5 – Fundamental science and engineering of the anaerobic digestion process for biogas production

: The aim of this chapter is to explain, in a simplified manner, the complex microbiological process of anaerobic digestion and detail the relationship between feedstock, anaerobic digester and methane production. The chapter first reviews basic microbiology and explores the interplay between the different groups of bacteria, the conditions under which they prosper and potential sources of inhibition. Then, the chapter deals with engineering aspects – categorisation of feedstocks, methane production per unit of feedstock, reactor configurations, mass and energy balance of digestion systems, up-scaling laboratory systems to commercial reality and modelling. In the analysis, an emphasis is placed on high solid content feedstocks. Two different feedstocks are highlighted – the organic fraction of municipal solid waste and grass silage.

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