Water Intelligence Online ©IWA Publishing 2002

Fundamentals of the Anaerobic Digestion Process

J. Mata-Alvarez
[University of Barcelona, Marti i Franques No 1 pta.6, 8028 Barcelona, Spain]

Anaerobic digestion is a process which, in the absence of oxygen, decomposes organic matter. The main product is biogas a mixture of approximately 65% methane and 35% carbon dioxide along with a reduced amount of a bacterial biomass. The development of anaerobic digestion technology took place at the beginning of the 19th century, although after the Second World War biological aerobic treatments and tertiary treatments were the main features of the incipient waste-treatment processes. However, owing to the energy crises of the 1970s, anaerobic digestion technology underwent significant growth.Traditionally, anaerobic digestion (AD) has been used to treat liquid wastes with or without suspended solids, such as manures, domestic or industrial wastewaters, sludges from biological or physico-chemical treatments, etc.

In Europe the beginning of the study of anaerobic digestion of solid waste took place later, in the 1980s, and was dedicated directly to the organic fraction of municipal solid waste (OFMSW). Anaerobic digestion of solid wastes includes many aspects. OFMSW is a specific waste, characterized by its complexity. In this book, many of these aspects are examined: from the more theoretical to the more practical.

In this chapter, and next one, the fundamental issues are reviewed. Some description of the metabolic pathways is presented, with special attention to the thermodynamics, so as to see the importance of some intermediates of the process. Environmental factors such as the presence of nutrients and the presence of inhibitors or toxicants, together with the effect of temperature, are also considered. This is important to understand the phenomena going on inside the reactor and to help in interpreting the values of the measured variables. Finally some description of the control strategy for anaerobic digesters is also given.

Full article (PDF Format)

UNIQUE ID: 200208001

[Taken from the book 'Biomethanization of the Organic Fraction of Municipal Solid Wastes' ©2002 IWA Publishing ISBN: 1900222140]