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Biofuels obtained from biomass sources have attracted increasing attention due to their economic and environmental benefits. Shifting society's dependence away from gasoline to biofuels is an important contributor to sustainable development and effective management of greenhouse gas emissions. Particular attention has been given to bioethanol as an alternative to gasoline in past few decades. With the limitations of bioethanol as fuel and the sought for better substitutes for gasoline, the focus of this work is geared towards upgrading bioethanol to 1-butanol and iso-butanol whose fuel properties are similar to that of gasoline and, are thus termed "advanced biofuels". Such transformation processes require the employment of suitable catalysts for acceptable productivity and selectivity. Ruthenium complexes have shown great catalytic activity in borrowed hydrogen chemistry which is advantageous to this system. In this study, special interest is given to the design of Ru-catalysts with combined homogeneous and heterogeneous properties in order to preclude the degradation of metal complexes and promote the recoverability and reusability of the catalysts. A two distinct classes of ruthenium-diphosphine has been synthesised and employed in the upgrading of ethanol to advanced biofuels. The first class, ruthenium-PNP with remote functionalities, displayed reasonable activity in the conversion of ethanol to 1-butanol and iso-butanol. With this baseline activity, the heterogenisation of the ruthenium-PNP catalysts was performed and variety of characterisation techniques confirmed the process was successful. The utilisation of the heterogeneous catalysts for ethanol-methanol upgrading to iso-butanol gave moderate yield and selectivity of iso-butanol with good recoverability. The other class of catalysts, ruthenium-PP, showed remarkable activity towards ethanol-methanol upgrading to iso-butanol with good productivity and excellent selectivity.

Solid oxide fuel cells (SOFCs) are highly efficient electrochemical energy conversion devices that can potentially reduce greenhouse gas emissions and revolutionize our energy infrastructures. This research investigates and demonstrates novel and highly efficient methods of utilising renewable biomass-derived gases using SOFC technology with commercially available anode (ASC) and electrolyte supported (ESC) button cells. The utilisation of biohydrogen and biohythane mixtures have been investigated in fuel cell, electrolysis and co-electrolysis modes. Cell electrical performance was characterised using potentiostatic techniques and fuel processing was characterised using online quadrupole mass spectroscopy. Biologically produced mixtures of H2 and CO2 (biohydrogen) from processes such as dark fermentation or photo-fermentation are versatile feedstocks which can potentially be utilised in SOFC devices. In this work, solid oxide electrolysis of biohydrogen has been investigated for the first time and is compared directly with fuel cell mode utilisation in both ASC and ESC supported cells. The effects of fuel variability on SOC overpotentials and outputs have been established and it is shown that cell performance for ESC and ASC is not significantly affected provided the fuel composition stays within 40-60 vol% H2. The effects of fuel variability are affiliated to the presence of the revere water-gas shift (RWGS) reaction, which takes place simultaneously alongside electrochemical processes. The ASC demonstrated better performance in fuel cell mode with more power being produced compared to an ESC, although ASC was more sensitive to fuel variability. QMS measurements indicated H2O and CO production took place in-situ via the RWGS reaction. Electrical power production in fuel cell mode was predominantly through H2 oxidation, whilst CO was converted in the WGS reaction to regenerate CO2 but did not contribute to electrical power production. In electrolysis mode, CO was produced simultaneously through electrochemical CO2 reduction and the RWGS reaction, H2O is electrochemically reduced to regenerate H2. Different operating conditions such as temperature have been studied and shown to have an effect on the performance and outputs of the cell. Co-production of energy and useful chemicals using was demonstrated through investigations into the utilisation of biohythane (CH4/CO2/H2 - 60/30/10 vol%) produced from an optimised two-stage anaerobic digestion (AD) process. The gain in energy yield from two-stage AD was supplemented with additional gains in SOFC efficiency due to the presence of H2 in biohythane, giving up to 77% increased electrical energy yields from biomass overall compared with utilisation of biogas from single-stage AD in SOFCs. The results revealed that biohythane production rather than biogas is a highly advantageous route to energy production from biomass. Furthermore, the effects of fuel variability on the electrical performance and fuel processing of the cell operating on biohythane mixtures at different operating temperatures were studied. When H2/CO2 is blended with CH4 to make biohythane, the SOFC efficiency is significantly increased, high SOFC durability is achieved, and there are considerable savings in CH4 consumption. Enhanced electrical performance was due to the additional presence of H2 and promotion of CH4 dry reforming, the reverse Boudouard and reverse water-gas shift reactions. These processes alleviated carbon deposition and promoted electrochemical oxidation of H2 as the primary power production pathway. Substituting 50 vol% CH4 with 25/75 vol% H2/CO2 was shown to increase cell power output by 81.6% at 0.8 V compared with pure CH4. This corresponded to a 3.4-fold increase in the overall energy conversion efficiency and a 72% decrease in CH4 consumption. A 260 h durability test demonstrated very high cell durability when operating on a typical 60/30/10 vol% CH4/CO2/H2 biohythane mixture under high fuel utilisation due to inhibition of carbon deposition. A significant outcome of this work suggests that decarbonising gas grids by substituting natural gas with renewably produced H2/CO2 mixtures and utilising in SOFC technology gives considerable gains in energy conversion efficiency and carbon emissions savings. Co-electrolysis of biohythane using ASCs was investigated and compared with biohydrogen and biogas (CH4/CO2 60/40 vol%) mixtures, operated with three different co-oxidants (steam, steam/CO2 and CO2). The overall performance and the composition of the output gases have been shown to be very sensitive to the co-oxidant used and by adding H2 to biogas feedstocks improves the overall performance of the cell compared with H2-free biogas.

There is a growing interest in the use of microbial cell factories to produce butanol, an industrial solvent and platform chemical. Biobutanol can also be used as a biofuel and represents a cleaner and more sustainable alternative to the use of conventional fossil fuels. Solventogenic Clostridia are the most popular microorganisms used due to the native expression of butanol synthesis pathways. A major drawback to the wide scale implementation and development of these technologies is the product toxicity of butanol. This study aims to develop a deeper understanding of butanol toxicity at the membrane. Using liposome membrane models and in vitro assays to investigate characteristics such as permeability, fluidity, and diameter, it was found that altering the composition of membranes can convey tolerance to butanol. The effect of butanol on membrane proteins was also investigated, with it causing unfolding of bacteriorhodopsin. The changes to the lipidome of Clostridium saccharoperbutylacetonicum N 1-4 in different butanol environments were investigated with thin layer chromatography and mass spectrometry. In higher butanol concentrations, levels of phosphatidylglycerol and oleic acid had increased significantly. Several metabolic targets were selected for the genetic engineering of Clostridium saccharoperbutylacetonicum N 1-4 (HMT) in an attempt to improve tolerance in butanol. The three targets investigated consisted of two membrane proteins and one enzyme. The first membrane protein, GlpF, a putative butanol channel which appeared to grant a butanol-independent advantage to growth when overexpressed. The second membrane protein, TtgB, is a transporter and overexpression increased cellular growth rate during fermentation. The final protein PssA is involved in lipid synthesis and showed no effect when overexpressed and knockouts appeared to inhibit growth in fermentation. Ultimately, this work highlights the detrimental impact of butanol-membrane interactions, how the cell responds and presents some novels strains, some of which have produced promising results.

This thesis describes the work performed to test and characterise various ion exchange resins as heterogeneous catalysts for the transesterification reaction of tributyrin with methanol to produce methyl butyrate as biodiesel. Depleting reserves of fossil fuel and environmental restrictions on the emission of greenhouses gases have been drawing attention to find a renewable resource such as biodiesel. Biodiesel can be produced via transesterification reaction of oil using an acid or base as a homogenous catalyst. Due to the disposal problem of these catalysts; a more sustainable alternative such as a heterogeneous catalyst is required. Due to the lack of literature on the use of resins as a catalyst, in particular for anionic resins, a preliminary study of the pre-treatment of ion exchange resins was initially carried out to build the foundations for further experiments. Then, a screening test was performed to detect the most promising catalyst. The strong anion exchange resins showed much higher catalytic activity than the strong cation exchange resins. Among the anion exchange resins, Amberlyst 26OH with high density of functional groups and the ability to swell in the reaction mixture gave rise to the conversion of approximately 88 %. The influence of the reaction parameters such as temperature, molar ratio, catalyst loading and stirring rate was investigated by factorial design. The pore size and volume of resins can affect activity for triglyceride transesterification. A proper study of the internal mass transfer on the resins was introduced here. Diffusion Ordered Nuclear Magnetic Resonance Spectroscopy (DOSY NMR) has been utilized for the first time to characterize the internal mass transfer using the motion of the reacting species, confined within their pores. The measurements on the resins failed because of heterogeneity of the samples and the presence of moisture. The results of these resins were compared with mesoporous silica SBA-15, which allowed simple characterisation. Tributyrin and methyl butyrate showed reduced diffusion coefficients within the confined pores. At the same time, glycerol exhibited interesting behaviour; it showed enhancement of its diffusion coefficient due to the ability of the silica support to disrupt the intermolecular H-bonding network of glycerol. Ion exchange resins are high-performance catalysts and catalytically active even at very low temperature. The work reported here enhance the use of ion exchange resins more used in catalysis, and the choice of resin-type could be aided by the comprehensive characterisation provided here.

Miscanthus is a promising dedicated biomass crop for the bio-industry. The genus includes 16 species and recently interspecific hybrids of Miscanthus with increased biomass yield have been created. However, our ability to use Miscanthus biomass for producing energy and chemicals sustainably and profitably depends on the ability to cultivate it on marginal lands and harnessing its cell wall recalcitrance. Although cell wall characteristics vary between genotypes, the full range of this variability in the genus has not been fully explored yet. We selected 49 Miscanthus genotypes, from 10 different genetic groups, according to the climate and soil conditions of their area of origin to investigate the extent of variability of cell wall characteristics across the Miscanthus genus. We know that, besides genotypic variation, cell wall properties are also affected by abiotic stresses. However, there is little information about how nutrient limitation, typical in marginal lands, affects the cell wall composition of different Miscanthus species and their hybrids. To address this, we selected 12 genotypes from the beforementioned group, with contrasting cell wall structure and quality for conversion, and imposed a nitrogen and phosphorous limitation during their growth for 60 days. The recalcitrance of cell wall to deconstruction was affected by the organ in a species specific manner. In general leaf material showed a lower recalcitrance to enzymatic deconstruction. Stem material compared to the leaf material had a higher xylan decoration, a lower ratio between cellulose and hemicellulose and a higher ratio between syringyl and guaiacyl monomers in the lignin. Under nitrogen and phosphorus limitation, there was a species-specific alteration of the saccharification efficiency and the carbohydrate profile of the cell wall. The outcomes of this work increased our knowledge about cell wall composition in the genus Miscanthus and the effect of specific nutrient stress on cell wall composition and recalcitrance. A future for the Miscanthus biomass crop can be envisioned where specific nutrient limitation can be used as a treatment to direct the quality of the biomass for conversion.

Current Polymer Bonded Explosive (PBX) formulation is limited by a compromise - optimised final properties against processability. While solid loading (explosive content) would ideally be maximised and plasticiser content would ideally be minimised, this would make the formulation too viscous to cast into its casing and require long and arduous mixing processes using conventional techniques. However, with Resonant Acoustic Mixing (RAM), PBX formulation does not have to be constrained. Instead of traditional mixing blades, mixing is achieved by the use of a vibrating platform to impart acoustic pressure waves (vibrations) into the mixture, agitating it. The added ability to mix in the end use casing (mixing 'in-situ') also renders casting obsolete in many scenarios. In order to maximise the benefits of RAM with regards to next generation formulation-optimised PBX manufacture ('PBneXt'), the underlying mechanisms of how the technique works, how efficiency (time and energy required for homogeneity) can be determined and maximised, and how final material properties may change between casting and 'in-situ' processing methods, must be better understood. The research aim of the PhD is therefore to assess how mixing efficiency of RAM can be measured and optimised to maximise its benefits, with a focus on how aspects of machine control and mixing vessel design can be altered to improve the mixing mechanisms on which the technique relies. Areas investigated experimentally include the effects of acceleration and mixer intensity (linked to power draw) setting, mixer model and unit, vessel material (with regards to surface free energy and thermal properties), and vessel surface finish (with regards to roughness). It is found that by modifying these variables, the time and energy required for mixing can be substantially reduced. A comparison between material properties of composites mixed 'in-situ' and 'mixed and cast' is also undertaken. The findings are then reconciled with wider literature observations and recommendations are made as how to best implement RAM for 'PBneXt' manufacture, ultimately allowing for explosive compositions with improved performance, mechanical, safety, and ageing properties.

With increasing concern of environmental pollution and carbon emissions, energy production with renewable feedstocks especially biomass was become more attractive in recent decades. Liquid fuel, which was also called bio-oil, can be directly produced from biomass through fast pyrolysis. Nevertheless, the quality of the bio-oil generated from fast pyrolysis is low due to high oxygen and water content, low heating value and high viscosity. Therefore, upgrading of bio-oil is essential for its full utilization as a kind of renewable energy. This work is aimed to study an innovative method for the bio-oil upgrading without external hydrogen that hydrogenating a bio-oil model compound with in-situ hydrogen generated from aqueous phase reforming of glycerol. The process was studied using guaiacol as the model compound of bio-oil and conducted in a batch stirred reactor. Initially, experiments of hydrogen production from glycerol reforming were performed at different operation conditions to maximize hydrogen yield. Then experiments were conducted to study hydrogenation of guaiacol with in-situ produced hydrogen from glycerol. The effect of the primary process variables was studied, and a potential reaction pathway was proposed followed by a catalysts screening in this process as a collaboration with Boreskov Institute of Catalysis (Novosibirsk, Russia). For the experiments of glycerol reforming, it was found that the operating conditions had great influence on the hydrogen yield and selectivity of gas product. Optimum conditions were determined where the maximum hydrogen yield was obtained. In the experiments of hydrogenation of guaiacol, it was notable that hydrogenated aromatic compounds were formed in the absence of glycerol. It is believed that methanol produced from hydrolysis of guaiacol is the internal source of hydrogen. In addition, it was observed that guaiacol conversion and yield of organic soluble product increased with additional glycerol. Moreover, Ni/Al2O3 showed a better performance than promoted Ni based catalysts in terms of guaiacol conversion and organic soluble product yield. It is predicted that the capacity of hydrogen production of Ni based catalysts was inhibited by promotors.

The production of biofuels from pyrolysis of biomass is one of the alternatives to fossil fuels, but the high oxygen content, acidity and instability of the pyrolysis bio-oils still represent a challenge limiting its widespread diffusion. The aim of this research project focuses on develop further an existing technology to stabilise the pyrolytic oil by hydrogenation reaction and in evaluating the economic feasibility for industrial development. Based on literature review, new catalysts have been synthesised and tested for the bio-oil hydrogenation. By impregnation technique, the zirconia has been doped with Pd and not noble metals (Cu and Fe), characterised and their performances studied, in term of conversion and selectivity for key bio-compounds. Vanillin was completely converted after 80 min at 100°C and 50 bar, in presence of PdFe/ZrO2. Furthermore, promising results were obtained testing the PdFe/ZrO2 catalyst on a real water bio-oil fraction, where the catalyst was able to maintain ~90% of carbon in the liquid phase, reduce the polymerisation degree and the acidity of the bio-oil under mild conditions. With the idea to minimise the hydrogen consumption and lowering the energy demand for the hydrogenation, the reaction was carried out at low operating conditions using a membrane reactor. A Ru-polyethersulfone (PES) catalytic membrane was synthesised and tested for furfural hydrogenation achieving a TOF equal to 48,000 h-1 , at 70 ºC and 7 bar, but metal leaching with consequent deactivation was noticed To address the deactivation of the Ru-PES membrane, Ra u- Polyether ether ketone (PEEK -WC) membrane was developed using a green solvent and tested with a simulated water bio-oil fraction at different temperature (65-85°C), pressure (11-18 bar) and H2 flow rate (5 -25 mL/min.). The PEEK-WC membrane resulted in an enhanced stability and good hydrogenation activity. Finally, to enhance the understanding of the real feasibility at industrial level of the proposed biorefinery pathway (Pyrolysis/HDO), an economic feasibility study was designed and carried out for two different scenarios: (i) using micro algae as feedstock for producing drop-in bio-fuels, which resulted in a minimum fuel selling price of 1.418 $/L, ~ 50 % higher than fossil fuels; and (ii) pinewood bio-oil (current feedstock) orientate to for producing chemicals (for 75% of bio oil processed) and fuels achieving an economic potential of 38,234 MM$/y for 10Mt/y feedstock treated, suggestion a valid alternative for green chemicals production, with relative price decrement.

The increase of global carbon emissions by 2.7% in 2018 from the 2015 level indicates that the utilisation of fossil fuel, particularly coal, as the primary energy source is still very significant worldwide. Many countries have made efforts to reduce their carbon emissions by replacing coal with biomass. The UK government has promoted the gradual transition from coal-firing to biomass-firing to achieve complete coal power plant shutdown by 2025. This transition program is also supported with several incentive schemes to encourage the current and planned future coal-firing power plants to utilise biomass. However, several disadvantages are attributed to the utilisation of biomass as an energy source. Significant exploitation of woody biomass contributes to flooding, increasing carbon debts, and food security issues due to deforestation. Additionally, the use of herbaceous biomass causes operational problems in power plants due to severe ash deposition and corrosion. Treated wood is abundantly available and is known to complement virgin biomass in combustion to mitigate the disadvantages associated with woody and herbaceous biomass combustion. In the EU, 52.9 million tonnes of waste wood is produced annually, 54% of which is utilised to produce electricity. However, treated wood contains trace elements (TE), e.g. arsenic, cadmium, copper, lead, nickel, etc. sourced from prior anthropogenic treatment, e.g. preservatives and paints. These elements are relatively volatile at high temperatures and are released to the atmosphere during combustion. Ingestion of these elements may harm human metabolism and pose other health risks to wildlife. This thesis aims to develop a comprehensive model to predict the fate and the occurrence of trace elements (TEs) and ash-forming elements (AFEs) in combustion of treated wood and virgin wood. The combustion process considered is based on the biomass combustion operation in the 250-kW entrained-flow boiler in the UKCCSRC Pilot-scale Advanced Capture Technology (PACT) facility in Sheffield, UK. The developed model is designed to predict the downstream concentrations, the fate profiles, and the occurrence profiles each AFE and TE. The modelled downstream concentrations as the element concentrations in uncooled downstream gas are well validated by the experimental downstream concentrations measured with the online inductively-coupled plasma - mass spectrometer (ICP-MS). The modelled fate and occurrence profiles of each AFE and TE are in good agreement with the experimental results pertaining to the respective elements.

The development of sustainable bioenergy plays an active role in the decarbonisation of the energy sector. Unlike other renewables, bioenergy has the potential to expand its applications beyond climate change mitigation by providing complementary environmental and socio-economic benefits that support the Sustainable Development Goals. The deployment of bioenergy could be particularly beneficial in the rural areas of many low and middle-income countries where traditional uses of biomass still prevail. Locally available biomass in rural areas, such as agricultural residues, could be harnessed in more efficient and sustainable manners, and this could be promoted with bioenergy development. The roll-out of these technologies also arises challenges across the environmental, economic and social dimensions, especially for emergent technologies. Tackling these challenges requires a wider understanding of bioenergy technologies' impacts across these dimensions, and this could be achieved through comprehensive and integrated assessments that investigate these dimensions. This research, therefore, seeks to gain further knowledge to unfold the following questions; how bioenergy technologies using agri-residues could be sustainably and feasibly deployed?, and what are the wider co-benefits, from a sustainable development perspective to rural communities and agro-industries?. This study aimed to evaluate the feasibility of small-scale gasification systems to generate power and heat, using indigenous agricultural residues, to meet the energy demand of rural areas. Considering also that bioenergy is set within local contexts, this research was framed in a case study on the coffee sector in Colombia, using coffee stems as feedstock. The methodology in this research consisted of a combination of multidisciplinary approaches, comprising process modelling for a technical assessment, lifecycle assessment (LCA) and techno-economic analysis. The results of the technical assessment indicate that the gasification of coffee stems could generate a fuel gas suitable for power generation in engines. In addition, the heat recovery and integration to supply the demand for coffee processing could enhance the conversion efficiency of the system. The LCA results show that deploying the coffee stems gasification-CHP system could impact positively on many environmental issues, including climate change, when traditional biomass uses and energy production using fossil fuels are replaced. However, trade-offs should be considered for certain scenarios, such as those replacing grid electricity with high-hydropower generation. The evaluation of the economic feasibility indicates that costs of power generation in the gasification systems could equalise the costs of Diesel-power generation when the system reaches high capacity factors. Matching the grid-electricity tariffs is more difficult to attain even at high capacity factors. The integration of the heat vector in the coffee processing chain contributes to fuel savings and could be translated into a heat credit that reduces the power generation costs. The key findings from this research were integrated under a multidimensional framework that prompted discussions on pivotal drivers, synergies and trade-offs of this bioenergy system. The synergies relate to the importance of balancing the biomass availability and the energy demand in context-specific agricultural sectors. It also emphasises the usefulness of harnessing the biomass conversion by implementing heat recovery pathways in the system, and of maximising the utilisation of the system (increasing the capacity factor) to enhance the systems feasibility. The framework also contributes to understanding how bioenergy from agricultural residues could contribute achieving the Sustainable Development Goals. The multidimensional framework highlights potential co-benefits to rural communities, in relation to improving energy access and health, promoting sustainable agriculture and economic growth, and reducing inequalities in rural areas. In conclusion, this research supports the overarching argument that bioenergy technologies have the potential to deliver energy demands in rural areas while tapping the potential of agricultural residues. Overcoming barriers to these systems deployment is still challenging. Yet, the synergies identified across all the dimensions could help to attain the system's feasibility and sustainability. Furthermore, wider societal co-benefits to rural communities could also be realised, as suggests the strong correlation between bioenergy and the Sustainable Development Goals.

Biomass pyrolysis is one of the most promising renewable energy technologies. This research aims to create a model which automatically designs a biomass slow pyrolysis reactor from the user inputs and provides mechanical specifications, kinetic properties and process parameters. From literature, the rotary kiln was identified as the most promising slow pyrolysis technology. This research divides the complex reactor design into three main parts, related to the transformation of the feedstock into the product: bed of solids, heat transfer and kinetics. The three aspects were integrated, and the reactor divided into physically identical slices for more straightforward implementation and to overcome model divergences. - The bed of solids defines and describes the behaviour of the solids inside the reactor mathematically. The length of the reactor must be calculated, and the contact areas to transfer heat from the wall (heat source). - Heat transfer is critical within pyrolysis. The model must ensure that all the particles reach the target temperature. The heat is indirectly transmitted to the solids and gases through conduction, convection and radiation. - Pyrolysis kinetics are challenging due to the complex mixture of substances in the feedstock and products. Isoconversional methods are used to estimate the value of the pre-exponential factor and activation energy for the conversion of each feedstock into the products. Additionally, the reaction orders are optimised through an innovative method that compares the error between different values. The result is a thorough methodology and comprehensive model for the design of a rotary kiln. This methodology included assumptions to achieve a compromise between accuracy, computational time and power. The finished model allows users to investigate custom reactor designs, as they can specify key variables such as feedstock and scale. It is a very powerful tool that can be used in industry or by potential investors to obtain a first approximation of the dimensions of a pyrolysis reactor. For research, it provides a robust methodology for the design of slow pyrolysis rotary kilns. It is acknowledged that the reactor model is not perfect, and some parts could be improved, but it provides a valuable step forward in the development of slow pyrolysis reactor design.

Valorization of lignin biomass for the sustainable production of high-value chemicals and materials is a key aspect of a nascent global bioeconomy. Challenges in the whole cell bioprocess of this abundant feedstock include its depolymerisation associated with the uptake of the monomeric substrates and biotransformation into valuable products. Whole cell biosensors permit real time intracellular detection and measurement of metabolites allowing for high-throughput screening, evolution and metabolic pathway optimisation applications. Therefore, they are potential biotechnological tools to enable the biosynthetic conversion of lignin biomass feedstocks into value-added products. This thesis presents the development, characterisation and optimisation of transcription factor-based whole cell biosensors for key aromatic substrates and products in the lignin valorization bioprocessing. Firstly, the ferulic acid (FA) biosensor system was developed for the detection of major aromatic chemicals derived from lignin biomass, including ferulic acid. Then, it was employed for the screening of enzymatic degradation of complex biomass sources. Secondly, the protocatechuic acid (PCA) biosensor was developed for detection of protocatechuic acid, a central intermediate in the microorganism-based biocatalysis of lignin. This biosensor was employed for the directed evolution of its transcription factor component PcaV aiming to alter its substrate specificity for sensing of new effectors. The evolution method led to the generation of the Van2 biosensor for detection of aromatic aldehydes, including vanillin. This biosensor was characterised biochemically and structurally. Moreover, the role of the amino acid substitutions that led to vanillin sensing were assessed in vivo. Furthermore, the FA and PCA biosensors were optimised employing a Design of Experiment methodology for dose response curve tuning. Finally, the FA biosensor was applied to demonstrate two biosensor-based strategies to overcome membrane transportation challenges in a lignin whole cell bioprocessing concept. Overall, biosensor systems were developed to permit the detection of key molecules in different stages of the biological valorization of lignin, including the degradation, biocatalysis and final product. They will provide new tools and applications to expedite the biological lignin valorization.

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.

The compositions of explosives over the years have evolved as terrorists find new and creative ways to fabricate what are termed homemade, or improvised, explosive devices. As a result, routine methods used by defence and security laboratories for the targeted screening and identification of explosives and related compounds in casework samples become no longer appropriate. Solid phase extraction (SPE) for sample clean-up and target analyte preconcentration, followed by liquid chromatography-mass spectrometry (LC-MS) for separation and detection, is typically the method of choice for detecting trace organic explosives in complex sample types. The ‘matrix effect’ phenomenon, however, remains problematic and can lead to false negatives and even miscarriages of justice. A potential solution lies in a more effective sample preparation procedure. The aim of this work was to develop a novel SPE method, based on the principles of both selective extraction and exclusion, and combine it with 3D printing technology and high accuracy analysis, in order to provide a miniaturised, flexible solution to matrix effects in the analysis of organic explosives. In general, the established sample-dependent, dual-sorbent SPE procedures with existing commercial equipment provided the desired overall reduction in matrix effects, as well as increased selectivity and sensitivity, in the trace analysis of organic explosives from complex samples. The adaptation of multi-sorbent SPE to a 3D-printed version achieved performance metrics comparable with conventional SPE cartridges, as well as additional advantages including: (a) greater flexibility to be packed with the amount and sorbent chemistry of choice by the user, (b) potential to multiplex and modify parts to generate tailored arrays for a particular sample type, with no additional tubing or connecting parts, (c) low-cost and easy accessibility for laboratories, (d) on-demand nature, enabling rapid production of parts, as required, with no ordering delay, (e) low carbon footprint from removal of the requirement for delivery, (f) easy connection with syringes for on-site use, (g) good stability in a broad range of common organic solvents, which could allow application to extraction in other scientific fields, and (h) ability to both preserve the sample and speed up the overall analytical process chain. Furthermore, the successful application of the novel 3D-printed SPE approaches to real and simulated forensic scenarios proved its fitness for purpose. In particular, this approach provided increased assurance through enhanced removal of matrix and, ultimately, showed great promise for the compatible exploitation of additive manufacturing technology in sample preparation and, more generally, analytical chemistry.

Compared with conventional fossil fuels, biomass has its unique advantages in terms of wide availability, potential high energy generation and carbon neutrality. Up to now, biomass combustion has made huge contributions to meet the heating demands of both commercial and domestic fields. However, one of the main challenges of biomass combustion is its pollution emissions, including NOx, CO and hydrocarbons. Meanwhile, the release of CO2 from biomass combustion which contributes to the greenhouse effect, should be paid more attention as well. The present PhD study aims to explore the combustion behaviours of biomass fuels by burning individual biomass pellets under different combustion atmospheres (air and oxy-fuel) and develop catalytic methods of NOx emission abatement for the potential use in small-scale and domestic biomass boilers. In this study, five different types of biomass (wood, straw, miscanthus, peanut and torrefied wood) pellets were applied as the fuels in a visible drop tube furnace (V-DTF) to investigate the combustion behaviours under both conventional air and oxy-fuel (O2 fraction of 21%, 25% and 30%) combustion atmospheres. Four combustion phases, namely pre-heating, volatile combustion, volatile/ char overlap combustion and char combustion were observed and identified. As expected, a shorter total burnout time of a biomass pellet was observed when increasing the combustion temperature (from 800°C to 900°C), which was mainly contributed more rapid char combustion. Increasing oxygen fraction from 21% to 30% also accelerated the pellet combustion, shortening the total burnout time in oxy-fuel atmospheres while the total burnout time under conventional air combustion condition was between those of 21% O2-79% CO2 and 25%O2-75% CO2 atmospheres for untreated (raw) biomass fuels. Due to the impacts of C-CO2 gasification reaction and torrefaction, torrefied wood was observed to have shorter char burning time under 21% O2-79% CO2, hence resulting in shorter total burning time than the air combustion. By means of high-speed camera and MATLAB software processing the flame images, the volatile flame brightness was found to increase with O2 fraction in oxy-fuel atmospheres while the brightness of volatile flame in air was close to the one in 30% O2-70% CO2 atmosphere. The tests to investigate the combustion performance and gaseous emissions (e.g. NOx, CO and CH4) were carried out in a domestic 50kW biomass boiler with different primary and secondary air settings by using typical wood pellets. The results showed that the boiler had good performance in terms of NOx emissions under all conditions. Continuously fluctuating CH4 and CO were detected in the combustion chamber during normal combustion processes due to insufficient mixing and limited chamber space. More importantly, both CH4 and CO concentrations followed the same variation trend. The generation of CH4 and CO was found to be determined by the amount of primary air while that of NOx was more dependent on the nitrogen content of the fuel. Both CH4 and CO can potentially be utilized to reduce NOx emissions in suitable SCR processes. Performance of CH4-SCR and catalytic NOx-CO reactions were experimentally tested in a lab-scale fixed bed reactor with simulated flue gas atmospheres. For CH4-SCR tests, Co-ZSM-5 displayed great activity to reduce NOx with the help of excess oxygen. The optimum NOx conversion rate reached over 60% when using 2.89% or 4.89% Co-ZSM-5 (Si/Al ratio of 12.5) under the furnace setting temperature of 400°C. The catalytic performance of NOx reduction over Co-ZSM-5 was suppressed significantly in the absence of oxygen although there was activity between NOx and CH4 at high temperatures due to thermal reactions. Fe-supported catalyst was inactive in CH4-SCR system, but it could promote catalytic NOx-CO reactions in the absence of oxygen (with the maximum NOx reduction of 92.62% @ 500°C). However, the catalyst lost its activity when there was O2 in the feed gas.

Biomass is an excellent renewable energy source for alleviating the energy crisis and reducing the GHG emissions from the combustion of fossil fuels. Since the microalgae can accumulate lipids in the cell, the concept of using algal biomass for biodiesel production has attracted significant attention in recent years. The advantages of using microalgae as a biofuel source are that these organisms have a high growth rate, high lipid content and low requirement for nutrition compared to oil-producing plants. The most important property is that they can absorb CO2 from the atmosphere thus contributing to an overall reduction of GHG emissions. The existing downstream processes of biodiesel production are complex and costly, which makes the product not compatible with other bioenergy sources. Therefore, it is important to develop alternative routes of utilising algal biomass for energy production. This study mainly developed a novel method to deliver algal biomass through the air intake into a diesel engine for energy production and evaluated the environmental impact of the processes. A correlation between engine work produced during aspiration and combustion of algae biomass suspension was found. At constant flowrate and greater than 5% of biomass concentrations, a contribution to energy release during combustion from the aspirated algae could be observed. However, the aspiration of low concentration biomass suspension produced a negative impact on engine performance relative to water-only aspiration. From the perspective of the impact on the environment, the increase of biomass concentration and aspiration flowrates in the life cycle impact assessment of the whole process show a proportional increase in GWP, NOx and water consumption. Contribution analysis indicates that changing the biomass concentration has a greater impact on the environment than changing the aspiration flowrate and the proportion of total impact of the DSP steps increase with the increase of biomass concentration. Moreover, as an alternative way of using algae/diesel emulsion for energy generation, the results of the investigation on stability and viscosity of algae/diesel emulsion show the maximum stable time is 8.5 hours with the relative low viscosity of 49.9 mPa·s. However, the engine test of the stable emulsion was not successful due to the injector failure caused by phase separation of the emulsion under high pressure in the modern diesel engine. Overall, these findings demonstrate the feasibility of utilising the energy content of algal biomass in combustion without lipid extraction, with added benefits of reducing NOx emissions. It therefore gives a foundation for further exploration and development of algal biomass-derived bioenergy production.

Microalgae biomass is attracting increasing attention worldwide as a promising feedstock to develop multipurpose third generation biorefineries. Due to its ability to accumulate lipids for biofuel production, along their capacity to synthesize natural polyphenolic antioxidants for fine chemical and pharmaceutical applications, microalgae biomass is an excellent resource for production of bioenergy and high-value compounds. However, efficient downstream processes to recover target biomolecules from microalgae remains a major bottleneck. Conventional extraction techniques for biomolecule extraction from microalgae rely on the use of petroleum-derived volatile organic solvents, which are being increasingly restricted in the chemical industry due to their adverse effects on environment and human health. Consequently, cost-effective technologies to extract biomolecules using alternative solvents with a better environmental, health and safety profile are required. Therefore, the main objective of the present thesis project is to evaluate green solvents for extraction of lipids and polyphenols from microalgae for sustainable production of biodiesel and bioactive antioxidants. Microalgal lipid extraction was performed using a variety of bio-based solvents, while antioxidant recovery was accomplished using renewable deep eutectic solvents and compared against benchmark organic solvents. Lipid extraction performance was evaluated in terms of lipid extraction capacity, saponifiablity and biodiesel yield after transesterification; meanwhile, antioxidants recovery performance was assessed based on total phenolic content, antioxidant activity and polyphenolic profile of the extracts. Additionally, extraction solvent effects on biomass structure were assessed to enhance further bioprocessing steps. Lastly, the feasibility of different integrated strategies for co-production of biofuel and antioxidants from microalgae were explored to maximize the quantity and quality of the biorefinery output. Overall, this research project provides a comprehensive evaluation of advanced microalgal biorefineries for sustainable production of biofuel and valuable chemicals, contributing to promote strong bio-based industries for transitioning to bio-based economy.

In this thesis, we explore the formation of char during lignin pyrolysis. This is accomplished using computational chemistry to study the energetics and mechanisms of reactions involved in lignin char formation. In Chapter 1, the background for the project is given, highlighting the global climate and energy crises, as well as providing an overview of biomass, biofuels, and biomass thermochemical conversion techniques. Lastly, the research gap is outlined and the key research topic of the thesis is introduced. In Chapter 2, we assess the stability of a range of lignin derived phenolic bio-oil compounds through the calculation of bond dissociation enthalpies. Here we show that methoxy functional groups exhibit much lower bond dissociation enthalpies than other groups found in lignin derived phenolic compounds which is in agreement with literature reports of their scarcity at higher pyrolysis temperatures. Conversely, unsaturated functionalities exhibit high resistance to homolytic cleavage and are more thermally stable. In Chapter 3, we propose a reaction mechanism for the formation of aromatic char clusters from the products of lignin decomposition. Here, through investigation of sixteen parallel pathways, we show clearly how unsaturated lignin derived monomers may concatenate through cycloaddition reactions and subsequently aromatise through elimination reactions to yield polycyclic char clusters. Chapter 4 is concerned with the aggregation of these char clusters through a continuation of the reactions reported in the previous chapter. By employing the Same Level Different Basis approach, the growth of condensed char clusters up to eleven rings is modelled and the impact of cluster size on reaction barriers is assessed. Chapter 5 contains concluding remarks that draw upon the results reported in Chapters 2-4. This chapter also proposes new avenues for the investigation of lignin char formation and the potential impact of the work contained herein to other closely related fields.

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.

Oxides of nitrogen (NOx) are gases that can cause harm to flora, fauna and human health. NOx emissions can result in acid rain, act as a nucleus to form particulate matter (PM) and have been known to cause respiratory disorders in humans. Recent regulations to curtail the emissions of NOx (and other emissions) have been implemented globally. The current legislation, the Industrial Emissions Directive (IED) has set ever more stringent limits for NOx from existing power stations across the European Union (EU). To meet these targets, power stations operating with pulverised fuels will be required to use multiple reduction technologies. This research is focused on using by-products of biomass combustion, pulverised fly ash (PFA) and furnace bottom ash (FBA) in co-combustion with coal to reduce NOx in fuel flexible power stations. The increase in K, Ca, Na and Mg in the fuel blends may provide catalysts to promote a reduction mechanism for NOx to diatomic nitrogen during combustion. Three bituminous coals, representative of those used for power production were selected for co-combustion with the two ash additives. To compliment the research, a low reactivity coal was also examined under the same conditions. A high reactivity biomass was also examined using coal PFA as an additive, with relatively high Fe. The experimental work investigated the nitrogen partitioning and carbon conversion of the fuel blends through a variety of conditions; Low heating rate (LHR) and high heating rate (HHR) analysis was carried out. The range of experimental work revealed, through the addition of the FBA and PFA to all of the coals, volatile nitrogen was increased and char nitrogen reduced. Carbon conversion was also increased across all of the coals. The addition of the coal PFA to the biomass also realised the same trends in volatile nitrogen and carbon conversion. These are favourable conditions in a large-scale furnace fitted with Low-NOx technology. A slice model was used to represent of a well stirred pulverised fuel furnace. By dividing the furnace into several 3-dimentional slices the model can calculate the overall performance of a furnace. The slice model can be used for the prediction of NOx emissions from a furnace based on the fuel properties, and furnace operating conditions. When the adapted model was applied to the bituminous coals with and without the additives, accuracies within 10% of experimental work were achieved. The use of PFA and FBA may present a cost-effective NOx reduction technique when combined with other low NOx technologies in fuel flexible power stations.

Anthropogenic fossil fuel CO2 (f f CO2) emissions are an important topic of research as they increase atmosphericCO2 which affects the global greenhouse gas budget and radiative forcing of the Earth’s climate. The challenge with investigation of atmospheric CO2 mole fraction variation is the difficulty of separating biogenic and anthropogenic sources. Radiocarbon dioxide (14CO2) observations provide a method for separating fossil fuel emissions from other sources. This is because fossil fuels, having been buried under ground for millennia, do not contain 14C; which has a half life of 5730 years. Therefore, 14C can be used as a tracer of anthropogenic activity. When combined with models of atmospheric transport, 14CO2 measurements could be used to determine the magnitude of the UK’s fossil fuel CO2 emissions. Previous 14CO2 measurements in the UK, as part of the Greenhouse GAs UK and Global Emissions (GAUGE) project, have shown that it is difficult to use 14CO2 to quantify UK f f CO2 emissions. The reasons for this were: (1) Only a limited number of samples under low f f CO2 mole fraction conditions were taken; (2) The abundance of nuclear power stations in the UK that release 14CO2 emissions means a correction must be applied to the measurements. Flask samples are most commonly taken over the period of minutes providing only a snap shot of the atmospheric gas composition, these are then compared to models which are on the time frame of hours. To make the samples collected more representative and comparable to the models an integrated sampling system was designed and tested that is capable of collecting samples representative of hours. The next stage in the sample analysis is the extraction of the CO2 from the whole air sample. Traditionally, this has been achieved cryogenically using liquid nitrogen. An extraction line similar to those utilised at other laboratories was constructed and tested. In addition, an alternative extraction system that utilises a commercially available graphitisation system was also investigated. The precision obtained from both methods was 2 h which is within the World Meteorological Organisation (WMO) guidelines. The final step is the calculation of f f CO2 mole fraction including the calculation of the corrections for other influences on 14C. Data from the GAUGE campaign was used to calculate the required corrections and f f CO2 mole fractions. Consideration of the spatial and temporal 14C emissions from nuclear power stations is required. There is high temporal variation in the emissions from the nuclear power stations that was considered in this thesis by using daily emission data. Sporadic high emissions from the nuclear power stations occur. However, if samples are taken to avoid these, the nuclear correction is of similar magnitude to the correction required for biospheric disequilibrium. The correction required for biospheric disequilibrium was also investigated as part of the work in this thesis using three different biospheric models. Overall, this thesis has contributed to the use of ∆ 14CO2 to quantify f f CO2 emissions in the UK. It has built on work from a previous project and the improvements made as part of this thesis will be used in a future project to use ∆ 14CO2 measurements to improve the verification of f f CO2 emissions using atmospheric measurements and modelling.

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.

The Fischer-Tropsch process has the potential to be fundamental to a future without dependence on fossil fuels. It converts syngas, a readily available resource, into high quality hydrocarbons, with water being the primary byproduct. Like many gas-to-liquid processes, it is catalysed on a transition metal surface, and the lifetime of the catalyst bed largely dictates the process’s economic viability. Predictive computational models can shed light on the mechanisms driving catalyst deactivation. This work focuses particularly on reactors with a titania-supported cobalt catalyst. One part of this project is an investigation using VASP studying the adsorption and mobility of several cobalt species that might form on the TiO2 support surface. It is found that reactor species generally have a strong effect on the binding properties of cobalt, and that this effect could either strengthen or weaken its bond to the surface depending on how reactive the functional group is with the support surface. In particular, the carbon monoxide feedstock was found to favourably bind to surface- adsorbed cobalt and create highly mobile species. In practice the support surface is rarely dry, and this effect is also found on a model hydrated surface. This painted a clear picture that the carbon monoxide feed may have an effect on the sintering process by inducing surface and gas-phase transport of highly dispersed cobalt. Plane-wave DFT suffers from unfavourable cubic scaling and its extended basis makes vacuum space costly, limiting its applicability to large clusters and surface structures. The linear-scaling DFT code ONETEP is a good candidate for investigating these classes of system. While its metals treatment for systems smaller than the thousands of atoms scale using ensemble DFT (EDFT) is also cubic-scaling, it is able to offload a lot of the cost of the calculation onto linear-scaling parts and also maintains a linear-scaling memory cost. Another part of this project was to develop ONETEP to be able to perform studies of chemistry on adsorbed and free catalyst nanoparticles. Two main pieces of crucial functionality have been added to ONETEP - free-spin EDFT and nudged elastic band transition-state searching. The former allows ensemble DFT to be performed at non-integer net spin and non-integer charge, and also adds the ability to relax the spin state during a calculation - previously ONETEP was constrained to fixed integer net spin. This is crucial in cases where the net spin of a magnetic system is not necessarily known or may be altered by, for example, surface adsorbates. The latter is a popular and robust transition state searching method that reliably minimizes a path connecting a product and reactant. The dimer method is also being developed for ONETEP primarily as a transition state refinement tool. Early applications of the new functionality in ONETEP is demonstrated in an investigation of carbon monoxide binding on cobalt HCP and FCC nanoparticles of around 50 atoms. These adsorption energies are compared, where available, to surface adsorption energies from literature. Generally, the abundance of edges on these small particles make surface adsorption energies site dependent and different to clean surface values, and adsorption sites near edges are generally stronger than the surface values. Additionally, two CO dissociation pathways on the FCC cluster are examined, starting from the surface making up the majority on the FCC Wulff particle. A modest decrease in activation energy is identified, and the presence of new pathways involving particle edges is highlighted for future study.

The production of energy and chemicals using dwindling fossil feedstock reserves (oil, gas and coal) has generated global environmental and energy security concerns. This has motivated research into alternative energy technologies and sustainable products and processes. Over the past few decades, research and interest in biomass as a renewable feedstock has exponentially grown. Bio-oil from biomass is particularly interesting as it can be used for energy, chemicals, or as an energy carrier. However, crude bio-oil possesses certain physical and chemical properties which prevent its direct application and integration into existing fuel infrastructures. For example, the high acidity of untreated bio-oil can cause corrosion of vessels and pipework. Therefore, a detailed study which aimed to improve the properties of bio-oil using methanol, ethanol and isopropanol for bio-oil blending and supercritical upgrading was conducted. The results showed supercritical methanol treatment eliminated the acids and improved the pH of the bio-oil. However, the crude bio-oil contained 37.03 % phenols which did not transform after blending with alcohols or after supercritical upgrading. Therefore, the research aimed to convert phenol to less reactive compounds such as cyclohexanol in order to improve the bio-oil properties. A process of in situ catalytic hydrogenation of phenol using aqueous phase reforming of methanol for the hydrogen source achieved high cyclohexanol yield (93.35 %) and selectivity (94.23 %).A new process of producing industrially desirable and valuable chemicals including methyl isovalerate and a mixture of monoterpenes (p-Mentha-1,4(8)-diene, D-Limonene, and y-Terpinene) from a bio-oil based compound (geranyl isovalerate) was reported in Chapter 6. No catalyst was used, and subcritical water performed the role of catalyst and co-solvent with supercritical methanol. Very high geranyl isovalerate conversions was achieved as less than 3% of it was detected in the products and methyl isovalerate and the monoterpenes accounted for 97%.

The utilisation of edible resources as alternative and renewable sources of energy and chemicals in the battle against climate change is unsustainable and poses a potential threat to food security. As such, the use of waste-derived resources (whether plastics, biomass, or metals) is at the forefront of sustainable technology research today, owing to the abundance of waste and the need to reduce reliance on fossil resources. This research, therefore, exploited the potential to convert (via liquefaction) lignocellulosic biomass to valuable products that could serve as precursors to the chemical and fuel industries. Specifically, pine needles (exemplar forest waste) and sugarcane bagasse (an agricultural waste) were employed as feedstock in this work. The influence of various low-cost solvents (glycerol, ethylene glycol, and water) used as liquefaction solvents and reaction conditions (temperature, pressure, and catalyst) on both biomass conversion and product yields were investigated. In this study, sugarcane bagasse was found to be predominantly cellulosic in nature whereas that of pine needles was more ligninic. The application of water as liquefaction solvent facilitated better degradation of cellulose and hemicellulose whereas glycerol and ethylene glycol were found to facilitate better degradation of the most recalcitrant biomass component, lignin. As such, the highest biomass conversion was achieved in the presence of glycerol (94 wt.%) followed by ethylene glycol (86 wt.%), and water (76 wt.%) at 250 °C, 1 h reaction time, 30 bar initial helium pressure, and biomass:solvent ratio of 1:10 (wt:wt). Acetic acid, glucose, levulinic acid, phenol, and various esters were the most prominent biomass-based products identified in the liquid fraction, all of which are important platform chemicals for industry. It was also observed that the use of water enhanced the selectivity of the targeted biomass derivatives; particularly, acetic acid, phenol, and levulinic acid. Meanwhile, glycerol and ethylene glycol were found to generate additional valuable chemicals through various side reactions. Hence, a novel one-pot process was designed for the simultaneous valorisation of biomass and glycerol using acetone as a cosolvent and reagent. This process produced mainly acetic acid and phenol as biomass-based chemicals while solketal and mesityl oxide were synthesised from the excess glycerol and acetone. The one-pot valorisation of biomass and low-value solvents such as glycerol would potentially significantly reduce the number of steps needed to achieve the same results in separate processes, making future biorefineries more economical. Finally, it was discovered in this research that bio-char formed in situ during biomass liquefaction is catalytically active towards the conversion of liquefaction solvents to value-added chemicals. The activity of the bio-char was largely attributed to its ash content. This catalytic activity was particularly observed in the conversion of acetone to mesityl oxide. Consequently, the potential role of biomass and its components; bio-char and ash as a heterogeneous catalyst for mesityl oxide synthesis was demonstrated in this thesis for the first time. The application of catalysts from renewable and environmentally friendly sources in place of fossil-derived catalyst or expensive precious metals is crucial for future research in light of the development of a sustainable industry.

Microalgae are positioned as a promising platform for sustainable biofuels production due to their ability to synthesise starch and lipid molecules, which can be directed towards the production of bioethanol and biobutanol via fermentation, or biodiesel via transesterification. The commercialisation of microalgal biofuels, however, is unlikely to become a reality unless large-scale algal cultivation systems can efficiently generate high-density algal cultures rich in starch and lipids. Numerous metabolic studies have revealed the ability of cells to counteract nutrient-stressed conditions by inducing starch and lipid accumulation, allowing the exploration of tailor-made biofuel-oriented cultivation strategies. Nevertheless, it has been demonstrated that those conditions that favour starch and lipid formation do not typically favour biomass growth, complicating the identification of cultivation strategies fit for biofuels production. In this research, the challenging identification of optimal cultivation strategies maximising starch and lipid formation is approached by developing a predictive kinetic model supported by experimental observations and suitable for the simulation and optimisation of algal mixotrophic growth dynamics co-limited by nitrogen and phosphorous. The model uses a compartmentalised approach in which cells are comprised of an active biomass fraction and storage molecule fractions, allowing the identification of the individual starch and lipid concentration profiles. To construct and validate the model, laboratory-scale batch experiments were carried out with the green model species Chlamydomonas reinhardtii under various acetic acid (i.e. carbon substrate), nitrogen, and phosphorous concentration regimes. The model was then built in line with experimental data and existing modelling approaches, and the associated kinetic parameters were quantified via an optimisation-based fitting methodology. The validated model was subsequently exploited as an optimisation tool by identifying the required nutrient compositions maximising starch and lipid formation. These optimised scenarios yielded significant increases in starch (+ 270 %) and lipids (+ 74 %) compared to the non-optimised strategy. The model's predictive capacity for fed-batch cultivation dynamics was additionally assessed via the evaluation of a nutrient feeding strategy consisting of intermittent pulses of acetic acid. Such a strategy was found to significantly increase biomass formation (+ 126 %) against standard batch cultivation. Finally, a case study was carried out to quantify the production of biobutanol and biodiesel within the framework of a microalgal biorefinery. Results showed biofuel yields (g fuel per g of dry algae) of 0.103 biobutanol via the ABE fermentation of microalgal starch, and 0.038 biodiesel via the transesterification of microalgal lipids. In summary, this research presents an optimisation framework combining both modelling and experimental tools which can be systematically applied for the establishment of optimal biofuel-oriented microalgal cultivation systems and additionally reaffirms the exploitative value of microalgae as a promising biorefinery platform for biofuels production.

Microalgae are a promising 3rd generation feedstock for biofuel production. However, their harvesting according to literature is uneconomical contributing up to 25% of the total cost of biofuel processing. In addition, the drying and solvent extraction step is energy intensive. Therefore, this research aimed at overcoming these challenges through the application of magnetic nanoparticles (MNPs) for algal separation, catalytic hydrothermal liquefaction and in ionic liquid (IL) lysis of magnetically separated microalgae. The MNPs were synthesized by co-precipitation and used to separate microalgae from culture medium at a separation efficiency of over 95%. The microalgae/MNPs slurry was subjected to HTL and IL treatment in separate experiments. In the HTL process, the microalgae/particle slurry was converted to biocrude oil and a biocrude yield of 37.1 wt.% was achieved in presence of MNPs while microalgae only yielded 23.2%. The percentage areas in the GC-MS chromatogram corresponding to hydrocarbons (HCs) in Zn-ferrite catalysed and uncatalysed biocrude were 46.5% and 19.9% respectively. Heteroatom compounds in the biocrude oil reduced substantially when liquefaction was done in the presence of Zn/Mg ferrites. The MNPs were recovered from solid residue by sonication and recycled. To further reduce N and O content of biocrude, the effect of HTL conditions on yield and biocrude composition was also investigated. HTL under 5 wt.% sulphuric acid reduced the nitrogen content of biocrude by 83 wt.%. In addition, increasing liquefaction time led to a gradual reduction in the N, O and S content of the biocrude. Moreover, HTL under 30 bar hydrogen atmospheres resulted in increased biocrude yield compared to HTL in absence of hydrogen. ILs were also used for lysis of magnetically separated microalgae to efficiently extract lipids. GC-MS, FT-IR and 1H NMR analyse was done on the extracted lipids. The MNPs were recovered from algal residue by sonication in DI water. TGA analysis of recovered MNPs confirmed absence of algal biomass on the MNPs. These were then recycled to harvest more microalgae at a separation efficiency of 96%. The ILs were also recycled and 1HNMR, mass spectrometry and FT-IR analysis confirmed absence of structural alterations in the recycled IL. Finally, the effect of process conditions on yield of extracted lipids was also investigated. Application of MNPs in magnetic separation of microalgae, catalytic HTL and IL extraction will potentially reduce the processing cost of biofuels from microalgae. This would result in biofuels being more competitive with petroleum-derived fuels.

In this project, a non-thermal plasma dielectric barrier discharge (“DBD”) reactor was used to reduce the concentration of tar in the product gas, and its performance was evaluated at different reaction conditions. Toluene and benzene were used as tar model compounds. The effects of reaction parameters such as the residence time, concentration, wall temperature and plasma power on tar removal were studied in a tubular dielectric barrier discharge (DBD) plasma reactor at ambient pressure. The percentage removal of tar increased with increasing plasma power and residence time to as high as 99% in various carrier gases (CO2, H2, and N2) and gas mixtures. However, the decomposition of tar analogue compounds decreased with increasing concentration. It was found that most of the toluene converted into solid residue due to the polymerization of hydrocarbon radicals produced in the plasma system at ambient temperature in all carrier gases (CO2, H2, N2, and mixtures). The other products were lower hydrocarbons, CO, and H2, depending upon the type of carrier gas. The synergetic effect of power and temperature was investigated to decrease the unwanted solid deposition. It was observed that selectivity to lower hydrocarbons increased to 99% at 400 oC and 40 W, with the non-thermal plasma. In these conditions solid formation was completely prevented. The maximum selectivities to methane were 60 % and 81% for toluene and benzene, respectively. However, in other carrier gases (N2 and CO2), the selectivity did not increase beyond 15 %, even with increasing temperature, and solid formation was observed even at elevated temperatures. However, in the gas mixtures, solid formation was significantly reduced when increasing the temperature due to presence of H2. Therefore, the plasma power and surrounding temperatures can be used to control the product distribution in the presence of H2 carrier gas.

Biodiesel is a renewable alternative to ‘petro-diesel’. There is already an established, conventional production technology based on refined vegetable oils. However, this is always more expensive than producing petroleum-based diesel, mainly due to the feedstock cost. Use of a cheap, non-edible feedstock, such as waste shark liver oil (WSLO), would reduce the biodiesel production cost and make the process economically viable. WSLO is obtained by exposing sharks’ livers to the sun until they melt and collecting the oil produced. Sharks’ livers comprise 25-30% of their body weight. Historically, the discarded WSLO was used for waterproofing wooden boats. However, this application is no longer required, as modern boats are made of fibreglass. The excess WSLO derived from these discarded sharks’ livers has great potential for being further processed into valuable products, including biodiesel, squalene and omega-3 polyunsaturated fatty acids (PUFA), such as eicosapentaenoic (EPA) and docosahexaenoic (DHA). The glyceride components of the WSLO can be converted into biodiesel using existing biodiesel processing technologies, while the squalene, EPA and DHA may be extracted and sold as value-added products through biorefinery processes. This study investigated the production of fatty acid methyl ester (FAME) from WSLO using both acid (sulfuric acid, H2SO4) and base (sodium hydroxide, NaOH) catalysts. Due to the high levels of free fatty acids (FFA) in WSLO, homogeneous alkali-catalysed transesterification was less effective than the acid-catalysed process, resulting in a maximum WSLO to FAME conversion of only 40% after 15 min at a 60°C temperature, a 1.5 wt.% of NaOH catalyst and a 6:1 molar ratio of methanol to WSLO. The acid-catalysed transesterification of the WSLO was investigated, using Design of Experiments (DoE), by a response surface method. The acid-catalysed process achieved 99% FAME conversion during a 6.5 h reaction time at a 60°C temperature, a 5.9 wt. % of H2SO4 catalyst and a 10:3 molar ratio of methanol to WSLO. Saponification of WSLO for extracting squalene was also investigated using a DoE methodology to obtain the operating conditions for highest squalene extraction. The results showed 101.6 ± 1.3 % squalene recovery at the following operating conditions: a 5 min reaction time, a 9.9 wt. % of water loading and a 20:1 molar ratio of ethanol to oil. Aqueous silver nitrate (AgNO3) was employed for extracting EPA and DHA from fatty acid ethyl esters produced from the WSLO. The highest EPA and DHA recoveries achieved were 66.2% EPA and 83.4% DHA. These came from extractions using a 2 h reaction time, a mixing speed of 300 rpm, a 20°C reaction temperature, and a 50 wt. % of silver nitrate concentration. Techno-economic analysis was performed to assess the commercial feasibilities of acid-catalysed biodiesel production using WSLO and alkali-catalysed biodiesel production using refined vegetable oil (rapeseed oil). Aspen HYSYS-V9 was used to simulate both production types at plant capacity of 12,000 te/y and lifespan of 20 years. Net present values (NPVs) of US $34.8 and US $4.9 million were obtained for the acid-catalysed WSLO process and the alkali-catalysed vegetable oil process, respectively. The internal rate of return (IRR) was calculated to be 260% for the acid-catalysed process and 56% for the alkali-catalysed process. Therefore, the acid-catalysed process is more profitable than the alkali-catalysed process due to its higher IRR percentage. Sensitivity analysis was also conducted to show the effect of certain variables on the NPV of both biodiesel production types. It was concluded that the biodiesel selling price has more effect on the NPV than the glycerol variation price, whereas the triglyceride feedstock purchase prices have the largest influence on the NPV of the two processes.

The transportation sector relies heavily on fossil fuels and contributes up to one third of greenhouse gas emissions. Among available renewable resources, only biomass contains the carbon and hydrogen that can be converted into multiple energy vectors (i.e. heat, electricity, biofuels and chemicals) to reduce the heavy dependency upon fossil fuels and their associated environmental impacts. Advanced thermochemical technologies, i.e. pyrolysis and gasification are considered as potential approaches to convert biomass into fuels for the transportation sector and chemical industry. Although, coal gasification is well developed, gasification of biomass has not been widely commercialised due to a number of challenges including low H2/CO ratios (less than 1), low H2 content (40-60 mol%), low biomass conversion (80-85%), low process efficiency (70-80%), high CO2 content (20-30 mol%) and high tar formation (30-80 g/Nm3). The aim of this study was to develop a modular gasification system to produce H2 from waste biomass/residues to be used as an energy carrier or converted further into synthetic liquid fuels (diesel fuel and gasoline) and valuable chemicals (i.e. methanol, ethanol and alcohol). Gasification of waste biomass was carried out in a two-stage gasification process in which feedstock was decomposed into intermediate products and subsequently gasified using steam. The effect of operating conditions in the pyrolysis and gasification steps on maximising the H2 production and quality of synthetic gas (known as syngas) as well as process efficiency was studied. The synergistic effect of CO2 environment and catalyst (Ni/MRM, Ni/Al2O3 and Ni/HZSM-5) on the gas properties and tar formation was evaluated. A small-scale air-blown throat downdraft gasifier was optimised using Computational Fluid Dynamics (CFD) to obtain high quality syngas/H2 production and validated using experimental and literature data. The pyrolysis temperature has a strong effect on char morphology and the volatiles produced, which in turn affected the syngas properties. Increasing pyrolysis temperature from 600 oC to 900 oC, resulted in an increase in H2 (from 54 mol% to 66 mol%) and CO (from 5 mol% to 10 mol%) and a reduction in CO2 (from 37 mol% to 22 mol%), CH4 (from 5 mol% to 2 mol%) and tar content (from 39 g/Nm3 to 24 g/Nm3) in the gas stream after gasification. Around 67 mol% H2 together with high carbon conversion (94%) and low tar formation (21 g/Nm3) were observed under N2/steam gasification at a pyrolysis temperature of 900 oC and gasification temperature of 1000 oC with steam to carbon in feedstock molar ratio of 5.7. A process efficiency of 84% was achieved in this case. Combining CO2 and steam in the gasification stage produced up to 78 mol% H2 with a low CH4 (0.9 mol%) and tar content (9 g/Nm3) with process efficiency ≤ 97% at a pyrolysis temperature of 900 oC and gasification ii temperature of 1000 oC with steam to carbon in feedstock molar ratio of 3.4. Less than 10 mol% CO2 was generated from CO2/steam gasification compared to 20-30 mol% in N2/steam gasification. Therefore, the use of CO2 in a gasification process could be route to utilise waste CO2 for H2 production from biomass/waste, contributing significantly to the environmental footprint and sustainability of the process. Adding a Ni-based catalyst in the process had no effect on the syngas properties, but reduced by 2-3 times, the amount of tar (particularly heavy PAH compounds). The use of the Ni/MRM catalyst (waste product of bauxite processing) proved to be successful for the removal of naphthalene constituents (58%), the main component in tar, compared to only 50% reduction for the commercial Ni-based catalysts (Ni/Al2O3 and Ni/HZSM-5). For a small-scale air-blown throat downdraft gasifier, a throat to gasifier diameter ratio of 0.4 and the position of the air inlet nozzles at 10 cm above the throat provided high quality syngas/H2 production. The modelling can be used to predict the syngas compositions under the various operating conditions and provides an operating window for the development of a simple, highly efficient and robust gasification unit that can be used for H2 production without major downstream processing to remove impurities.

This research investigated anaerobic digestion (AD) with various types of lignocellulosic biomass feedstocks from Nigeria, and the potential use of low-cost ash-extracts produced from agricultural biomass, such as empty palm bunch, cocoa pod, banana peel, for the enhancement of AD biogas production. Experiments investigated co-digestion mixtures, comprising several tropical grass silages and cassava processing wastes in CSTR under mesophilic and thermophilic temperatures, at an organic loading rate of 2.0 gVS.L-1.d-1 and 20 d HRT. Under each temperature regime, two pairs of 1 L CSTR were used – one pair as control, and the other pair supplemented with biomass ash-extracts. The experiment was run for three HRT, all reactors achieving steady-state operation during the third HRT cycle. At steady-state, the specific methane production (SMP) recorded in the thermophilic reactors, was 299.9 and 338.2 N mL CH4.g-1VS added. d-1 for the control and the supplemented pairs of reactors, respectively, indicating that methane production had increased by 13% due to ash-extract supplementation. Similarly, for the mesophilic reactors, the SMP was 297.9 and 330 N mL CH4.g-1VS added. d-1 for the control and ash-supplemented reactors respectively, signifying that ash-extracts improved mesophilic CH4 production by 11%. Statistical comparison of CH4 production in control and ash-supplemented reactors showed p-values ≤ 0.05 for both temperatures, which confirms that ash-extracts improved biomethane production significantly. Supplementing different feedstocks, such as gamba grass, guinea grass, elephant grass, rice straw and cassava processing wastes, with ash-extracts in both BMP batch assays and CSTR, also gave enhanced methane production. From the chemical analysis data and literature, it was possible to conclude that biomass ash-extracts appear to provide both alkalinity and/or trace metals for the enhancement of methane production when digesting agricultural wastes as both mono-substrates and co-digestion mixtures. The low cost of biomass ash-extracts compared to commercially available chemical additives, i.e. alkali and trace elements, make them economically feasible AD supplements for improving methane production from a wide range of grass biomass and other agricultural wastes in developed and developing countries.

Climate change is regarded as the greatest threat to the World’s ecosystem and hence to the sustainability of human life. Because anthropogenic emissions of greenhouse gasses are held largely responsible for the enhanced greenhouse effect, the international community has committed to reduce emissions, and in particular, to replace fossil fuels with low carbon renewable sources (COP 21 Paris agreement, 2015). Biofuel is a candidate technology, and the concept of growing energy crops represents significant opportunities. This project aimed to examine the risk that climate change pose to the value of growing energy crops. The concern is that climate change could reduce yield sufficiently for the crop to give less energy than expected, and possibly less energy than was put into growing it, further increasing the carbon footprint. Clearly, this situation is unacceptable. In order to assess the overall energy balance and carbon footprint, farm practices; fertilizer application and tillage management were accounted in the overall life cycle assessment. Thus, this thesis reports the first fully integrated framework for the assessment of the impact of climate change on growing biofuels under various farm management practices. Climate change impacts on yield varied depending on future GHG scenario pathway and timeline. The LCA results indicate that synthetic fertiliser application contributed the greatest percentage to the total GHG emission, averaging 57.7%of the total GHG emissions, of which 53.4% came from direct and indirect N2O emissions and 4.3% from CO2 emissions as a result of urea application. The remaining 42.3% of emissions came from input production (37.8%) and field operation (4.4%).Although increasing fertiliser application contributes to yield increase, the overuse of chemical fertilisers has a greater negative impact on the environment as the results indicate. In particular, the rate of fertiliser application is optimal at 160 kg per hectare, and generally, this project has determined that yield is more sensitive to fertiliser than to climate change, whilst climate change is the causal driver for the increase in net energy and carbon footprint at most locations. The integrated framework developed for this project has been validated and tested using maize, but can be applied to other biofuel crops provided that the proposed location has historical weather data, information about soil type and farm management details of the proposed crop type. Given the absolute importance of reducing carbon emissions.

To evaluate the biomass potential to provide thermal energy to drive an absorption refrigeration system, a computer aided model was developed. The subroutines that constitute the model agree with ASHRAE standards and reflect the underlying thermodynamic principles, but introduces a shorter method of analysing Aqua Ammonia absorption refrigeration cycle by eliminating the need for finding the specific volume from charts or computation of the rigorous parameter components of the equations of state. Parametric evaluation from the model shows that at constant evaporator, condenser and absorber temperatures, the COP decreases with increase in generator temperature. The COP ranges between 0.84 for generator temperature of 60◦ C and 0.76 for 90◦ C, beyond which the variation is insignificant. The concentration of the refrigerant exiting the generator is dependent on the solution mass flow and temperature, and varies between 0.9 to 0.98 for the simulated data. This quantity is usually assumed to be 100%. The biomass consumption varies with generator temperature and the flow of hot water, but also depends on the fuel density, load and heating hours, as well as the efficiency of the biomass combusting system. The rationale a typical (African) rural community with access to biomass is based on the characteristics of these communities; one of which is the access to renewable energy in a dimension that is apt to support the production and efficient utilisation of the energy to a large scale, and the need for a refrigeration system that demands little or no extra energy but capable of conditioning indoor climate to suit human comfort, maintain and support the viability of agricultural seedlings and medical drugs in healthcare facilities and related amenities. The conventional vapour compression refrigeration systems, although efficient, use refrigerants that are not environmentally friendly and high energy consuming. The study highlights some of the limitations of the uptake, and efficient utilisation of renewable energy in the region. It also presents a review of energy in the region from a global and historical perspective and focuses on the influence on the regional economy from a state of the art review of the literature. It shows the relation between energy access and economic development. Causality study shows that this might be unilateral or bilateral, but the influence of one on the other does exist. The theory of biomass for energy was explored to highlight measures of enhancing the energy yield of a biomass species, suitability and selection.

Microbial electrosynthesis (MES) which uses microbes and electricity to generate high grade chemicals could contribute to the reduction of greenhouse emissions as it uses CO2 in the process. The implementation of this technology on an industrial scale could be on the horizon. Currently, little is known about the environmental loads associated with the successful scale up of the technology with regards to global warming potential and other environmental burdens. Such knowledge is needed in order for relatively new bioprocesses like MES to be sustainably scaled up and industrially applied. This research conducted an empirical and environmental investigation of MES for the synthesis of chemicals from CO2. Experimentally, MES for bio production of chemicals from CO2 was investigated using mixed culture as biocatalyst. CO2 introduced into H-shaped bioelectrochemical systems produced methane, formic, acetic and propionic acids more readily however under some conditions isobutyric acid and ethanol were synthesized. Different polarizations (-0.8V, -1.0V, -1.2V and -1.4V vs Ag/AgCl) and temperatures (27oC and 40oC) were used revealing that bioproduction was affected by changes to these parameters. Biofilm growth and gradual acclimation to CO2 achieved a maximum production rate of 3677μM/day at -1.4V vs Ag/AgCl and 40oC. However an average decline of 18 percent in the coulombic efficiency was observed when the potential was reduced by 0.2V.This showed that there may be energy and environmental risks associated with products synthesized at lower potentials needing confirmation by an environmental analysis. The environmental impacts of products synthesized through MES were examined by modelling a simulated industrial plant (1000 tonnes/year). Environmental analyses were used to reveal the main products to target for MES. Different MES plants generating a range of biochemicals were modelled considering two sources of energy (natural gas and UK national grid), one at a time. This gave specific and detailed scenarios that allowed comparison of the environmental impacts. Results shows that the synthesis of acetic acid, propionic acid, ethanol and methanol released more carbon dioxide than it used for both natural gas and the UK national grid. However, formic acid (-3,421 tonnes CO2 eqv) was found to be the only product having a negative global warming potential using natural gas and comparatively low environmental impacts in other environmental categories. It was concluded that formic acid synthesis through MES is a more suitable product than the other biochemicals analysed in terms of energy efficiency, global warming potential and other potentially harmful environmental impact categories.

The depletion of fossil fuels coupled with the growing demands of the world energy has ignited the interest for renewable energies including biomass for energy production. A reliable affordable and clean energy supply is of major importance to the environment and economy of the society. In this context, modern use of biomass is considered a promising clean energy alternative for the reduction of greenhouse gas emissions and energy dependency. The use of biomass as a renewable energy source for industrial application has increased over the last decade and is now considered as one of the most promising renewable sources. The direct combustion of biomass in small scales often results in incomplete and inconsistent burning process which could produce carbon monoxide, particulates and other pollutants. Therefore, biomass is required to be transformed into more easily handled fuel such as gases, liquids and charcoal using technologies such as pyrolysis, gasification, fermentation, digestion etc. Biomass gasification upon which this thesis focuses is one of the promising routes amongst the renewable energy options for future deployment. Gasification is a process of conversion of solid biomass into combustible gas, known as producer gas by partial oxidation. This research work is carried out to investigate various methods employed for modelling biomass gasifiers, it also studies the chemistry of gasification and reviews various gasification models. In this work, a mathematical model is developed to simulate the behaviour of downdraft gasifiers operating under steady state and determine the synthesis gas composition. The model distinctly analyses the processes in each of the three zones of the gasifier; pyrolysis, oxidation and reduction zones. Air is used as the gasifying agent and is introduced into the pyrolysis and oxidation zones of the gasifier for both single and double air operations. These zones have been modelled based on thermodynamic equilibrium and kinetic modelling; the model equations are solved in MATLAB. Given the biomass properties, consumption, air input, moisture content and gasifier specifications, the MATLAB model is able to accurately predict the temperature and distribution of the molar concentrations of the synthesis gas constituents. The downdraft gasifier is also represented in Aspen HYSYS based on the same models to study the effect of both single and double air gasification operation. For known biomass properties, consumption, air input, moisture content and gasifier operating conditions, the Aspen HYSYS model can accurately predict the distributions of the molar concentrations of the syngas constituents (CO, CO2, H2, CH4, and N2). The models were validated by comparing obtained theoretical results with experimental data published in the open literature. Parametric studies were carried out to study the effects of equivalence ratio, moisture content, temperature on the gas compositions and its energy content. The proposed equilibrium model displayed a variable ability for the prediction of various product yields with this being a function of the feedstock studied. It also demonstrated the ability to predict product gases from various biomasses using both single and double stage air input. In the case of gasification with double air stage supply, higher amounts of methane are obtained with specific tendencies of the gases reaching a peak at certain conditions. The kinetic model was partially successful in predicting results and comparable with experimentally published results for a range of conditions. There were discrepancies particularly with CH4 formation and the operating temperatures predictions which were usually consistently lower than those actually measured experimentally. The use of the PFR, however, did show a greater potential for the use in further modelling.

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.

Wood from coniferous trees is an important source of renewable biomass. It can contribute to provision of carbon neutral energy, biomaterials and housing for a growing population. Softwood is mainly composed of cellulose, galactoglucomannan, xylan and lignin. This thesis focuses on the biosynthesis and function of Glucuronic acid (GlcA) decorations on softwood xylan. Results demonstrate that this GUX (GlucUronic acid substitution of Xylan)-dependent xylan branching is critical for the maintenance of biomass recalcitrance in a model vascular plant Arabidopsis thaliana. Experiments employing in vitro and in planta activity assays show that conifer transcriptomes encode at least two distinct GUX enzymes which are active glucuronosyltransferases. Interestingly, these enzymes have different specific activities, with one adding evenly spaced GlcA branches and the other one being able to add consecutive decorations. It is possible that these different patterns of xylan branching may have an impact on ability of xylan to interact with cellulose fibrils. To investigate the role for xylan binding to cellulose, Arabidopsis mutant plants in which this interaction is lost were evaluated alongside transgenic mutant lines in which the interaction may be restored. Results of this analysis indicate that the presence of cellulose-bound xylan might have an influence on plant vasculature integrity and thus it may have an effect on plant growth and biomass properties. Moreover, further results indicate that some xylan cellulose interaction is likely to occur in cell wall macrofibrils which can be detected in softwood. Taken together, this thesis provides insights into the process of conifer xylan glucuronidation and the possible role these branches may be playing in the maintenance of softwood recalcitrance and mechanical properties. In addition to identifying potential mutagenesis targets for improving softwood processing, this work is a proof of concept for the use of GUX enzymes for in vivo and in vitro biosynthesis of novel xylan structures with potential industrial application.

Wax anti-settling additives (WASA) are used to mitigate against the problems caused by the settling of n-alkane wax crystals, which crystallise from petroleum diesel. This can result in the blocking of fuel filters and hence vehicle failure. However, the mode of action for such additives is not currently known and two mechanisms have been proposed: they reduce the wax crystal size to such an extent that they settle very slowly; or they induce gelation in the wax suspension. This project aims to elucidate the mechanism of WASA within the diesel system. A room temperature crystallising model diesel (10 wt% n-alkanes in dodecane) has been developed. This model system has given a good response to the additives, with the wax crystals reduced in size, and is hence suitable for mechanistic studies. Differential scanning calorimetry and infra-red spectroscopy both suggest that the WASA is incorporated in or onto the wax crystal. DSC shows that small amounts of WASA suppress the wax crystallisation temperature and change the shape of the heat flow curve. FT-IR shows the WASA amide stretch present within filtered and dried wax crystals. Intriguingly, electrophoresis experiments show that the WASA imparts a positive charge to the wax crystals, suggesting an electrostatic role in the WASA action. Rheological experiments show the presence of a weak gel in the WASA doped model diesel. However, the gel strength is not altered by the presence of an organic salt and thus cannot be purely electrostatic in origin. Small angle neutron scattering has been conducted to help locate the WASA in the system. It has shown that in solution WASA shows a collapsed polymer coil structure with a single molecule occupying a 28 Å diameter sphere and multiple WASA molecules forming a 2400 Å diameter sphere. In the presence of the wax the WASA scatter does not significantly change suggesting that the WASA is on the surface of the wax crystal. By combining these results, a mechanism of WASA action is proposed as WASA cations interactions bridging between the wax crystals causing a weak bridging flocculation gel with electrostatic and steric effects contributing to stabilisation. The WASA charges are partially dissociated thus giving the electrophoretic effect and the long chains on the cations can contribute to stability via steric stabilisation.

Energetic materials (explosives, propellants and pyrotechnics; EMs) encompass a broad range of materials. These materials are used across a wide spectrum of applications, including civil and defence. For example, HMX, RDX and TNT are well known EMs with defence applications. Silver fulminate is instead used in house-hold Christmas crackers and ammonium nitrate is used for numerous industrial applications. Common to all EMs is their propensity to rapidly release energy upon external perturbation. The amount and type of energy that is required to initiate an EM can vary across orders of magnitude. Some materials (e.g. triaminotriperoxide, TATP) initiate with < 1 J of impact energy, while others (e.g. triaminotrinitrobenzene, TATB) cannot be initiated without > 100 J of impact energy. Understanding which materials can be handled safely is therefore of critical importance for maintaining the safe use of EMs across all sectors. Current trends in EM research include a drive to develop new materials with decreased sensitivities. While it is relatively straightforward to selectively modify some properties (e.g. environmental impact), very little is understood about what constitutes a sensitive material. At present, a new EM must be synthesised and its sensitivity tested. However, with no a priori knowledge of the potential sensitivity of a novel EM, synthesis is accompanied by substantial hazard, as well as time and financial costs. It is therefore pressing to develop a fundamental understanding of what dictates a sensitive material, and hence develop a mechanism to predict these properties. A particularly promising model to explore impact sensitivity of EMs is based on vibrational up-pumping, i.e. the up-conversion of vibrational energy. This thesis explores the application of this model to a set of azide, organic molecular and polymorphic materials. Azide-based EMs share the common N3− explosophore. The electronic structure of this anion was followed as a function of its normal modes of vibration. It was found that excitation of the bending mode is sufficient to induce athermal electronic excitation of the molecule, and spontaneous decomposition. This is valid both in the gas and solid states. It is therefore suggested that this vibrational mode is largely responsible for decomposition of the azide materials. Based on calculations of the complete phonon dispersion curves, the various pathways to vibrational energy up-pumping were explored, namely via overtone and combination pathways. In particular, the relative rates of up-pumping into the N3 − bending mode were investigated. Remarkable agreement is found between these up-pumping rates and the relative ordering of the impact sensitivity of these azides. The calculated vibrational structures of organic molecular EMs were first compared with experimental inelastic neutron scattering spectra and found to provide accurate representation of the low temperature vibrational structure of these complex crystals. The decomposition pathways for organic EMs are not known and hence no target frequency could be unambiguously identified. Instead, the up-pumping model was developed for these materials by investigating the total rate of energy conversion into the internal vibrational manifold. A number of qualitative trends were identified, which may provide a mechanism for the rapid classification of EMs from limited vibrational information. The overtone pathways were found to offer a good agreement with experimental impact sensitivities of these compounds. However, the increased complexity of the vibrational structure of the organic EMs as compared to the azides required a more thorough treatment of the up-pumping mechanism to correctly reflect experimental sensitivities. The effects of temperature on up-pumping were also explored. The sensitivity of organic EMs is known to differ across polymorphic forms. Most notable are the HMX polymorphs. The calculated vibrational structure of two HMX polymorphs was confirmed by inelastic neutron scattering spectroscopy. The up-pumping model developed for molecular organic EMs was therefore extended to a comparison of these two HMX polymorphs. The polymorphic forms of FOX-7 were also investigated under the premise of the up-pumping model. Upon heating, FOX-7 undergoes two polymorphic transformations, which increases the layering of the materials. It therefore offered an opportunity to explore the widely-held hypothesis that layered materials are less sensitive than non-layered materials. The metastable γ-form was successfully recovered, and its experimental impact sensitivity investigated by BAM drop-hammer method. However, upon impact, the γ- polymorph appeared to convert to the α-form and initiate at the same input energy. Hence a considerable deficiency of experimental methods is identified when studying polymorphic materials. FOX-7 was therefore explored within the framework of the up-pumping model. The inelastic neutron scattering spectrum was collected for γ-FOX-7, which confirmed the calculated vibrational structure. It was shown that within the up-pumping model, the layered γ-polymorph is predicted to be less sensitive than the α-form, and results from a decrease in the maximum phonon-bath frequency. Hence a new mechanism is proposed to describe the insensitivity of layered compounds. The work presented in this thesis explores the applications of vibrational up-pumping to rationalise and predict the relative impact sensitivities of a range of EMs. Despite the approximations employed in construction of the model, it leads to excellent correlation with experimental results in all cases. This work therefore opens the door to a new fully ab initio approach to designing new EMs based solely on knowledge of the solid-state structure.