Production of methane biogas as fuel through anaerobic digestion

Abstract

Anaerobic digestion (AD) is a biotechnology by which biomass is converted by microbes to methane (CH4) biogas, which can then be utilized as a renewable fuel to generate heat and electricity. A genetically and metabolically diverse community of microbes (mainly bacteria and methanogens) drives the AD process through a series of complex microbiological processes in the absence of oxygen. During AD, bacteria hydrolyze the polymeric components (e.g., polysaccharides, proteins, and lipids) present in the feedstock and further ferment the resulting hydrolysis products to short chain fatty acids (SCFA), H2 and CO2, which are ultimately converted to methane biogas (a mixture of CH4 and CO2) by archaeal methanogens. Various biomass wastes (e.g., livestock manure, crop residues, food wastes, food-processing wastes, municipal sludge, and municipal solid wastes) are especially suitable for AD. As one of the few technologies that can both cost-effectively generate bioenergy and reduce environmental pollution, AD has been increasingly implemented in different sectors to convert otherwise wasted biomass to bioenergy. AD technologies can be categorized in many different ways. Each AD technology has its own advantages and disadvantages that make it suitable for particular feedstocks or objectives (i.e., production of energy or stabilization and treatment of wastewaters). Both drivers and barriers exist for commercial implementation of AD projects, with the former stimulating, enabling, or facilitating AD implementation, while the latter function in opposite direction. This chapter will provide an overview of the microbiology underpinning the AD process, and discuss the characteristics of the biomass wastes suitable for AD and the AD technologies appropriate for each type of these feedstocks. The drivers and barriers for AD as well as the AD technology gaps and future research needs will also be discussed. © 2010 Springer Science+Business Media B.V.