An Analysis of Anaerobic Digestion System Costs on U.S. Livestock Production Systems

Abstract

Most manure anaerobic digestion systems built to date in the United States have included electrical generation capacity with the intent of enabling the producer to directly sell electricity to a utility company. An analysis of 38 existing US manure anaerobic digestion systems indicates that the omission of electrical generation equipment would lower the initial digester capital cost by approximately 36%. Given the increase in natural gas prices over the past five years, the direct use of biogas as a replacement for natural gas or propane for on-site heating purposes (e.g. heating water, heating animal housing, etc.) would provide economic benefits to animal producers with a consistent year-round requirement for the biogas. When generator sets are removed from the digester system design, costs as well as maintenance measures are reduced. The cost analysis conducted suggest that the lower cost anaerobic digestion systems currently employed on US farms can provide biogas that is competitive or lower in cost than the current $0.12/m3 ($11.60/1000 ft3) US natural gas price if the biogas can be used directly in space heaters or boilers without excessive gas cleaning costs. Based on the analysis completed in this study, the direct use on the farm for biogas produced via a manure anaerobic digestion system appears to be economically feasible when the on-farm heating requirements are high enough to utilize the biogas produced by the system.