Environmental Engineering Reference
In-Depth Information
Production of Methane Biogas as Fuel Through
Anaerobic Digestion
Zhongtang Yu and Floyd L. Schanbacher
Abstract
Anaerobic digestion (AD) is a biotechnology by which biomass is con-
verted by microbes to methane (CH
4
) 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., polysac-
charides, proteins, and lipids) present in the feedstock and further ferment the
resulting hydrolysis products to short chain fatty acids (SCFA), H
2
and CO
2
, which
are ultimately converted to methane biogas (a mixture of CH
4
and CO
2
) 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 imple-
mentation 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.
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