Anaerobic Digestion Systems

ing the installation of anaerobic digestion systems and the equipment necessary to generate electricity from the methane produced and collected by these systems. There are several reasons these systems are being considered: decreasing onfarm energy costs by using methane to generate electricity; mitigating odor problems on livestock operations; and improving the handling of manure nutrients and control pathogens. In addition, electrical generator companies are mandated in some areas to increase the amount of “green” energy produced, and may pay a premium for it. However, producing and managing methane requires a substantial commitment of financial and management resources on the part of the operator. Farmers need thorough and accurate information before starting methane production on their farm. Anaerobic digestion and the production of methane gas are not new concepts. They have been used profitably for many years in the waste management industry (municipal wastewater treatment plants and sometimes landfills). Until recently however, not many farms were generating electricity. Recent changes in the rising cost of energy, improvements in the technology used to convert methane to electricity and the environmental pressures agriculture is facing in terms of livestock production, has increased interest in anaerobic digestion systems. The purpose of this publication is to provide brief answers to the common questions farmers often ask about anaerobic digestion and methane generation. It is not our goal to provide all the information needed to make a decision on whether or not this technology will work on your operation. The goal of this publication is to provide information on the basic questions producers have. Once you have answered these questions and you desire additional information, more detailed and specific guidance can be found in the recommended publications, web sites and other materials referenced by this publication. In general, a well-designed and managed anaerobic digester will have few safety concerns. Still, the gas-handling components of the digester and engine-generator must be designed to ensure safety. Inhalation of biogas can pose health risks, and biogas is flammable and even explosive in confined spaces. There are only a few examples of methane digesters on which to base construction costs. Numbers vary, but some examples indicate about $250,000 for a 1,000-cow dairy operation. In many cases, farmers have found low-cost loans or even grants to assist in start-up. This $250,000 estimate includes design, engineering, construction, generator and engine, and some electrical connections, depending on how sophisticated they need to be.