Synergistic Enhancement of Biogas Production: Combined Effects of Feed Dilution, Additives, and Sonication Pretreatment

Biogas represents a viable renewable energy source that is a clean alternative to fossil fuels. It is especially feasible for rural communities. It is a source of energy that is easily accessible, especially in an agriculture-heavy country like India, especially in rural areas. However, its use has been constrained due to low methane yields, and inefficient substrate utilization. In this study, the biogas yield was enhanced through integrated strategies involving the use of locally available agricultural additives, fish waste, and ultrasonication. The synergistic impact of feed dilution, organic/inorganic additives, and sonication pretreatment on biogas production was studied and has not previously been explored much. Batch experiments were conducted over 60 days using cow dung as the base substrate. The substrate was diluted at ratios of 1:1 and 1:3 and supplemented with organic additives (cabbage, fish waste, and flax seeds) and an inorganic additive (sodium bicarbonate). Additionally, sonication pretreatment was applied to selected reactors to improve substrate disintegration. The 1:1 reactor was taken as the control reactor, to which all other reactors were compared. Overall, among the organic additives, cabbage yielded the greatest improvement at 23.3%, whereas sodium bicarbonate increased biogas production by 23.1% possibly through pH stabilization. Furthermore, sonication pretreatment with flax seeds gave the best results with significantly increased substrate digestibility, resulting in a remarkable 78.8% increase in biogas yield. This study reports the combined effects of various factors such as dilution, additives, and sonication, demonstrating a substantial improvement in both biogas yield and methane enrichment.