In late May, Hewlett-Packard engineers presented a research paper at the American Society of Mechanical Engineer’s conference, showing that “digested farm waste” could be used to generate electricity. According to the HP study, 10,000 cows can produce up to 1MW of power, way more than what is required by the typical TV station.
The actual conversion process is not new, as some farms already use organic waste and a process called anaerobic digestion to produce methane-rich biogas. The methane is then burned to power a steam generator, which produces electricity.
This solution might require TV stations to relocate near a large dairy farm. Then there is the problem of getting 10,000 cows to cooperate.
According to environmental consultant Angie McEliece, the reality of grouping 10,000 cows in once place is actually small. “The average size dairy farm in the U.S. includes less than 1000 cows; farms with 5000 cows is quite unusual”, she said.
Also, the solution requires the right kind of cows. A feedlot steer produces 4.45 metric tons of manure per year. A dairy cow produces lots more manure, 20 metric tons per year. From an efficiency standpoint, the TV station therefore should be located near a dairy farm, not a feedlot.
The HP research shows that the manure from one dairy cow can produce 3.0kWh of energy per day. With that factor, it becomes simple to determine how many a TV station would need to power its operation.
McEliece says that farms already use an anaerobic digestion system to generate electricity and heat. The systems needed to build such power plants often receive federal and state grants. In such cases, ROI can be as little as four years. Even without grants, the payback can be about 10 years, according to McEliece.
The U.S. Environmental Protection Agency estimates that there are 125 operating digester projects at commercial livestock facilities in the United States. In 2008, those facilities produced a total of 290 million kWh of electricity.
An example of a power generation station block diagram is shown to the right. This chart, provided by HP Labs, illustrates the conversion of cow manure to electricity.
One element not addressed in the HP research was odor. Perhaps the station’s personnel will just have to get used to smelling the benefits of green power.