyces cerevisiae D2, the deletion of SDH1 and SDH2 genes enhanced succinic acid production by 68%. Optimisation of fermentation conditions and fermentation scales led to a succinic acid production to around 12 g/L, which was nearly 100-folds of what succinic acid production using the wild S. cerevisiae D2 strain at initial fermentation conditions. Use wheat straw hydrolysate to replace commercial glucose based semi-defined medium resulted in the same succinic acid production yield, but lower concentration due to the low sugar concentration in the hydrolysate. Biosynthesis of itaconic acid using wheat straw hydrolysate was also explored, but no significant itaconic acid production was observed.

This project has investigated the degradation of freshly harvested Willow chips, thermally treated wood pellets and white wood pellets in both indoor and outdoor storage. Novel research has been carried out, by combining a range of fuels, storage scenarios, stockpile sizes and weather/seasonal patterns. A wide spectrum of tests was regularly performed on the stored fuel samples, to determine the extent of chemical, mechanical and biological degradation. The storage trials have been divided into Phase 1 and Phase 2, with Phase 1 starting in April 2011 and Phase 2 in November 2011. The results showed that the extent of chemical degradation was not significant for the different fuels. The main concern for the Willow storage was the high concentration of different fungi on the chips and two pathogenic fungi were identified. In order to fully appreciate the deposition, inhalation and ingestion potential of fungal spores, the release mechanism of the spores from the wood fuels into the air would be recommended as future work. The indoor white wood pellet pile stored in an open barn suffered severe mechanical degradation and it would be therefore advisable to store white wood pellets in a fully enclosed environment with no exposure to ambient temperature and humidity. For the thermally treated pellets, the extent of degradation in the outdoor piles was far more significant than in the indoor one, with rainfall and humidity having an impact on the extent of degradation. Therefore, while the long term storage of thermally treated wood pellets in an open barn with covered storage would be a viable option; pellets stored in outdoor stockpiles would still be vulnerable to mechanical degradation. So outside storage of thermally treated pellets might be an option for short term strategic stocks, but in the majority of cases, covered storage would still be necessary.

Pyrolysis of biomass is a promising and sustainable approach to produce value-added chemicals and biofuels. In order to achieve a high yield of hydrogen-rich syngas from pyrolysis of biomass, the microwave-enhanced pyrolysis of biomass coupled with catalytic reforming was studied systematically in this research. Firstly, microwave-enhanced pyrolysis of biomass was carried out and compared with conventional pyrolysis under the same processing conditions. Characterisations of biomass, pyrolytic char, bio-oil and biogas were conducted to investigate the differences between microwave-enhanced and conventional pyrolysis. It was found that certain types of carbon nano materials were formed on the surface of microwave pyrolytic chars. More biogas was produced via microwave heating, in which the highest H2 content reached 48.2vol.% during the course of microwave-enhanced pyrolysis of bamboo at 800°C. Most of the syngas contents produced from microwave-enhanced pyrolysis of biomass were above 80vol.% at 800°C. Generally, biomass could be converted into biofuel efficiently with microwave-enhanced process. Secondly, in order to increase hydrogen production, microwave-enhanced pyrolysis coupled with catalytic reforming (MPCCR) at 600°C was studied. In catalyst screening, Ni and Fe were applied as active compounds loaded onto different supports such as molecular sieves (13X), Al2O3 and natural minerals. In addition, activated carbon was employed as a reforming agent. It was found that Ni-13X catalyst resulted in a low yield of bio-oil and high yield of biogas around 75wt.%, which was the highest among all the catalysts investigated. It was also observed that activated carbon played a significant role in increasing biogas product and reducing bio-oil yield to less than 1wt.% in both conventional and microwave-enhanced pyrolysis coupled with reforming. MPCCR with Ni-13X and activated carbon enhanced cracking reactions of bio-oil, and subsequently lowed bio-oil yields and narrowed products distribution simultaneously. The maximum H2 content reached 55vol.% by MPCCR of bamboo using activated carbon as the reforming agent. Compared with conventional reforming, there was a sharp increase of H2 yield via microwave-enhanced reforming, resulting in a hydrogen-rich syngas with a high ratio of H2 to CO. Therefore, it is concluded that microwave irradiation enhances the reforming process. Finally, in this study, a novel method for catalyst-free synthesis of multi-walled carbon nanotubes (MWCNTs) from biomass was developed. MWCNTs with a diameter of 50 nm and a wall thickness around 5 nm have been successfully prepared via microwave-enhanced pyrolysis of gumwood at 500 °C. The mechanism for the growth of such carbon nanotubes (CNTs) was proposed as follows: volatiles were released from the biomass and left behind char particles; these char particles then acted as substrates, mineral matter in char particles (originating from biomass) acted as the catalyst, and the volatiles released act as the carbon source gas; the volatiles then underwent thermal and/or catalytic cracking on the surface of char to form amorphous carbon nanospheres; the carbon nanospheres subsequently self-assembled to form multi-walled CNTs under the effects of microwave irradiation. In summary, microwave-enhanced pyrolysis of biomass has the potential to produce high yield of hydrogen-rich syngas not only at high temperatures but also at low temperatures when it is coupled with catalytic reforming processes. It has also been demonstrated that microwave-enhanced pyrolysis of biomass could be used to produce MWCNTs at low temperatures. It can therefore be concluded that microwave-enhanced pyrolysis of biomass is an effective and efficient approach for the conversion of biomass into value-added products under mild conditions.

Concerns about climate change and energy supply security have led to a focus on using biofuels to replace oil-based fuels in the transport sector. Second generation biofuels (SGBs), which are produced from lignocellulosic material such as wheat straw, are currently being developed. This project investigated wheat straw supply for SGB production, focusing on the use of dual-purpose cultivars (DPCs) that are optimised to provide for both food and SGB markets. The project consisted of: agronomic assessment of cultivars and management practices for traits associated with a DPC; economic assessment of the value of these DPCs to farmers and costs of straw delivery; life cycle assessment for quantifying environmental burdens associated with straw production from DPCs; and a farmer survey for quantifying current straw supply and potential future straw supply should a new market for straw emerge. Agronomic trials did not identify any outstanding candidates for use as DPCs from currently grown wheat cultivars or any management practices that would benefit DPC traits. Economic assessment found that straw production costs were lower than the straw price but the overall straw gross margins were much lower than grain gross margins suggesting that grain yield would not be traded off against increased straw yield. Transport costs were slightly lower with the use of DPCs. Environmental burdens for straw production were found to be lower than in other studies but the allocation process had a large influence. From the survey, 50% of respondents were willing to increase straw yields but even with a very generous price of straw, 21% of respondents would not supply additional straw. The work suggests that straw availability is lower than some current estimates and there is only limited scope to increase straw yield through cultivar selection.

The future of biofuel production hinges on a cheap, readily available feedstock. In terms of resources available, lignocellulose is the most abundant renewable resource on the planet, available from a plethora of sources such as agriculture, forestry, industry and municipals, therefore presenting an attractive resource. Cellulose, hemicellulose and lignin are the three main constituents of lignocellulose. The viability of such a feedstock requires as much of these constituents being converted to product as possible and therefore requires the suitable candidate organism to achieve this. Hemicellulose, an often pentose-rich portion of lignocellulose, can constitute as much as 35%. Traditionally yeasts, namely Saccharomyces cerevisiae, have been employed in biofuel production. However, yeasts are often unable to utilise pentose sugars found in the hemicellulose fraction.In this study the ability of Clostridium beijerinckii to utilise the pentose sugars xylose and arabinose was investigated. The ability of C. beijerinckii to utilise these pentose sugars was established, total solvent yields were 0.34 gram/gram (g.g) of arabinose or xylose consumed, in comparison to 0.41 g.g of glucose consumed. The presence of glucose on low mixed-sugar concentrations (1%), but not on high (6%) hindered the use of both pentoses. The ability of C. beijerinckii to utilise pentose sugars in xylan. C. beijerinckii was capable of fermenting xylan and smaller hydrolysate units of xylan, however the solvent yield was poor. The ability of C. beijerinckii to utilise a pentoserich waste stream, spent dried distillers' grains (DDGS) was also investigated. Simultaneous saccharification and fermentation of DDGS produced a total solvent yield of 0.25 g.g in comparison to 0.34 g.g on media containing the equivalent soluble sugars. The ability of C. beijerinckii to utilise both pentose sugars led to in-silico studies to identify gene systems involved and implicated several genes organised in two distinct clusters, one for each pentose sugar, within the genome. Proteomic analyses by liquid chromatography electrospray ionisation tandem mass spectrometry of whole-cell proteins harvested from cultures of C. beijerinckii grown on either xylose or arabinose as the sole carbon source provided further evidence to implicate the gene systems identified by the in silico analyses. Genes were then targeted for characterisation in-vivo using a number of E. coli knock-out mutants, lacking one or more of key genes involved in pentose sugar use. This identified arabinose isomerase, xylose isomerase and xylulokinase genes.

Nearly half the worlds population is dependent on wood as their primary energy source. Therefore with deforestation becoming increasingly prevalent in many regions of the developing world, there is an urgent need to improve combustion efficiency of stoves or to find alternative fuels. Densification of loose biomass residues into briquettes is a means of upgrading the feedstock material. Briquettes are easier to store, more convenient to use and burn at a more steady and controlled rate than loose biomass. This investigation focuses on understanding some of their combustion characteristics and the relationship to the briquette design and manufacture process. The social context of the work is presented through an informal case study considering the potential of briquetting in Ghana. The initial experimental work focuses on developing a process to manufacture newspaper briquettes of consistent quality at low-pressures using a wet technique, and a method to burn them in a controlled way is suggested. These techniques were used to carry out a study on rectangular slab-shaped briquettes, looking at the effect of process variables (density, moisture content and size) on briquette burn-rate. An analytical expression for the normalised burn-rate (NBR) of a briquette in free-air, in terms of these of these variables, was found by numerical fitting. The effect of shape on combustion was also experimentally investigated using cylindrical briquettes with a central hole (holey briquettes) burning in free-air and an analytical expression was derived for their burn rate. The NBR behaviour of sawdust briquettes, rapeseed oil residue briquettes as well as slabs of pine wood was then studied. Rapeseed oil residue has a very different calorific value from that of newspaper, and a method was suggested for predicting the difference in rate as a function of difference in calorific value. In the second phase of the work, a numerical model of pyrolysis was developed. The model assumed that heat transfer through the fuel limited the rate of pyrolysis. The thermal parameters (thermal conductivity, heat capacity and thermal diffusivity) were estimated using a heat probe method, and the kinetic parameters found by numerical optimization. The model was shown to predict, for newspaper briquettes, the experimentally observed size dependent behaviour of the normalised burn rate, and the trend observed for the effect of changes in density. The model was applied to predict the effect of changes in a briquettes thermal parameters on burn rate, and an analytical expression found by numerical fitting. This provides a means of estimating relative changes in burn rate due to changes in fuel properties, and forms the basis for a pyrolysis sub-model for use in stove optimisation. Such a model has the advantage of being able to vary key, easily quantifiable and easily controlled solid biomass briquette properties relative to the behaviour and properties of a well understood fuel such as wood. In the final part of the study, some of the limitations of the numerical model are explored by completing a sensitivity study investigating the relative effect of some of the key assumptions made.

Hydrogen as an energy vector offers great potential for mobile energy generation through fuel cell technology, however this depends on safe, mobile and high density storage of hydrogen. The destabilised multi-component complex hydride system LiBH4 : MgH2 was investigated in order to characterise the destabilisation reactions which enable reduction of operating temperatures for this high capacity system (ca. 9.8 wt.%). In-situ neutron diffraction showed that regardless of stoichiometry similar reaction paths were followed forming LiH and MgB¬2¬ when decomposed under H¬2 and Mg-Li alloys (Mg0.816Li0.184 and Mg0.70Li0.30) when under dynamic vacuum. Hydrogen isotherms of the 0.3LiBH4 : MgH¬2¬ showed a dual plateau behaviour with the lower plateau due to the destabilised LiBH4 reaction. Thermodynamic data calculated from the isotherm results showed a significant reduction in the T(1bar) for LiBH4 to 322 C (cf. 459 C for LiBH4(l)). Cycling behaviour of 0.3LiBH4 : MgH2 system decomposed under both reaction environments showed very fast kinetics on deuteriding at 400C and 100 bar D2, reaching 90 % conversion within 20 minutes. In contrast 2LiBH4 : MgH2 samples had kinetics an order of magnitude slower and after 4 hours conversions <50 %. These results demonstrate the strong influence of stoichiometry in the cycling kinetics compared to decomposition conditions. Investigation of catalysts found dispersion of metal hydrides through long ball-milling times, or dispersion through reaction with metal halide additions provided the greatest degree of kinetic advantage, with pre-milled NbH providing the best kinetic improvement without reducing capacity due to Li-halide formation. Finally, additions of LiAlH4 to the system formed an Al dispersion through the sample during decomposition, which acted both as a catalyst and destabilising agent on the MgH2 component, forming Mg-Al-Li alloys. Decomposition under H2 also showed a destabilisation effect for the LiBH4 component.

Fuel cells could substantially decarbonise domestic energy production, but at what cost? It is known that these micro-CHP systems are expensive but actual price data has been elusive. Economic realities constrain individuals’ decisions to purchase and national policies on climate change, so this lack of understanding has delayed commercialisation and government support. Models were therefore developed to simulate the economic and environmental benefits from operating fuel cell micro-CHP systems in UK homes, and to project current purchase prices into the near future. These models were supplied with economic and performance data from an extensive meta-review of academic and commercial demonstrations; showing for example that fuel cell efficiencies are a third lower when operated in people’s homes rather than in the laboratory. These data inputs were combined with energy consumption data from 259 houses to give a broad definition of operating conditions in the UK. The techno-economic fuel cell simulation model was validated against results from literature and Japanese field trials, and then used to estimate the changes in home energy consumption from operating the four leading fuel cell technologies in the UK. Fuel cells are shown to offer negligible financial benefits in the UK at present. Energy bills would increase in 30-60% of homes, due in part to the low value of exported electricity. Savings are higher in houses with larger energy bills, but significant variation between similar properties confirms that simple trends cannot be used to identify ideal houses for fuel cell micro-CHP. The feed-in tariff proposed by the UK government would radically improve economic outcomes; as 10p paid per kWh of electricity generation would reward fuel cell owners with £600-750 annually. It is estimated that today’s fuel cells produce 360-450g of CO\(_2\) per kWh of electricity generated due to reforming natural gas into hydrogen on-site. Their carbon intensity is therefore 30-45% lower than the UK grid, enabling average annual emissions reductions of 1-2.2 tonnes per home. These reductions depend strongly on the displaced electricity generation method, and could therefore range from around zero when displacing high efficiency gas turbines up to 5.5 tonnes if displacing coal. From learning-by-doing, the price of Japanese 1kW PEMFC systems is shown to have fallen by 19.1-21.4% for each doubling of production volume. Prices are therefore projected to fall from £15,000 today to £6,000 within 10±5 years, determined primarily by the speed and scale of deployment world-wide. A commercially viable price of around £3,000 is however expected to be two decades away, and widely held targets of under £1,000 per kW are argued to be unobtainable with current technologies due to the requirement for extensive balance of plant and auxiliary systems. Combining all these findings, the payback period of PEMFC systems would be 25-45 years with the proposed 10p/kWh feed-in tariff. This could fall to within current system lifetimes after 5-10 years of cost reductions; however, without this level of government support the savings from operation will be unable to give payback without major improvements in technology performance or more favourable energy prices. The carbon cost of current PEMFC systems is estimated at £750-950 per tonne of CO\(_2\) mitigated. This figure is highly sensitive to the carbon intensity of displaced generation, and would reduce to £175/T if generation from coal plants is avoided. Fuel cells are therefore not among the ‘low hanging fruit’ of carbon abatement technologies, although the carbon costs will halve over the next ten years in line with system price reductions. Investment in this technology must therefore be considered a long term strategy for low-carbon energy production.

The optimisations of reduction and operation of Ni-YSZ anode supported micro tubular cells on pure methane were studied. A major problem of SOFCs is nickel anode performance on methane and higher hydrocarbons. The aim of this work was to study the effect of reduction and operation of anode-supported microtubular SOFCs using methane as both reductant and fuel. The results were compared to those from optimised operation using hydrogen. To measure mechanical strength, the three point bending test was employed. Temperature programmed oxidation (TPO) results were investigated to measure the carbon deposition on the anode in order to assess potential damage to the cermet catalyst. Also field emission scanning electron microscope (FE-SEM) and Energy-Dispersive X-ray spectroscopy EDS results were analysed on the anode surface.