Biomethane Recovery From Industrial Organic Waste: Effect Of Substrate Type And Food-To-Microorganism (F/M) Ratio

Food processing and packaging industries witnessed significant increase during recent decades to keep pace with population growth. Municipalities around the world are therefore adopting circular economy approach to resolve growing industrial waste generation and achieve zero-emission by 2050. Several studies indicated that anaerobic digestion (AD) process is a promising technique for waste treatment due to its low carbon footprint and potential for recovering several value-added products including biomethane. In this study, AD processing was investigated using five industrial wastes including bakery processing and kitchen waste (BP+KW) mixture, fat, oil, and grease (FOG), powder whey, ultrafiltered (UF) milk permeates, and pulp and paper (P&P) compost. Biochemical methane potential (BMP) was conducted under mesophilic conditions for 40 days to investigate biomethane generation at different food-to-microorganism (F/M) ratios of 1, 2, 4, and 6. Experimental results showed that methane yield values decreased with increasing F/M ratios for all feedstocks. The most optimum ratio for methane yield in all feedstocks was F/M=1 g TCOD/g VSS except for powder whey at which F/M=2 was the optimum ratio. The maximum methane yield values were 454 mL CH4/ g VS added (336 mL CH4/ gTCOD added) for FOG and the lowest value of 190 mL CH4/ g VS added (135 mL CH4/ gTCOD added) for P&P at F/M=1. Pearson’s coefficient values ranged from -0.85 to -0.97 for all feedstocks: thus, indicating a strong inverse correlation between methane yield and increasing F/M ratios. Process kinetics was also investigated using first-order model where the highest reaction rate coefficient (k) values were observed for FOG