Environmental Engineering Reference
In-Depth Information
6
Optimisation of biogas yields from anaerobic
digestion by feedstock type
CHARLES J. BANKS andSONIAHEAVEN,
University of Southampton, UK
DOI: 10.1533/9780857097415.1.131
Abstract: This chapter considers optimisation of a biogas plant from a
number of different perspectives. These include creating ideal conditions
for microbes, maximising the overall net energy yield, and achieving the
full range of environmental benefits of anaerobic digestion (AD). Basic
concepts of digester loading and hydraulic retention time are explored
and the relationship between them demonstrated for different feedstock
types. The limitations on the performance of a digester are explained in
terms of metabolic capacity and examples are given of how these can be
minimised in practice. The importance of digester operating conditions is
examined, including the role of temperature, macronutrients and
micronutrients, and mixing and mass transfer. The need for pre-
treatment and the advantages of co-digestion of feedstocks to balance
nutrient requirements are discussed. Selection of digester type is also
considered in relation to the feedstock. The chapter concludes with three
case studies to illustrate optimisation of the AD process to meet different
goals.
Key words: optimisation, feedstock selection, pre-treatment, metabolic
capacity, specific methane yield, volumetric productivity.
6.1
Introduction
This chapter considers optimisation of biogas yield from the anaerobic
digestion (AD) process by looking at some of the factors that may influence
the performance of the plant with respect to its functionality as a waste
treatment process, as a source of renewable energy and to the role it may
have in environmental protection. These factors are considered in relation to
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