by Bruce Dorminey, via Renewable Energy World
For years, third world ranchers have been using methane from manure to run electrical generators down on the farm. This clean-burning biogas is not only a good local fuel in countries with little or no infrastructure, now even countries like the U.S. are reaping energy from this foul-smelling source.
Some 80 percent of the estimated 160 biogas energy projects in the U.S. are currently installed on dairy farms, which then combust the gas to generate electricity. The combined installed capacity of all dairy farm projects is nearly 60 MW.
It’s a complicated process. First the farms have to facilitate both the production and collection of biogas in anaerobic digesters. These are processing systems that allow methanogenic bacteria to feed on the manure’s natural acids in a very oxygen-depleted environment. In turn, the bacteria both generate methane-rich biogas and reduce the manure’s foul odor by as much as 90 percent.
After collection from storage systems such as covered lagoons — akin to large swimming pools very nearly brimming with manure — this gas is usually piped to an electrical power generator.
Although a large portion of the U.S.’ biogas energy projects are found in New York, Pennsylvania, Vermont, and Wisconsin, they represent only a fraction of the estimated 8,000 farms out there that could support some method of biogas energy production. By some estimates, the total electrical capacity of all these farms could range as high as 1,600 MW. That’s about 10 percent of the U.S.’ current electricity needs.
To date, Vermont has been a standout. Since 2002, Central Vermont Public Service, the state’s largest utility, has delivered over 47 million kWh of local “Cow Power” to some 3 percent of its 160,000 customers.
Dave Dunn, an animal scientist with the Vermont utility, says that while its cow power customers are mostly homeowners, they also have 200 non-residential customers, from a gas station to a brewery to Green Mountain College in Poultney. The college now gets about half of its monthly electricity (100,000 kWh) from the utility’s biogas energy program.