Farm-based anaerobic digesters as an energy and odor control technology: Background and policy issues

This chapter summarizes the existing literature and analytical perspectives on farm-based digesters, highlights major efforts in the United States and Europe to expand digester usage, and discusses key policy issues affecting digester economics. The study was largely a review of the "gray literature" on digesters, and it serves as a snapshot overview of the industry. Digesters are fairly capital-intensive when viewed primarily as an energy source. On a strictly market basis, current U.S. average electricity prices do not appear to provide sufficient economic justification for digesters to move beyond a fairly limited niche. Digesters make the most sense today where the odor and nutrient management benefits are important, or where the electricity or heat has a higher-than-average value. Digester biogas is mainly methane, which is destroyed when flared or used for electricity. This methane destruction is beneficial in terms of climate change. The associated carbon credits may become a more significant farm revenue source in the future.