Click on “Download PDF” for the PDF version or on the title for the HTML version.

If you are not an ASABE member or if your employer has not arranged for access to the full-text, Click here for options.

A full-scale biomass energy system located at a dairy farm in Central California was rigorously studied for 15-months following construction in 2009 to determine the sustainability of continued operations. During that time period the anaerobic digesters produced 6,300 m3/d of biogas containing 49.7% methane, resulting in greenhouse gas reduction equivalent to 6,900 metric tons of carbon dioxide annually. Of the biogas produced 97.1% was used in a combined heat and power unit, which resulted in power production of 9,700 kWh/d. Revenues and cost savings from the project appeared sufficient to offset system costs (reduced by state and federal grants) over the 20 year projected lifespan of the project when a 4% discount rate was applied. The estimated net present value of the project was $1.1 million and the estimated payback period was 12.1 years. Sustainability of continued operations could be improved by operating the system closer to capacity, importing off-site digester feedstocks, obtaining carbon credits, and pursing additional use of waste heat.