ABSTRACT
Anaerobic digestion of waste materials has been a long standing method of treatment in municipal sewage plants. American dairymen and cattlemen, along with the American farmer, have become very concerned about both the cost of energy and the availability of fuel in this time of inflation and political unrest. The plug-flow digester has been demonstrated to be very efficient in the production of fuel gas and coproducts. This chapter discusses its operation and energy balance, as well as the properties of its solid effluent as a feed component. In terms of on-farm anaerobic digestion, there are more plug-flow digesters operating with long-term success than either of the other types. Energy Cycle, Inc., a subsidiary of Butler Manufacturing Co., and its predecessor company have built six plug-flow, mesophilic digesters at five large dairy farms in the US since 1979. A number of investigators have studied digester solids as a cattle feed component and concluded that it has good potential and value.
