The effects of phytochemicals on methanogenesis: insights from ruminant digestion and implications for industrial biogas digesters management

The overarching objective of this review is to compare methanogenesis in ruminant gut systems and industrial digesters that employ plants, crops and their processing residues or by-products as feedstocks. An important consideration is the presence of phytochemicals in these feedstocks, with the understanding that depending on the type and quantities, these phytochemicals affect the activity of biomass degrading microorganisms to varying extents. This review aims to evaluate currently available knowledge on the effects of phytochemicals in ruminants' methanogenesis as well as industrial anaerobic digestion processes. Technology and scale up in industrial fermentation have always benefited from our understanding of natural biological processes as such, knowledge from the process of methanogenesis in the gastrointestinal tract of ruminants can be used to make inferences about the performance of industrial digester systems for biogas production. This is particularly important when the same feedstock is used in both systems. Thus, in this review, comparisons of the two methane generating systems are discussed with an emphasis on phytochemical inhibitory effects on microorganisms that are involved in anaerobic digestion.