There is now an increasing concern in many countries about pollution of land, water and the atmosphere by effluents from factories, farms and domestic sources, and the number of papers on digester feedstocks and effluents, on the design and running of digesters of all forms, and on the biochemistry, microbiology and theoretical aspects of digestion has increased exponentially. It seemed that it was time to review the developments in the theory and practice of digestion during the 1980s to give readers the basic facts about the process and to guide them to relevant papers from which they could proceed futher if needed. This book should be of interest to the microbiology and biochemistry student and lecturer in describing the application of microorganisms to what is still the largest biotechnology industry - waste treatment. The scientist working on one aspect of digestion should find information on other applications of the process and while engineering aspects are not dealt with in detail, the engineer should find information of use in design and running of parts.