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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]

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]

Abstract: Malaysia has an abundance of energy resources, both renewable and non-renewable. The largest non-renewable energy resource found in Malaysia is oil, and second, is natural gas, primarily liquefied natural gas. The production and consumption of oil, gas and coal in Malaysia are given in this paper. The energy demand and supply by source are also shown in relation to the country’s fuel diversification policy. In order to reduce the overall dependence on a single source of energy, efforts were undertaken to encourage the utilization of renewable resources. Forest residue and oil palm biomass are found to be potentially of highest energy value and considered as the main renewable energy option for Malaysia. Palm oil and related products represent the second largest export of Malaysia. The total oil palm planted area in Malaysia has increased significantly in recent years. This paper gives a detailed representation of oil palm planted and produced together with its yield from the year 1976 onwards. The large amounts of available forest and palm oil residues resulting from the harvest can be utilized for energy generation and other by-products in a manner that also addresses environmental concerns related to current waste disposal methods. [Copyright &y& Elsevier]

Abstract: The life cycle greenhouse gas (GHG) and fossil fuel benefits of black liquor recovery are analyzed. These benefits are due to the production of energy that can be used in the pulping process or sold, and the recovery of the pulping chemicals that would otherwise need to be produced from other resources. The fossil GHG emissions and non-renewable energy consumption of using black liquor in the kraft recovery system are approximately 90% lower than those for a comparable fossil fuel-based system. Across all scenarios, the systems relying on black liquor solids achieve a median reduction of approximately 140 kg CO2 eq./GJ of energy produced, compared to the systems relying on fossil fuels to provide the same energy and pulping chemical production functions. The benefits attributable to the recovery of pulping chemicals vary from 44% to 75% of the total benefit. Applied to the total production of kraft pulp in the U.S., the avoided emissions are equivalent to the total Scopes 1 and 2 emissions from the entire U.S. forest products industry. These results do not depend on the accounting method for biogenic carbon (because biogenic CO2 emissions are the same for the systems compared) and the results are valid across a range of assumptions about the displaced fossil fuel, the GHG-intensity of the electricity grid, the fossil fuels used in the lime kiln, and the level of cogeneration at pulp and paper mills. The benefits occur without affecting the amount of wood harvested or the amount of chemical pulp produced. [Copyright &y& Elsevier]

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: The authors tested a 409 kW forager turned into an industrial chipper through a special conversion kit. Conversion was temporary, and the forager could be returned to its original occupation with one day of work. The converted forager proved as effective as a dedicated chipper of the same power. Net chipping productivity varied between 25 and 33 green t h−1. Productivity was highest with poplar tops and lowest with pine tops. Fuel consumption ranged from 1.6 to 1.8 l green t−1. Fuel consumption did not change with tree species, but increased significantly with knife wear. Temporary conversion allowed a better depreciation of the invested capital and resulted in a 25% reduction of unit chipping cost. The converted forager proved an ideal solution wherever the production of wood chips was a complementary business within the scope of a larger agricultural economy. In technical terms, this machine offered the combined advantages of road-capability and good off-road mobility, allowing low-cost independent relocation and effective in-field chipping. [Copyright &y& Elsevier]

Abstract: A commercial drum chipper was fed alternately and piecewise with poplar stems and poplar tops, in order to determine the effect of piece size and tree part on machine performance. Chipping stems required most of the available power (231 kW) delivered by the tractor, whereas chipping tops took about half that much. However, productivity was twice as high with stems, compared to tops (i.e. 25 and 11 t h−1 of oven dry wood, respectively). As a consequence, specific fuel consumption per unit product was 15% lower with stems, compared to tops – i.e. 0.61 and 0.72 L m−3, respectively. Mean feeding speed was 0.37 m s−1 for stems and 0.41 m s−1 for tops, but the difference was not significant (p = 0.1677). Productivity and fuel consumption were strongly related to piece size, but tree part had its own additional effect, independent from size and possibly related to form. When chipping tops it is advisable to feed more pieces at a time, in order to partly compensate for the effect of piece size. Operators expecting to chip primarily small-size materials may acquire special chipper versions with wider drums and additional side rollers, for smoother mass feeding. [Copyright &y& Elsevier]

Abstract: Lignocellulosic biomass, particularly agricultural and forestry residues, is becoming a potential renewable energy and products source. Lignocellulosic biomass processing technologies include a primary separation of its main constituents, cellulose, hemicelluloses and lignin, as well as further treatment and processing to obtain different platform chemicals to design consistently structured compounds as chemical building blocks. The economic competitiveness of the obtained products is highly dependent on the separation and purification technologies used and the process energetic efficiency. For this proposal, process simulation tools are very useful to design a competitive and effective biorefinery scheme. In the present work, the energetic and economical efficiencies of two biorefinery processes, soda and organosolv-ethanol systems, were analyzed using the simulation software Aspen Plus®. The process design consisted of several units (reaction, solid fraction washing, products recovery and liquid fraction processing). Mass and energy balances were established and both systems were compared in terms of yield, solvents/reactants recovery and energy consumption. Aspen HX-Net software was used to analyze the process heat exchange network in order to improve energy consumptions. The development of rigorous simulations allowed to determine the economical feasibility of both biorefinery schemes, and to establish the most appropriate operation conditions for both processes. [ABSTRACT FROM AUTHOR]