Showing papers on "Biogas published in 2023"

Does anaerobic digestion improve environmental and economic benefits of sludge incineration in China? Insight from life-cycle perspective

Abstract: This study comprehensively compares the anaerobic digestion followed by incineration (ADI), and incineration without digestion (INC) routes based on energy balance, material flows, environmental impacts, emergy analysis (EA), and investment and operational (I&O) from life-cycle perspective. Traditional anaerobic digestion (AD) exhibits low AD efficiency and volatile solid (VS) content, and INC outperforms ADI in terms of environmental impacts and economic performance, whereas the ADI shows greater sustainability potential. With high total solids (TS), the AD energy consumption decreases significantly, and the energy gap between ADI and INC routes is expected to be eliminated at TS content of 7%. Furthermore, the higher AD efficiency tends to produce more biogas and decreases energy consumption and operational costs of thermal drying. According to the I&O and EA results, sludge with higher VS, that is, above 60%, exhibits better ecological and economic benefits, even though 65% extra capital investment is required for biogas equipment.

Development of the Biomethane Market in Europe

Abstract: The challenges related to climate policy and the energy crisis caused the search for alternative ways of obtaining energy, one of the essential tasks faced by scientists and political decision-makers. Recently, much attention has been paid to biomethane, which is perceived as a substitute for natural gas. Compared to the traditional combustion of biogas in cogeneration units (CHP), upgrading it to the form of biomethane can bring both environmental benefits (reduction in GHG emissions) and economic benefits (higher efficiency of energy use contained in biomass). The purpose of this review was a comprehensive assessment of the conditions and opportunities for developing the biomethane sector in the EU in the face of challenges generated by the energy and climate crisis. The article reviews the condition of the biomethane market in the European Union, focusing on such issues as biomethane production technologies, current and future supply and demand for biomethane, and biomethane production costs with particular emphasis on upgrading processes and financial support systems used in the EU countries. The review showed that the market situation in biomethane production has recently begun to change rapidly. However, the share of biomethane in meeting the needs for natural gas remains small. Moreover, the available expert studies indicate a significant development potential, which is desirable because of the need to increase energy security and environmental and economic reasons. However, this will require organizing the legal environment and creating a transparent system of incentives.

Anaerobic Co-Digestion of Pig Manure and Rice Straw: Optimization of Process Parameters for Enhancing Biogas Production and System Stability

Abstract: The objective of this study was to optimize the process parameters of the anaerobic co-digestion of pig manure and rice straw to maximize methane production and system stability. In this study, batch experiments were conducted with different mixing ratios of pig manure and rice straw (1:0, 1:1, 1:5, 1:10, and 0:1), total solid concentrations (6%, 8%, 10%, 12%, and 14%), and inoculum accounts (5%, 10%, 15%, 20%, and 25%). The results show that a 1:5 mixing ratio of pig manure to rice straw, a 12% total solid content, and a 15% inoculum account yielded biogas up to 553.79 mL/g VS, which was a result of co-digestion increasing the cooperative index (CPI > 1). Likewise, the evolution of the pH and VFAs indicated that the co-digestion system was well-buffered and not easily inhibited by acidification or ammonia nitrogen. Moreover, the results of the Gompertz model’s fitting showed that the cumulative methane production, delay period, effective methane production time, and methane production rate under optimal conditions were significantly superior compared to the other groups employed.

Optimizing the grass bio methanation in lab scale reactor utilizing response surface methodology

Abstract: Assessment of biogas production from Napier Grass (NG) in co-digestion with cattle dung (CD) was carried out in laboratory scale reactors and optimization using response surface methodology (RSM) and Box-Behnken design of the experiment. The effects of total alkalinity (TA), volatile solids (VS), pH, and volatile fatty acids (VFA) at three levels were investigated along with gas production. In this study, we determined the optimal ratio for biogas generation from NG and CD co-digestion. The three blending ratios were adopted as NG:CD (50:50), NG:CD (65:35), and NG:CD (75:25). The optimized result revealed that the highest generation of biogas was achieved at the blending ratio NG: CD (65:35) up to 0.4813 m3/kg VS. However, the significant value of R2 (0.9825) during RSM optimization highlighted that, the model might be effectively used to forecast the generation of biogas from the blending of CD and NG. The result shows that TA, VS, pH and VFA are essential for biogas production and the model algorithm could be applied extensively to estimate biogas generation from the co-blending of various organic biomasses. There is a good correlation between each parameter and the overall generation of biogas in the ANOVA results.

Review of microwave pyrolysis of sludge to produce high quality biogas: Multi-perspectives process optimization and critical issues proposal

Abstract: With the increasing depletion of fossil energy and the development of carbon neutral sustainable concept, the production of high-quality biogas from renewable biomass has important applications. Microwave pyrolysis technology, as a biomass conversion method with the high pyrolysis efficiency, good quality of biogas products and high energy utilization efficiency, has attracted wide attention. However, due to the key defects of microwave pyrolysis technology, it is still in the laboratory scale and has not been applied on a large scale. Therefore, in order to improve the application potential of microwave pyrolysis technology in biomass energy development, this work selects sludge as the representative of biomass, and summarizes 172 related research on the production of high-quality biogas by microwave pyrolysis sludge. In this review, the exploration of key influencing factors, insight into pyrolysis mechanisms from different perspectives, energy consumption and techno-economic analysis are discussed, aiming at optimizing microwave pyrolysis process from multiple perspectives. The key problems and solutions of microwave pyrolysis to generate biogas are investigated and proposed to understand the critical issues that hinder its further development. This review provides new thinking and references for the application and industrialization of microwave pyrolysis technology in producing high-quality biofuels.

Agricultural biogas plants as a hub to foster circular economy and bioenergy: An assessment using substance and energy flow analysis

Abstract: Today's agro-food system is typically based on linear fluxes (e.g., mineral fertilizers importation) when a circular approach should be privileged. The production of biogas as a renewable energy source and digestate as an organic fertilizer is essential for the circular economy in agriculture. This study investigates the current utilization of biomass in agricultural anaerobic digestion plants in Switzerland in terms of mass, nutrients, and energy flows to assess its contribution to the circular economy and climate change mitigation through the substitution of mineral fertilizers and fossil fuels. We quantify the system and its benefits in detail and examine potential future developments using different scenarios. Today, agricultural anaerobic digestion provides 1300 TJ/a of biogas. Our results demonstrate that the system could be largely expanded and provide ten times more biogas by 2050 while saving significant mineral fertilizer amounts (over 10 kt/a of dry mass nutrients yielding 38 kt/a of CO2 equivalent).

Perspectives for the Use of Biogas and Biomethane in the Context of the Green Energy Transformation on the Example of an EU Country

Abstract: Natural gas is the primary source of energy, accounting for around 20% of the world’s energy production. It is also a key element in reducing CO2 emissions due to its key role in stabilizing renewable energy sources. At the same time, natural gas as a fossil fuel that emits CO2 should be limited. A natural candidate that can ensure the stabilization of RES and at the same time reduce the demand for fossil fuels is biogas. Successful use of biogas requires a thorough understanding of the potential, structure, and specifics of its sources and production technology. The presented study provides a perspective and a brief overview of the existing potential of biogas production. Poland was chosen as the case study and it was shown that almost 90% of the Polish biogas potential comes from sources with a capacity below 100 Nm3/h, which is the current minimum commercially available capacity of the biogas purification and liquefaction technologies. Consequently, full utilization of these sources would require a downsizing of these technologies.

Anaerobic digestion of organic waste allows recovering energy and enhancing the subsequent bioplastic degradation in soil

Abstract: The bioplastics within organic municipal waste are a critical component for the future of waste management with particular reference to the quality of the final products, i.e., digestate and compost. Moreover, to promote a circular economy they need to be recovered to produce new material and/or energy. This study compared polylactic acid (PLA) and starch based (SB) materials which were subjected to anaerobic digestion (AD) treatments producing biomethane, and the fate of residual bioplastics when incubated in soil were then evaluated. Results indicated that AD processes affected both PLA and SB characteristics, influencing their subsequent degradation in soil. Comparative material balance, considering the whole process, indicated that SB bioplastics degraded by 50%, while PLA achieved overall degradation by 70% when thermophilic AD was applied. The insights obtained contribute to understanding the fate of bioplastics and confirmed the role of AD as method for waste valorization in a circular economy perspective.

Optimization of Operating Parameters for Two-Phase Anaerobic Digestion Treating Slaughterhouse Wastewater for Biogas Production: Focus on Hydrolytic–Acidogenic Phase

Abstract: In a two-phase anaerobic digestion process, enhanced biogas production and organic pollutant removal depend on the stability and performance of the hydrolytic–acidogenic and methanogenic phases. Additionally, the hydrolytic–acidogenic phase is a rate-limiting step, which calls for the further optimization of operating parameters. The objective of this study was to optimize the operating parameters of the hydrolytic–acidogenic reactor (HR) in the two-phase anaerobic digestion treating slaughterhouse wastewater. The experiment was carried using bench-scale sequential bioreactors. The hydrolytic–acidogenic reactor operating parameters were optimized for six different hydraulic retention times (HRTs) (6–1 day) and organic loading rates (OLRs) (894.41 ± 32.56–5366.43 ± 83.80 mg COD/L*day). The degree of hydrolysis and acidification were mainly influenced by lower HRT (higher OLR), and the highest values of hydrolysis and acidification were 63.92% and 53.26% at an HRT of 3 days, respectively. The findings indicated that, at steady state, the concentrations of soluble chemical oxygen demand (SCOD) and total volatile fatty acids (TVFAs) decrease as HRT decreases and OLR increases from HRTs of 3 to 1 day and 894.41–1788.81 mg COD/L*day, respectively, and increase as the HRT decreases from 6 to 4 days. The concentration of NH4+-N ranges from 278.67 to 369.46 mg/L, which is not in the range that disturbs the performance and stability of the hydrolytic acidogenic reactor. It was concluded that an HRT of 3 days and an ORL of 1788.81 mg COD/L*day were selected as optimal operating conditions for the high performance and stability of the two-phase anaerobic digestion of slaughterhouse wastewater in the hydrolytic–acidogenic reactor at a mesophilic temperature. The findings of this study can be applicable for other agro-process industry wastewater types with similar characteristics and biowaste for value addition and sustainable biowaste management and safe discharge.