The development and validation of a comprehensive dynamic simulation model of the anaerobic fermentation of animal waste have been described by Hill. This model has proved to be highly accurate, both qualitatively and quantitatively, in predicting the steady-state methane productivity of conventional fermentation plants and in simulating the transient-state response of semi-batch fed digesters. Simulation studies using this model have been performed and results have been used to develop design recommendations for steady-state operations. These simulation studies have also produced a start-up procedure that will ensure successful initial operation of the digestion system and, more importantly, have allowed determination of the operational techniques that will provide recovery from failure due to organic overloading or excessively short detention time. This paper describes the results of these studies for swine and poultry (caged layer) waste and presents the design recommendations and operating techniques developed from the simulations. (Refs. 11).