Simulation and Optimization of an Anaerobic Digestion System

An automated procedure for the design of an optimized (for both configuration and operating point) anaerobic digestion system is presented. The procedure is based on modern nonlinear programming algorithms and numerical models of the various system components (biological, thermal, and economic). The model simulates yearly digester system operation, and uses this to calculate the after-tax net present value for a particular system design. The optimal design is found using BIAS, a method of multipliers code. Substantial improvements in the net present value were found when the optimized design was compared to the designs in current use. A sensitivity analysis revealed that the price of energy and the energy conversion efficiency were the parameters which influenced system economics most strongly for the best system configuration at the optimal operating point.