Biomethane from Dairy Waste

A Sourcebook for the Production and Use of Renewable Natural Gas in California

Executive summary

This report examines the feasibility of producing biomethane from dairy manure. The authors investigated a number of possible technologies for producing renewable forms of energy and fuel from dairy wastes as well as applications and markets for these products. Although some of the applications proved to be technically or economically infeasible at this time, they believed that the information gathered could prove useful for other investigators or future studies. With this in mind, they designed this sourcebook for readers and investigators interested in exploring alternate uses of biogas created from dairy wastes.

Structure of Report

The report deals with five major areas of investigation:

• Producing biogas from California dairy wastes. We considered the theoretical maximum production potential, the technical and economic considerations, and the technologies and systems most suitable for producing biogas on dairy farms.
• Upgrading biogas to biomethane. We use the term “biomethane” to describe an upgraded form of biogas similar to natural gas in composition and energy capacity, and we investigated the various technologies that can be used to create biomethane by removing hydrogen sulfide, moisture, and carbon dioxide from biogas.
• Using and distributing biogas and biomethane. We investigated various traditional and non-traditional uses of biogas and considered potential on- and off-farm uses of biomethane. An important consideration is the means of storing and transporting the fuel to its final place of consumption. We considered the technical and economic implications of the various means of distribution.
• Meeting regulatory requirements and obtaining access to government incentives. Most existing government policies and incentives for renewable energy focus either on renewable electricity sources or two forms of alternative vehicle fuels: ethanol and biodiesel. We examined federal and state (California) policies and programs now in place to determine their current or potential applicability to the dairy biogas and biomethane industry. We also considered the various permits and regulatory requirements needed to build a dairy digester and/or biomethane upgrading plant, whether on an individual farm or at a centralized location.
• Determining the financial, economic, and business environment for the development of a biomethane industry. We estimated the costs of building a biomethane plant and considered these in the context of existing and potential markets for biomethane. Despite some favorable economic conditions, such as the currently high price of natural gas, we concluded that public (i.e., governmental) policy support of the industry is needed to help move it beyond the pioneering stage, and we concluded that the various environmental, social, and economic benefits associated with the development of such an industry justify this support. We also determined a logical process for analyzing and developing specific biomethane projects and provided some scenarios for five projects that we believe have the best chance for success.

See also the Storage and transportation of biogas and biomethane summary report