Potentials and obstacles for community anaerobic digesters in the United States: Evidence from a case study in Vermont

Abstract

The two purposes of this study are to identify factors for the failure of 31% of community anaerobic digesters (CADs) in the United States through a case study of the development, operation, and shutdown of a $4.5 million CAD in Vermont, and to derive policy recommendations for sustainable development of CADs. While many studies have used aggregated data to assess the potentials, obstacles, and policy implications of on-farm biogas production, this paper contributes to the literature with a case study of a large CAD's investment and funding sources, feedstock utilization, energy output, and operating costs and revenues over multiple years. Empirical findings suggest that it is technically feasible to use cow manure and organic wastes from multiple sources to generate electricity, but the economic feasibility and returns depend highly on grants and subsidies for initial investments and on such factors as electricity price, feedstock availability and quality, and market price of renewable energy credits (RECs). Major reasons for the shutdown of this CAD, and likely a large proportion of other CADs in the country, include underestimation of technical problems and operating costs, overestimation of financial returns, and low REC price in the past several years. Future CADs should be invested in and operated by commercial enterprises and government subsidies, and public supports should be based on CADs' outputs such as electricity and utilization of their byproducts like waste heat and recycled nutrients. Also, the educational and research needs of nonprofit organizations could be met via collaboration with privately operated CADs.