Agricultural wastes co-densification: A solution for seasonal feedstock storage and anaerobic digestion performance improvement

Unravelling barriers associated with dissemination of large-scale biogas plant with analytical hierarchical process and fuzzy analytical hierarchical process approach: Case study of India

This study explores why large-scale biogas plants are not widely installed in India despite the wealth of biomass resources. The methodology includes an extensive literature review and surveyed biogas experts in different sectors, such as private, public, and academic, to identify and rank key obstacles using the Analytical Hierarchy Process (AHP) and Fuzzy-AHP techniques. Overall, 27 barrier elements were identified across six different categories. As perceived by different experts, except for financial barriers, notable differences were found in the relative importance of other barrier categories. Among the different barriers, competition from other fuels, subsidies, lack of financing mechanisms, and feedstock variation are the most influential. To overcome these challenges and successfully promote the growth of the biogas sector in India, a combination of financial strategies, collaborative efforts, standardized procedures, and comprehensive resource mapping were proposed. These measures can inform effective policy development and contribute to achieving numerous Sustainable Development Goals.

Co-densification of rice straw and cow dung in different food-to-microorganism ratios for biogas production

Agricultural residues such as rice straw (RS) are desirable raw materials for biogas generation. However, the recalcitrant nature of RS hinders biogas production, and its low bulk density increases storage space requirements, transportation needs, and overall costs. These challenges could be resolved by pretreatment and pelletization. In this study, various thermal pretreatments were performed, and the best conditions (temperature and time) were identified. Also, rice straw and cow dung pellets (RCP) at different food-to-microorganism (F/M) ratios (0.5-2.5) were prepared. Parameters such as bulk density, moisture absorption, and drop shatter tests were conducted to evaluate the physical properties. Finally, the biochemical methane potential (BMP) study of the best RCP with varying total solids (TS: 4-12%) content was investigated. The results indicate that hot air oven pretreatment (for 60 min at 120 °C) resulted in maximum solubilization. In physical characteristics, RCP with an F/M ratio of 2.5 pellets was ideal. The bulk density of RCP 2.5 was found to be around 25 times that of the raw. Also, the TS 8% yielded maximum biomethane (279 mL/g-VSconsumed) as compared to other TS contents. Overall, this study will propel the growth of bioenergy while simultaneously tackling the pressing issues related to RS management.