Evaluation of animal- and plant-based lipidic waste in anaerobic digestion: kinetics of long-chain fatty acids degradation

Recently, lipidic wastes have been reported to enhance biomethane production through anaerobic co-digestion (ACD). These lipidic wastes were of animal and plant origins. The comparison of animal and plant lipidic wastes with the microbial communities involved in lipid degradation have not been given adequate attention in pervious reviews. However, there is need to demonstrate the differences between these wastes in terms of their long-chain fatty acids (LCFAs) composition, nature, and availability. This review discusses the characterization and comparison of animal and plant lipidic wastes as co-substrates, while summarizing the potential of biomethane production in the laboratory, as well as pilot and full-scale operations. The degradation kinetics of LCFAs existing in animal and plant lipidic wastes were also highlighted during the operation process, along with the challenges (such as inhibition by LCFAs, sludge washout, sludge flotation, and foaming). Discussion on the use of the next gene sequencing (NGS) for the microbial community in the ACD of lipidic wastes was considered to understand the interspecies interactions among various microbes. The economic feasibility of lipidic wastes in the ACD along with biogas yield has also been evaluated. The use of lipids (animal and plant based) in anaerobic digestion with the application of combined pretreatment or an acclimatized microbial consortium could be a potential approach for maximum energy recovery from the waste in terms of biomethane production.