In addition to the sun, many other renewable power sources exist, and a number of them may be particularly well-suited to rural sites. Small-scale wind power, biomass generation, micro-hydro power, and methane digesters are all potential sources of renewable power for agricultural buildings.
Anaerobic Digestion of Animal Wastes: Factors to Consider
Rising energy prices, broader regulatory requirements, and increased competition in the marketplace are causing many in American agriculture’s livestock sector to consider anaerobic digestion of animal wastes. They view the technology as a way to cut costs, address environmental concerns, and sometimes generate new revenues.
While hundreds of anaerobic-digestion projects have been installed in Europe and the U.S. since the 1970s, it was not until the 1990s that better designed, more successful projects started to come on line in the U.S. Today, there are an estimated 40 farm-scale projects in operation on swine, dairy, and poultry farms across the country. The key by-products of anaerobic digestion include digested solids (useful as a soil amendment) and methane, the primary component of “bio-gas,” which can be used to fuel a variety of cooking, heating, cooling, and lighting applications, as well as to generate electricity.
Capturing and using the methane also precludes its release to the atmosphere, where it is 20 times more damaging to the ozone layer than carbon dioxide. Despite the many benefits, anaerobic-digestion systems are not appropriate for all farm operations. AgStar, a cooperative effort by the U.S. Departments of Agriculture and Energy and the Environmental Protection Agency to promote bio-gas projects, estimates that anaerobic digestion could be cost-effective on about 3,000 U.S. farms. The critical issue is planning, with each system needing to be designed to accommodate a variety of factors.
Risks Associated with Bio-gas
While methane is a very promising energy resource, the non-methane components of bio-gas tend to inhibit methane production and, with the exception of the water vapor, are harmful to humans and/or the environment. For these reasons, the bio-gas produced should be properly “cleaned” using appropriate scrubbing and separation techniques. In addition, the methane itself represents a serious danger, as it is odorless, colorless, and difficult to detect.
Methane is also highly explosive if allowed to come into contact with atmospheric air at proportions of 6-15 percent methane. For these reasons, it is recommended that buildings be well ventilated; motors, wiring, and lights should be explosion-proof; flame arrestors should be used on gas lines; and alarms and gas-detection devices should be used.