Impacts of low biodegradable wastewater on biogas production from food wastes: a comprehensive review of challenges and enhancement strategies

Low biodegradability wastewater greatly restricts biogas production in co-digestion with food wastes in anaerobic digestion operations. This review critically addresses the impact of low biodegradability wastewater on biogas yield, process kinetics, and stability. Low biodegradability wastewaters consist of recalcitrant complex organics that inhibit microbial degradation, leading to reduced methane yield and increased lag times. Additionally, inhibitory substances such as volatile fatty acids and ammonia buildup lead to process destabilization. The review summarizes current research on the detrimental effects and discusses augmentation methods such as mechanical, chemical, and biological pretreatment processes that enhance substrates’ biodegradability. Besides, co-digestion methods of low and high biodegradability substrates are presented as viable options to nutrient balancing, inhibitor reduction, and microbial activity promotion. Process optimization and microorganism enrichment also enhance enhanced methane production and system stability. This comprehensive review demonstrates both the issue brought about by low biodegradability wastewater and effective solutions to rectify them, presenting practical information to maximize biogas production from mixed waste streams for sustainable waste-to-energy conversion.