Economic sustainability of a biomass energy project located at a dairy in California, USA

Previous experience has demonstrated the tenuous nature of biomass energy projects located at livestock facilities in the U.S. In response, the economic sustainability of a 710 kW combined heat and power biomass energy system located on a dairy farm in California was evaluated. This biomass energy facility is unique in that a complete-mix anaerobic digester was used for treatment of manure collected in a flush-water system, co-digestates were used as additional digester feedstocks (whey, waste feed, and plant biomass), and the power plant is operating under strict regulatory requirements for stack gas emissions. Electricity was produced and sold wholesale, and cost savings resulted from the use of waste heat to offset propane demand. The impact of various operational factors was considered in the economic analysis, indicating that the system is economically viable as constructed but could benefit from introduction of additional substrates to increase methane and electricity production, additional utilization of waste heat, sale of digested solids, and possibly pursuing greenhouse gas credits. Use of technology for nitrogen oxide (NOx) removal had a minimal effect on economic sustainability.