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Hydrothermal carbonization (HTC) is a promising process for the upgrading of wet biomass residues. Models of HTC processes, in particular at continuous pilot-scale, are needed to move HTC from lab-scale to industrial scale. This study presents a process model for mild HTC, dewatering and conversion to intermediate energy carriers (bio-pellets and biogas for power and/or heat production) of three wet biomass residue streams: paper sludge, olive pomace and orange peels, based on lab- and pilot-scale experiments. In addition, the process energy efficiency and feedstock utilization of the HTC process is calculated and compared with conventional treatment options for the chosen residues, i.e., direct anaerobic digestion (olive pomace, orange peels) or combustion after conventional dewatering (paper sludge). The process model indicates that the HTC pilot-scale process is much more efficient in terms of feedstock utilization to produce heat and/or power than the reference scenarios. The process energy efficiency of the HTC process (pilot-scale) was calculated to be 26 %, 63 % and 40 % for paper sludge, olive pomace and orange peel feedstocks, respectively. For all feedstocks, both the solid and liquid-generated products are equally important for improving the overall process energy efficiency. This study demonstrates the potential benefits of HTC processes for upgrading wet biomass waste streams based on continuous pilot-scale data. • Hydrothermal carbonization successfully upgraded wet biomass residues for energy. • Hydrothermal carbonization was more efficient for heat/power than reference cases. • Solid and liquid products are both important to improve process energy efficiency. [ABSTRACT FROM AUTHOR]

Chemi-mechanical pulping (CMP) is a typical high-yield pulping technology to produce various papers and paperboards due to its high yield and high fiber properties. However, it is challenging to further improve its energy efficiency without the scarification of fiber quality. To attack this challenge, herein we study the effects of different hemicellulose pre-extraction on the viscoelasticity of wood cell wall, the energy efficiency, and product properties in chemi-mechanical pulping (CMP) process. Hardwood was first pretreated by NaOH to hydrolyze the benzyl ester bonds that link lignin with hemicellulose, aiming to partially remove hemicellulose and weaken the inter-fiber connections. Then, the hemicellulose-extracted wood underwent refining. The chemical distributions of wood, fiber morphologies, fiber surface fibrillation, energy consumption, and paper properties were extensively studied. The results showed that a 40.8% removal of hemicellulose corresponded to a 90.3% reduction in wood storage modulus (E') and a 68.3% decrease in specific refining energy consumption. Moreover, the weaker connections between microfibrils in the secondary layer, caused by hemicellulose extraction, promoted fiber surface fibrillation during pulp refining. The study elucidates the nonnegligible role of hemicellulose as the linking "bridge" between lignin and cellulose. It also provides a new mechanism in addition to the current classic pulping mechanism including lignin chemical/thermal softening and cellulose swelling in both CMP and chemi-thermomechanical pulp (CTMP). This study offers a feasible and efficient approach to extract hemicellulose from hardwood to reduce the refining energy without scarification of fiber quality, therefore, it holds promise for advanced and greener biorefineries. [Display omitted] • The mechanism of chemical-mechanical pulping about hemicellulose was supplemented. • Removal 40.8% of hemicellulose reduced wet woods' storage modulus by 90.3%. • LC ester bonds hydrolysis weakens connection inter-fibers and inter-microfibrils. • Wood de-hemicellulose optimized fiber separation and fibrillation in refining. [ABSTRACT FROM AUTHOR]

Densification is the most effective forming technology, the production of which, pellets are the most intensive energy content of biomass solid fuels. Increasing the overall utilization efficiency of bioenergy, extending available types of wastes and residues for pelleting, and improving the pellet quality comprehensively are necessary. This paper reviewed feedstocks used for pelleting, binding mechanism of biomass pellets, and evaluation systems of pellet qualities. To extend the supply amounts and improve the qualities of raw biomass, various feedstocks and formulation recipes were classified based on their regions, sources, and species. And applicable objects and conditions of several different pretreatment technologies for feedstocks were compared. Physical properties and biochemical analyses are also concluded to evaluate the flowability, compactibility, and potential characteristics as solid fuel. For a better understanding of energy consumption and conversion during the densification process, pelleting devices and binding mechanism are elaborated. Associations and differences between single pelleting press in lab-scale and industrial pelleting in pilot-scale are also discussed. Suggestions are proposed for the optimization design of pelleting devices and processes for different feedstock densification. Lastly, relationships between operating parameter factors of pelleting process and pellet quality are presented. This review could provide theoretical analyses for powder compression, new insights for waste to energy, and guidance for achieving global peak carbon and environmental strategic objectives. [Display omitted] • Biomass feedstocks and recipes used for pelleting are reviewed. • Pelleting process is explained from theoretical and experimental aspects. • Durability and water sorption of biomass pellets are discussed. • Suggestions are given for optimizing pelleting process and mechanical device design. • New methods and concepts in industrial pelleting are presented. [ABSTRACT FROM AUTHOR]

Abstract This paper provides a comprehensive review of 48 studies on the Life Cycle Assessment (LCA) of biogas production from 2006 to 2018 (13 years). The scope of the study, type of feedstock and impact categories used in the reviewed studies were discussed. Although various studies have been carried out to assess the efficiency and potential of wastes for biogas production, however, little attention has been paid particularly in the developing countries to conduct comprehensive analysis related to the environmental performance of biogas generation based on the LCA methodology. In Malaysia, the utilization of palm oil mill effluent (POME) as the source of energy has recently been expanded due to its abundant production at the palm oil mills. Therefore, this paper also highlights and discusses the feasibility of LCA approach on biogas production from POME as well as the opportunities and challenges from the Malaysian perspective. Highlights • Utilization of biogas production from organic waste to provide a clean energy. • Environmental performance of biogas as a renewable energy using an LCA methodology. • The trends of LCA approach in biogas production was reviewed worldwide. • The opportunities of biogas production from POME in Malaysian was discussed. • The feasibility of LCA approach on biogas production in Malaysian was discussed. [ABSTRACT FROM AUTHOR]

The interactions among chlorine (Cl), sulfur (S), and alkaline and alkaline-earth metals (AAEMs) are the critical factors that affect the formation, transformation, and deposition of ash during biomass and coal gasification and combustion. These issues cause slagging, agglomeration, corrosion, and other problems related to the safety performance of gasifiers and boilers. A better understanding of the determination methods, modes of occurrence, migration routes, and control technologies of Cl and S is the basis for clean and efficient utilization of biomass and coal. The paper summarizes the research work in this field, namely: (1) The modes of Cl and S occurrence in biomass and coal are introduced, mainly in different forms of inorganic and organic Cl/S compounds; (2) The principles, merits and demerits of quantitative determination methods for Cl and S are sorted out and compared; (3) The migration routes of Cl and S, mainly related to their modes of occurrence, reaction evolution, temperature, and atmosphere; and (4) The interactions among Cl, S, and AAEMs and its induced issues, especially the challenging problems related to ash, including alkali-induced slagging, silicate melt-induced slagging (ash fusion), agglomeration, and corrosion. Finally, ecological and technological significance of the Cl and S release is discussed. This knowledge is of great significance to effectively control the emission of Cl and S pollutants, stable operation of gasifiers and boilers, cleaner and more efficient utilization of coal, as well as to diminish the consumption of fossil energy and heighten the availability of renewable energy in such thermochemical conversion processes. • Migration routes of chlorine and sulfur are elucidated. • Interactions among chlorine, sulfur, and AAEMs are summarized. • Ecological and technical significance of chlorine and sulfur release is discussed. [ABSTRACT FROM AUTHOR]

Recirculation of hydrothermal carbonization (HTC) process water (PW) has been revealed as an effective strategy to promote the recovery of lost dissolved organics in the spent solvent. However, the role of operating parameters such as temperature, time and solid load during recirculation needs to be clarified and better investigated in order to achieve a successful PW valorization. In this paper, the effects of different reaction conditions during HTC with PW recirculation were studied by using orange peel waste as feedstock. The results showed that strong synergistic interactions occurred between the biomass and the recycled solvent, leading to a hydrochar mass yield increase between 0.5 and 11 wt% on a dry basis (d.b.), according to the reaction conditions. PW recirculation, especially at low conversion severity and solid load, increased hydrochar carbon content while drastically reduced the oxygen fraction. The reason was probably related to promoted dehydration and decarboxylation. As result, carbon and energy yields were respectively increased by 26.1 % and 27.0 %, on average. The energy balance outcomes showed that the energy recovery rose up to 8 times by recycling PW compared to phases with deionized water as HTC solvent. [Display omitted] • Hydrochar recovery enhancement is obtained by solvent recirculation. • Intense synergistic effects in hydrochar formation occur at low temperatures. • Dehydration and decarboxylation are promoted by solvent recycling. • Hydrochar carbon retention is increased by 6.2 % after recirculation at 180 °C. • Process water recirculation improves the conversion energy efficiency. [ABSTRACT FROM AUTHOR]

The European Union has set ambitious targets of raising the share of EU energy consumption produced from renewable resources from 20% by 2020 to 27% by 2030. The aim of this paper is to assess the role of woody biomass in renewable energy as gross final energy consumption in the European Union (the EU-28). The paper identifies leading and lagging countries in biomass development by focusing on their current biomass use and forecasts future perspectives. The research compares and evaluates the role of biomass in renewable energy in the EU-28 focusing on countries' potential resources and policy support. The study shows that all countries are making efforts to reach the 20% target in 2020 and exhibit a trend of increasing renewable energy as gross final energy consumption towards the new target of 2030. Solid biomass plays an important role in reaching the EU's renewable energy targets. The majority of the EU-28 countries are close to reaching their national renewable energy targets and show a very attractive biomass development. Unless energy consumption decreases however, some member states will face serious problems in reaching their renewable energy target in 2020. Following our analysis, the largest problems occur in those MS having a relative high-energy consumption pattern: France, Germany and the United Kingdom. It is unlikely that they can comply with expected renewable energy demand, unless they mobilize more woody biomass from their available domestic potential (France, Germany) or considerably increase their woody biomass imports (mostly wood pellets) from elsewhere (United Kingdom). [ABSTRACT FROM AUTHOR]

The application of compressed biogas (CBG) in day-to-day livelihood has garnered significant attention in modern day era. It is considered as a potential solution to curb the increasing energy demand and other environmental concerns. The process involves anaerobic digestion (AD) (hydrolysis, acidogenesis, acetogenesis and methanogenesis) of organic substrate under an optimum operating condition (pH, temperature, etc.) via anaerobic microorganisms. This paper aims to describe some major facts about different technological options related to pre-treatment, AD, cleaning and up-gradation system. It also highlights the practical challenges related to high investment cost, inadequate infrastructure, clearance and approval issues, poor feedstock supply chain management etc. in adaption of CBG plants in India. The review examines the significance of both dry and wet continuous digester systems, which includes its advantages and challenges, considering factors, such as feedstock characteristics, process stability, and operational efficiency. It was also found that the type of feedstock and its availability in existing market plays a vital role in smooth functioning of CBG plants. Therefore, the study presents a comprehensive review discussing potential feedstock readily available for CBG plants in Indian market. It was concluded that the usage of agricultural waste (such as Napier grass) has higher CBG potential compared to other feedstock. At the same time, the study presents a broader aspect to policy makers and governing authorities to reframe the existing structure for financial assistantship, regulatory laws, subsidiary schemes etc. for CBG plant owners. It also gives an opportunity to technocrats, industrialist and investors to come-up with an indigenous technology with in-house manufacturing units to promote CBG production in India. [Display omitted] • India has 46 compressed biogas plants with an overall capacity of 272 tonnes/day. • Elaborated the significance of both dry and wet continuous digester systems. • Setting-up a compressed biogas plants requires high investment and operational cost. • Potential market for bio-fuels and bio-fertilizer needs to be explored in India. • Existing financial assistantship and subsidiary schemes need transformation. [ABSTRACT FROM AUTHOR]

The paper presents a novel thermodynamic modeling approach of a pilot solar biomass system for bio-methane energy production and wastewater treatment by creation of two packages (STSB and MHPB) modeling platform under TRNsys studio software. Indeed, several newly developed mathematical schemes using the communicating elements: a new Multi-stage air to water Heat Pump, a new Vacuum Tube solar Collector (VTC), thermodynamic storage, and a biogas reactor) have been validated by experiment. The work presents and discusses two scenarios (packages), the first one –STSB- concerns the pilot solar-biomass system, and uses only renewable energy for the bio-methane production by anaerobic digestion mechanism under the mesophilic conditions (±35 °C to ±42 °C), The second scenario consists of a modeling Multi-stage Heat Pump Biomass reactor (MHPB). The packages developed have been tested for industrial case study. A validation process of two scenarios with experimental tests of a 500 L reactor -for the biomass of the cardboard paper-proves a good agreement, where the errors band is about 1% for STSB and 1.5% for the MHPB package. The biogas reactor treats about 900 (m3/year) liquid biomass (3 m3/day). The prediction results indicate that the biogas production attaint 51 (m3) per year. According to the biogas composition analysis, the bio-methane represents 74%, leading to prediction results of 38 (m3) per year of bio-methane for the case study.. Further, the extended results from the modeling packages platform indicate that for this installation type of 700 m3, the bio-methane (CH4) production is estimated of 52 836 (m3) per year, representing 64% of the total fuel consumption for the current case of cardboard recycling and packaging company. • Two free packages (STSB and MHPB) was developed for simulation the solar biogas process. • An experimental validation process of the two packages proves a good agreement of less than 1% for STSB and 1.5% for MHPB. • The reliability of the two packages was demonstrated under the climatic conditions input of 1 min as a time step over a complete one year. • The solar bio-methane reactor unit achieved a satisfactory annual thermal efficiency of 58% for all considering cases and 42% as an efficiency conversion of biogas production. [ABSTRACT FROM AUTHOR]

Abstract The rapid development of remote sensing (RS) technology enables an increased usage of high - resolution, spatial, temporal or spectral, data to extract vegetation information, improve model parameters, and estimate energy crop biomass accurately. Five estimation methods developing with RS information for energy crop biomass are summarized in this paper. Firstly, the statistical analysis with vegetation index can be regarded as the commonest method. But it is faulted for the deficiency of sample data and the vulnerability to the influence of many factors such as cloudy days. Secondly, the longer wavelength makes SAR information popular for crop biomass estimation. But many limitations lead to measurement uncertainty and bring about poor classification. Thirdly, NPP can directly reflect accumulated biomass production through photosynthesis and measure the consequences caused by climate change and human activities. But, actual LUE, the results of environmental stresses such as light intensity, temperature, water, and nutrients, is usually considered as a constant. Fourthly, crop height information is vitally important for biomass estimation. Yet the corresponding application is often subject to many factors e.g. crop variety, growth period, and farmland management practices limits. Lastly, the most promising approach lies in the possibility of assimilating state variables from RS data into CGMs. And the advent of latest instruments with better characteristics offer a unique chance to overcome current limitations. In the end, the main challenges and opportunities for energy crop biomass estimation using RS information in the future are listed. Highlights • Increasingly, remote sensing data is being used to estimate energy crops biomass. • Five estimation methods developing with remote sensing information are summarized. • Each estimation method has the strengths and weakness. • As the commonest method, the statistical analysis with VI has obvious drawbacks. • The most promising approach is to assimilate state variables from RS data into CGMs. [ABSTRACT FROM AUTHOR]

Abstract Renewable energy is expected to gain a larger share in the Indonesian energy mix by 2025. Biogas has not only the potential to contribute significantly to the country's renewable energy targets by mid-century, but also to provide a series of co-benefits to improve wellbeing of vulnerable rural communities. The challenge is to find pathways for biogas to overcome well-established technologies and practices in the current heavily fossil fuel based energy system. This paper focused on household-level biogas development in Bali, Indonesia, critically analysing four domestic biogas programmes that are currently under implementation. For our analysis, we adopted an integrated approach combining the multi-level perspective framework with a system-mapping exercise. Moreover, a series of semi-structured interviews as well as an interactive workshop was conducted which allowed us to place multiple stakeholder perspectives and experiences at the heart of the analysis to look at factors beyond the micro-system of the technology, and understand the broader socio-institutional context. Our analysis of enabling and hindering factors to biogas expansion identified opportunities for improving the design and implementation of policy, finance and technology measures. These findings are relevant not only for the Indonesian context, but also for other developing countries that are increasingly investing in transitioning to low-carbon energy futures. Highlights • Barriers to biogas adoption mainly found in policy sector, access to finance and capacity building. • Overcoming barriers is possible by improving steps in market chain and with right policies. • Focusing on co-benefits, creating ownership and build capacity amongst adopters will be crucial. [ABSTRACT FROM AUTHOR]

Abstract Energy access in Sub-Saharan Africa (SSA) remains a challenging issue at the midway point to the United Nations' development goals. From the perspective of energy efficiency and diversification of power-generation sources, this paper investigates the capacity of the wood-processing industry to contribute to the decentralised power generation by performing a techno-economic analysis of the use of wood residues for cogeneration. Using a survey performed in Cameroon as a case study, a biomass-fuelled cogeneration scheme and a model analysing its viability are proposed for the specific context of SSA. A sensitivity analysis indicates for a given process efficiency of the industry, the attractiveness of cogeneration as the processing capacity and feed-in tariffs of electricity increase. More specifically, the threshold of feed-in tariffs ensuring the economic viability of CHP in the sub-region is estimated at $0.15 per kWh for mills where the output capacities of sawn timber products are of 5000 cubic metre per annum and more. The power-generation potential from the primary processing of timbers in the sub-region is about 388 kWh per cubic metre of sawn wood, while the energy intensity of the sawing process is estimated at 132 kWh per cubic metre. Therefore, the industry can generate up to 2472 GWh of electricity in the three sub-regions of East, West and Central Africa if a total of US$ 2.5 billion is invested, allowing a substantial increase of 1% of the current electricity-generation capacity for the geographic location which has the most important forestry resources on the continent. Highlights • Wood-processing residues can contribute significantly to the distributed power generation in African forestry regions. • Energy patterns and the biomass feedstocks from wood-processing industries in Sub-Saharan Africa is comprehensively analysed. • The condensing-extraction steam turbine appears to be the most suitable technology for wood-fired CHP in Sub-Saharan Africa. • A model analysing the viability of industrial wood-fired CHP in the particular context of Sub-Saharan Africa is provided. • Key barriers to the development of waste-wood-fuelled CHP in Sub-Saharan Africa are identified. [ABSTRACT FROM AUTHOR]

Due to its abundance, wood is the pre-eminent lignocellulosic raw material for a sustainable bioeconomy based society. Wood is widely used as fuel, construction material, and raw material in cellulose and lignocellulose based products. Besides the established uses of wood powder, like co-firing with coal and biofuel production, there are also novel uses and process applications, e.g., advanced wood-plastic composites and biochemical production are emerging for which the pulverization or fine grinding of wood is an essential pre-treatment step. Due to the tenacious nature of the wood matrix, size reduction is an energy intensive process and thermal or chemical pre-treatment may be needed to improve economy. This paper provides a broad overview of the fine grinding of wood. First, wood breakage mechanisms and the mechanisms of size reduction are presented, followed by fine grinding techniques and wood pre-treatment methods. A comparison of the specific energy consumption of wood fine grinding in both a gaseous and liquid environment is illustrated. Additionally, examples are given of the role played by pre-treatment methods in decreasing energy consumption. The particle aspect ratio is discussed briefly. Finally, the use and requirements of wood powders in various applications are discussed. [ABSTRACT FROM AUTHOR]

The growing economic importance of the biomass-for-bioenergy in Europe motivates research on biomass supply chain design and planning. The temporally and geographically fragmented availability of woody biomass makes it particularly relevant to find cost-effective solutions for biomass production, storage and transportation up to the consumption facility. This paper addresses tactical decisions related with optimal allocation of wood chips from forest residues at forest sites to terminals and power plants. The emphasis is on a “hot-system” with synchronized chipping and chips transportation at the roadside. Thus, decisions related with the assignment of chippers to forest sites are also considered. We extend existing studies by considering the impact of the wood chips energy content variation in the logistics planning. This is a key issue in biomass-for-bioenergy supply chains. The higher the moisture content of wood chips, the lower its net caloric value and therefore, a larger amount of chips is needed to meet the contracted demand. We propose a Mixed Integer Programming (MIP) model to solve this problem to optimality. Results of applying the model in a biomass supply chain case in Finland are presented. Results suggest that a 20% improvement in the supplier profit can be obtained with the proposed approach when compared with a baseline situation that relies on empirical estimates for a fixed and known moisture content in the end of an obliged storage age. [ABSTRACT FROM AUTHOR]

Several recent life cycle assessments (LCA) of biomass densification have been carried out. This paper reviews data from 19 sources with 48 case scenarios to assess the current status of LCA of biomass densification. It describes the specific units in a reference “gate-to-gate” LCA in relation to the existing studies, and summarises key differences between them. Finally, it provides a qualitative analysis of the associated sources of uncertainty. Existing LCA studies of biomass densification were found to provide insufficient and inconsistent information for full transparency and comparability, due to different choices in system boundary, functional unit, allocation procedure, densification technology and biomass residues. Most of the reviewed studies attributed most of the energy use and greenhouse gas (GHG) emissions to transportation, drying and densification. The energy and GHG emissions of the gate-to-gate densification system were highly sensitive to the technology, feed material used in densification and scale of production. Apart from one study with zero energy consumption as a result of the use of manual operations, the normalised values of energy consumption for the reviewed studies ranged from 20 to 900 kJ MJ −1 . Neglecting three outlier values, GHG emissions as mass of CO 2 -eq for the reviewed studies ranged from 600 t MJ −1 to 50 g MJ −1 . Similar variations in result and outlier cases have beesn reported for other bioenergy processes, by other authors. Assuming that the biggest impact of densification processes is on transport fuel use, and based on 5 studies that reported densification ratios, the net energy and GHG emissions savings resulting from densification ranged from 200 to 1000 kJ MJ −1 and 9 to 50 CO 2 -eq (g MJ −1 ), respectively. On this basis, it can be concluded that biomass densification is a worthwhile addition to the biomass energy conversion system. There is a need for more transparent reporting and analysis of uncertainty in the modelling, to better understand the wide variation in outcomes. [ABSTRACT FROM AUTHOR]

Worldwide environmental policies demand each time more biofuel consumption and less emission. In this context, this work presents a 2G ethanol study as a mean to increase bioethanol production and availability. Currently, technologies use sugarcane bagasse for lignocellulosic ethanol production, which may unbalance the ethanol and sugar mill energy matrix, since bagasse and straw are the main fuel for power and steam generation. A possible solution is using biogas produced from vinasse biodigestion as a fuel instead of using biomass, enabling to shift a fraction of the sugarcane bagasse to 2G ethanol production and, at the same time, keeping power and steam production constant. This paper assesses that energy shift by analyzing ten different scenarios for power generation, comparing the amount of bagasse shifted, the increase in straw consumption, the increase in ethanol production and the reduction of environmental emissions in each scenario. The results show that, at least from the technical and environmental perspective, a combined cycle operating at a high pressure is the best alternative. It is possible to shift from 56.5% to 100% of the available bagasse using the combined cycle technology, which is also followed by an increase in straw consumption. In addition to that, the ethanol availability increase ranges from 28.5 to 50.4%. Moreover, the organic load disposal to the ground also decreases more than 90% compared to the conventional process due to the introduction of vinasse biodigestion. [ABSTRACT FROM AUTHOR]

This paper makes projections of the theoretical and technical potentials of bioenergy supply for 2050. The projections consider changes in available land for bioenergy and food for the global demand and advancements in yield, productivity, expansion of bio-waste recovery, and energy conversion. We present a literature review on projections. We introduced a novel logical and transparent forecasting model. Three future scenarios were established: business as usual (BUS), optimistic trends (OPT), and full adaptation response (FAR). The projection is carried out based on four adjusting factors. An uncertainty analysis was carry-out based on a Monte-Carlo method. Projections of bioenergy production in 2050 were compared with other projections in the literature. The FAR scenario showed that it would be possible to produce twenty-one times the current primary bioenergy supply and to even supply all global primary energy demand in 2050, mostly by energy crops. The assumptions adopted for the BUS and OPT scenarios make their projections more likely. Therefore, the contribution of bioenergy in the global energy matrix is expected to be between 64 and 313 EJ (7.5%–37%) in 2050. There would be a significant change in the composition of the bioenergy supply from today's mostly firewood to energy crops and biowastes. The technical potential for fuel and electric power mostly follow the supply trends for primary bioenergy (theoretical). The potential avoided greenhouse emissions are estimated. The heuristics and the level of transparency of the novel model will allow adjustments and exploration of other scenarios as time passes. • Novel model for projections of the potential of global primary bioenergy supply. • Bioenergy supply potential is shown for 11 different groups of biomass. • Global primary bioenergy supply could increase up to 6 times by 2050 (37% of demand). • Full adaptation response scenario could meet 100% of the global energy demand. • Bioenergy can play a major role in the global energy supply. [Display omitted] [ABSTRACT FROM AUTHOR]

The paper discusses alternatives for biofuel-based district heating using simulation analysis in a real-life case example. First, the paper illustrates the current supply chain structure of forest chips from harvest to the heat energy plant. Usually the chips are naturally dried, chipped on the roadside and transported to the heating plant based on the orders. Second, the study demonstrates how a regional bioenergy system could be developed with the help of a simulation model for evaluating the feasibility of different wood fuel supply chain options. The model mimics a real-life example of an industrial area in a small Finnish municipality planning to invest in a CHP plant. The results show that the investment in a CHP plant and use of artificially dried wood fuel can be profitable in the circumstances where local demand exists for heat energy. The simulation-based vision can be compared with the presently dominant concept of highly decentralized supply chains for wood chips that is widely used among energy suppliers. However, to optimize the transportation costs and the moisture content of the chips changes are needed in the supply chain processes and structure. The results of this study are useable for practical decision-making and offer useful ideas for continuing research on alternative ways to produce energy wood biomass in the future. • Supply chain of forest chips in Finland is presented. • A real-life case of an industrial area demostrating how a regional bioenergy system could be developed is presenting. • The simulation model created minics the real-life case. • Feasibility of different wood fuel supplu chain options are discussed. [ABSTRACT FROM AUTHOR]

High initial viscosity in the high-solids (>15% (w/v)) enzymatic hydrolysis of lignocellulose is problematic especially in stirred tank reactor concepts. One potential way to avoid the high viscosity is the fed-batch feeding of lignocellulosic material to the reactor. In the current study the hydrolysis of filter paper with final concentration of 19.1% (w/w) was evaluated with different fed-batch procedures. Feeding was based on visual observation, stepwise feeding and the power requirement of the stirrer motor. All the fed-batch procedures resulted in similar yields within 30 h (47–49%) which were higher than with the batch process in similar reactor (38%). However, the mixing behavior was superior in the power based feeding as the instantaneous power of the stirrer motor was kept lower (<10 W) than in other fed-batch procedures (>20 W). The power controlled procedure was further evaluated with different enzyme doses, tip speeds and the power levels of substrate feed. Further study showed that the power controlled feeding is applicable also to other hydrolysis and mixing conditions if power levels of substrate feed are set correctly. Higher (15 FPU/g) enzyme dose caused shorter feeding time (3.0 ± 0.5 h) and lower energy consumption during the feeding period (14 ± 3 Wh) compared with lower (5 FPU/g) enzyme dose (7.0 ± 1.3 h and 33 ± 5 Wh, respectively). The tip speed and the power level of substrate feed had fewer effect on these factors. The performance of the hydrolysis process can thus be enhanced by the substrate feed controlled by the power of the stirrer motor. [ABSTRACT FROM AUTHOR]

The significant growth aviation has been observing is increasing the sector's pressure on the environment; in the EU28, passengers travelling by air in 2016 increased of 5.9% compared to 2015. The aviation industry voluntarily committed to significant aspirational goals, and identified bio-based aviation fuels as a potential means to improve its environmental performance. Despite of that, the market penetration of aviation biofuels in EU28 is almost negligible. In this paper, an assessment of the likely aviation biofuels demand has been carried out, under a baseline scenario of increasing total fuel consumption of +3% for 2016–2020 and + 3.5% up to 2030; the CO 2 intensity of this growth has been calculated accordingly. Europe is a World leader in biofuel technologies; the current potential aviation biofuels is based on the HVO/HEFA technology, and the upper limit of the installed capacity can be considered approximately 2.4 Mt y−1. Nevertheless, lower production volumes can be expected as production plants are today optimized for road fuel production, not aviation. By 2025 the situation may change, with a total production capacity of 3.5 Mt y−1, and with an average potential production for aviation biofuels ranging 0.5–2 Mt y−1. The paper shows that even if today's EU nominal capacity appears large enough to support the expected aviation biofuels demand, other bottlenecks may limit the real market uptake: availability of sustainable feedstocks, competition with demand for road transport sector, etc. For this reason, a comparison of the cost for CO 2 saving of other potential solutions to mitigate aviation's climate impact has also been carried out. • The paper estimates the current EU28 nominal HVO/HEFA installed capacity, in about 2.3 Mt y−1. • A lower value can be expected for aviation biofuels (355 kt y−1), as production is today optimized for road biofuels. • Biofuels to meet aviation carbon neutral growth would account for 16% of the current EU total biofuel demand. • Availability of sustainable feedstock may constitute a bottleneck for the sector. • The costs comparison for CO 2 saving, between biofuel and ETS allowance, seems to favour the latter. [ABSTRACT FROM AUTHOR]

Biomass gasification based building cooling, heating, and power (BCHP) system is an effective distributed energy system to improve the utilization of biomass resources. This paper proposes a combined methodology of optimization method and life cycle inventory (LCI) for the biomass gasification based BCHP system. The life cycle models including biomass planting, biomass collection-storage-transportation, BCHP plant construction and operation, and BCHP plant demolition and recycle, are constructed to obtain economic cost, energy consumption and CO2 emission in the whole service-life. Then, the optimization model for the biomass BCHP system including variables, objective function and solution method are presented. Finally, a biomass BCHP case in Harbin, China, is optimized under different optimization objectives, the life-cycle performances including cost, energy and CO2 emission are obtained and the grey incidence approach is employed to evaluate their comprehensive performances of the biomass BCHP schemes. The results indicate that the life-cycle cost, energy efficiency and CO2 emission of the biomass BCHP system are about 41.9 $ MWh-1, 41% and 59.60 kg MWh-1 respectively. The optimized biomass BCHP configuration to minimize the life-cycle cost is the best scheme to achieve comprehensive benefit including cost, energy consumption, renewable energy ratio, steel consumption, and CO2 emission. [ABSTRACT FROM AUTHOR]

The demand for renewable energy is increasing due to increasing energy consumption and global warming associated with increasing use of fossil fuels. Hydrogen gas is considered as a good energy carrier due to its high energy content. Biomass (e.g. agricultural and forestry residues, food industry wastes, and energy crops) is amenable to dark fermentative hydrogen production. However, lignocellulosic materials require pretreatment and/or hydrolysis prior to dark fermentation. This paper reviews potential biomass sources for hydrogen fermentation as well as the effects of different pretreatment and hydrolysis methods on sugar yields as well as hydrogen yields from hydrolyzates. The effects of process parameters on dark fermentative hydrogen production from lignocellulosic hydrolyzates are also discussed. [ABSTRACT FROM AUTHOR]

Supercritical water oxidation (SCWO) is an effective, promising technology for destroying almost all kinds of organic waste with the advantage of high removal efficiency and low residence time, and without producing pollutant byproduct. The chemical energy of organic pollutants can be considered as an emerging renewable energy source. As a high-temperature and pressure process, an immense energy demand is required in the pressurization and preheating sections. On the other side, the reactor effluent has a great potential for energy recovery because of the great amount of heat released during the SCWO reaction combined with the previous energy input. Thus, SCWO is not only an organic waste treatment process but also an energy conversion and utilization system. The application of SCWO has been extended to the clean, efficient utilization of low-quality fuels such as high-sulfur coal, heavy oils, and biomass instead of conventional combustion, hydrothermal spallation drilling in geothermal energy production, and heavy oil recovery. However, energy consumption cost is still rather high in the actual process due to insufficient equipment performance, unreasonable energy system integration, and selection of an anti-corrosion and salt plugging reactor. Thus, a systematic, in-depth analysis on energy conversion and utilization in SCWO is conducted for the first time in the paper. The mechanism of exergy destruction analyses indicates that reducing enthalpy change and energy level difference are critical to reducing energy consumption. Suggestions on improving energy efficiency are proposed in the preheating stage, chemical exergy release, and reactor design. [Display omitted] • Energy conversion and utilization in each stage of an SCWO system are analyzed. • Research methods and evaluation parameters for energy utilization are summarized. • Main factors affecting energy efficiency are summarized and analyzed. • The mechanism of exergy destruction is analyzed to reduce energy consumption. • Suggestions on improving energy efficiency are proposed. [ABSTRACT FROM AUTHOR]

The link between energy and climate change is fundamental - energy accounting for two-thirds of global greenhouse gas emissions. Of all countries, those of the Arabian Peninsula are synonymous with energy and the supply and use of fossil fuels. However driven by commitments to international climate change agreements the Gulf Cooperation Council (GCC) countries have been developing alternative energy strategies with targets for renewables. This paper presents the outputs of biomass resource modelling analyses that identify bioenergy opportunities across the region. Municipal wastes are found to represent a leading opportunity for bioenergy with a combined 19.35 Mtpa of resource across the GCC currently being sent to landfill that could otherwise be used for energy. The research finds that up to 22.5% of GCC country electricity could be generated from bioenergy technologies fuelled by indigenous biomass resources. Interviews were undertaken with Director-level GCC individuals from industry and government and a survey was facilitated to gain an understanding of perceptions of bioenergy and the potential barriers to its greater deployment. There was majority support for renewable technologies and for bioenergy, however a majority of respondents were found to be 'not willing' or 'unsure' when asked if they would be willing to take any individual actions such as recycling to support bioenergy schemes. High availability of cheap fossil fuels, stimulated by fossil fuel subsidies is identified as the greatest barrier to renewables. The GCC's commitment to international climate and sustainability targets represents an opportunity to develop a strategy to phase out fossil fuels. • Focus GCC Countries: Bahrain, Kuwait, Oman, Qatar, Saudi Arabia & the UAE • 19.35 Mtpa of MSW resource currently sent to landfill, could be used for bioenergy • 1.68 Mtpa of crops residues & 25.52 Mtpa of animal wastes could be used for bioenergy • Bioenergy from indigenous resources could balance up to 22.5% of power. • Expert stakeholder & GCC public supportive of greater deployment of bioenergy [ABSTRACT FROM AUTHOR]

This paper focuses on a new configuration of biomass gasification based cascaded ammonia synthesis and proposes two different configurations of ammonia synthesis system using the Stoichiometric and Gibbs reactors in the Aspen Plus V11. A new heat recovery technique from biomass gasification using syngas cooling is also proposed in this study. The proposed configuration comprises of a biomass gasifier, a heat recovery unit for syngas cooling, a combined cycle, water gas shift reactor system (WGSRS), pressure swing adsorption (PSA) and ammonia production unit. The ammonia based carbon-capturing system is incorporated to ultimately capture the CO 2 emissions. The sensitivity analyses are conducted on each significant subsystem employed in the proposed configuration. The results obtained from the Gibbs reactors show that pressure has a positive effect while very high-temperature effects negative on the ammonia synthesis. The results also reveal that the cascaded ammonia synthesis offers high ammonia conversion rates. The designed system produces 21.9 kmol/h of ammonia and 3405 kW electrical power. The results obtained from the present sensitivity analysis are further presented and discussed. • New configuration of biomass gasification based cascaded NH 3 synthesis is proposed. • New heat recovery technique is proposed using the syngas cooling. • The designed system produces 21.9 kmol/h of ammonia and 3405 kW electrical power. • Overall exergy and energy efficiencies are found to 44.2% and 42.4% respectively. [ABSTRACT FROM AUTHOR]

The present paper aimed to develop a simple transient mathematical model to analyze the centrifugal separation of microalgae particles dispersed in a culture medium, considering a two-phase mixture: a dispersed (microalgae) and a continuous (culture medium) phase. Mass balances were written for the dispersed phase in the suspension zone for the interface between suspension and sediment, and the mixture, resulting in an EDO system. The mathematical model was adjusted according to experimental data and, thus, it was possible to predict the volume fraction profiles of microalgae in the suspension, the fraction of residual particles in the clarified, and the sediment thickness. It can be predicted that the capture efficiency was 97.5%. The optimization showed that rotation should be higher, while the mass flow rate should be lower than those originally used in the centrifuge operation, resulting in capture efficiencies of 98.5% and 97.7%, respectively. Geometry optimization revealed that the centrifuge basket must be higher and have a diameter smaller than that of the original geometry, whose capture efficiency was 97.8%. Finally, for all optimized cases, the values of the energy efficiency indicator were lower than the value for the original case, reaching a reduction of up to 21.9% of the energy required in the process for each dollar of profit. • A mathematical model was developed to predict microalgae fraction and sediment thickness. • The mathematical model was adjusted according to experimental data. • Geometric and operational parameters in order to maximize the profit were investigated. [ABSTRACT FROM AUTHOR]

There is consensus that the use of renewable energy must be expanded. More and more restrictions on the use of fossil derived fuels may open the way for an increased consumption of biomass event those so far not perceived as feasible, such some biomass residue. Energy derived from biomass residues may provide even more benefits because it may replace other sources of higher-grade energy while providing proper destination for residues. Biomass from pruning residue has been overlooked as an energy resource due to many limitations. This paper addresses the issue and the means for energy valuation of pruning residues while provides final destination for them. It presents a framework to overcome most of today's challenges across the world. A case study was carried out to determine the main constraints and how they can influence the decision-making process. The variety of urban pruning residues and their rate of generation, handling, storage, logistics, economic and environmental issues, institutional regulations for a small city in Southern Brazil were taken into consideration in the analysis. Pruning residues were sampled in the field, then handled, shredded, dried, specified, stored and burnt in a concurrent woodburning furnace for testing. The diagnostics of the constraints and the lab tests were summarized and organized in a framework that aimed to assess the energy valuation of pruning residues. Results show that with proper assessment tools, projects, biomass analyses and burning technology energy valuation of pruning residues can be feasible. • Energy valuation of biomass pruning residues is feasible given proper conditions. • A novel assessment framework provides routes to overcome most of today's challenges. • A case study of energy valuation of urban pruning biomass residue in Brazil showed feasible to generate 1 to 1.5 MWe. • Information and data of bulk density, moisture content, heating value, of residues of five urban tree species. • Estimate of opportunity costs of disposal of biomass pruning residues in landfills. [ABSTRACT FROM AUTHOR]

The trend towards decentralised electricity generation and combined heat and power (CHP) is continuously increasing. The transition towards a decentralised power system relies on small-scale and often intermittent generation, bringing new challenges such as matching the demand with supply. A possible solution is the use of renewable energy technologies able to accommodate the demand profile, such as biomass gasification. However, operation at part-load is required and thus limiting the gasification performance efficiency. In this paper, a novel experimental assessment and performance results of a biomass gasification system are presented, consisting on the evaluation of the system performance for steady-state conditions at different loads. Gasifier performance at steady-state conditions showed relatively stable reduction and throat temperatures, with average values of about 729 °C and 915 °C, respectively. These high temperatures assure a producer gas LHV of about 5.5 MJ/kg. Decreasing the gas flow rate resulted in a decrease of both reduction and throat temperatures. Nonetheless, the gas LHV increased until 62.5% where a maximum of about 6 MJ/kg was measured. Concerning the equivalence ratio, it decreased with load, attaining a minimum value at 80%, where the best cold gas efficiency results were found (74%). Image 1 • Novel assessment of a small-scale downdraft gasifier at part-load operation. • Enhancement of cold gas efficiency and equivalence ratio at part-load. • Enhancement of lower heating value at part-load. • Assessment of gasification temperatures at part-load. • A detailed description of experimental gasification performance methodology. [ABSTRACT FROM AUTHOR]

This paper presents a method using an artificial neural network for creating an optimal model of energy consumption in wastewater treatment plant (WWTP) using activated sludge process. The advantage of this method is the use data usually measured in most of WWTP to optimize the energy consumption of the biological process. This method consists of selecting the data that represent the best energy consumption using different performance criteria then use this data to train a deep neural network. The procedure of selection is divided into two parts, in the first selection we selected the data that respect the environmental standards, and in the second part we selected the data with optimal energy consumption using different pollution indicators, and this data was used to train a deep neural network, finally the best model was used to estimate the energy savings on the data not selected. The model showed good results with a coefficient of determination that varies between 90% and 92% in training period and 74%–82% in testing period, the application of the best model on the data not selected showed a gain in energy for the most of the data. • High values of performance criteria in training and testing period • Determination of three classes of energy consumption: Underconsumption, overconsumption and optimal consumption. • Determination of warning limits of overconsumption of energy. [ABSTRACT FROM AUTHOR]

Abstract Chipping weighs heavily on the total delivered cost of wood fuel, which calls for accurate chipping cost estimates. Chipper repair and maintenance cost is perhaps the most obscure among the figures required for a reliable estimate of chipping cost. To clarify this issue, the authors examined the long-term repair and maintenance records for 51 wood chippers operated by 48 chipping service contractors. Repair and maintenance represented between 1.5% and 29% of total chipping cost, inclusive of fuel and labour (mean = 14%). The ratio between total accumulated repair (TAR) cost and machine price averaged 32% and varied with total use. The relationship between total use and TAR to price ratio was explored through regression analysis, which produced a very strong model (R2 = 0.8). This model predicts a TAR to price ratio of 0.64 at 10000 h, with no significant differences between tractor-driven and independent-engine machines. While the coefficients are different, the structure of this model offers a good match with the repair and maintenance cost models developed for farm tractors and other agricultural machinery. A second model was developed for estimating repair and maintenance cost as a function of fuel consumption. The study also provides reference figures for the contribution of labour cost to total maintenance cost. Farm tractors incur more repairs than preventive maintenance, contrary to the other dedicated components of the chipping operation, where preventive maintenance represents most of maintenance cost. Forestry users should make allowance for the lower structural strength of tractors and select large models. Highlights • Long-term maintenance records were obtained for 51 wood chippers. • Maintenance is 14% of chipping cost on average, and ranges between 1.5 and 29%. • At 10000 h, total accumulated repair (TAR) cost amounted to 60% of machine price. • A model was developed for predicting TAR as a function of total use. • Maintenance was also estimated as a function of fuel consumption. [ABSTRACT FROM AUTHOR]

Abstract Currently different trade units are used throughout the forest energy supply chain in Sweden: chipping contractors are paid per m3 chipped volume, dry metric tonnes or MWh, hauliers per raw tonnes or m3 chipped volume and the company supplying the chips to the heating plant most often per delivered MWh. This introduces business risks for all market players, and affects studies of chipping equipment. Lately, Skogforsk has used oven dry tonnes, but stakeholders that measure chips in other units want results to be presented in these units as well. To raise awareness about output unit selection and its effect on productivity and fuel consumption studies, Bruks 806 chippers were studied when chipping spruce and beech residues. Results show that the selection of output unit affects the capacity of detecting treatment differences and the direction of such differences. Chipping productivity based on effective chipping time was higher for spruce residues when calculated using chipped volume, and for beech when calculated using raw weight. Similar trends were found for fuel consumption per product unit. As both feedstock characteristics and output measurement unit selection affects study results, a proper experimental design to control these effects is important. In many cases it is a matter of keeping feedstock constant during comparisons of machines/treatments. Care is needed when using chipped volume, as chipper settings may influence chip bulk density and thus chip volume. The use of different units throughout the supply chain reduces transparency and increases the risk for sub-optimal decisions. Highlights • Output unit affects the possibility to detect differences in chipper efficiency. • The direction of treatment differences may depend on the choice of output unit. • Output unit choice is an issue when comparing feedstocks or published results. • Effects of output unit choice can be controlled by a proper experimental design. [ABSTRACT FROM AUTHOR]

Experiments made with a model helical chipper have shown that the infeed angle has a huge impact on chip quality parameters. Furthermore, it could be pointed out that the self feeding mechanism of the helical chipper was impeded with larger infeed angles and finally failed. This situation led to the hypothesis that the infeed angle must have an impact on power requirement during chipping. In the present investigation this conclusion was tested. Standardized preformed test rods were chipped with a helical chipper at seven different infeed angles while torque, rotational speed and chipping time were recorded. The experimentation was done using poplar wood with different moisture content. Based on the measurements power requirement and energy consumed was calculated for each test series. The results of the experiments show that power requirement and energy consumed are decreasing with increasing infeed angle. The results seem to be extraordinary since increasing infeed angles lead to decreasing chip sizes being produced. Based on theoretical deliberations and experimental data it can be assumed that besides the anisotropic character of wood geometrical settings of helical chipping could be a reason for the experimental findings. But, because the chipping time is also dependent on the infeed angle there still must be other reasons concerning the occurring forces during helical chipping, too. For this reason there is a need to have a closer look onto the different forces occurring during helical chipping. Against this background the Discrete Element Method (DEM) could be a simulation method for future research. [ABSTRACT FROM AUTHOR]

Abstract: The Authors surveyed 6 industrial chipping operations for a whole work year, collecting data about machine usage, product output, fuel consumption and chipper knife wear. Despite the challenging work conditions offered by mountain operations, industrial chipping contractors manage to achieve a high machine use, ranging from 500 to over 2,500 h year−1. Product output varies between 18,000 and over 120,000 m3 loose chips per year. In order to acquire enough jobs, operators may travel between 1,500 to over 20,000 km in a year. Industrial chipping contractors adopt different operational strategies to achieve their production targets, and they equip accordingly. Some operators prefer to tap smaller local areas and opt for smaller tractor-powered chippers, which are less powerful and productive than larger independent-engine units, but cheaper and capable of negotiating low-standard forest roads. Others prefer to explore larger areas and achieve higher product outputs, and they opt for larger independent-engine chippers, often mounted on trucks. Long term productivity varies with machine type: tractor-powered units produce between 40 and 50 m3 loose chips per hour, whereas larger independent-engine chippers produce between 60 and 90 m3 loose chips per hour. Specific fuel consumption is about 0.5 L diesel per m3 loose chips, regardless of chipper type. A sharp knife set can process between 200 and 1,500 m3 loose chips before getting dull. Disposable knives last longer and are cheaper to manage than standard re-usable knives. [Copyright &y& Elsevier]