Thursday, April 10, 2008

In California and North Carolina, new projects tap cow and pig manure to generate energy

The annual Wisconsin State Cow Chip Throw and Festival in Prairie Du Sac, and many other such events, have fun with dried manure. The wet version is no fun, except perhaps to laugh at someone who steps in it, but it does have potential when it comes to energy.

Riverdale, Calif., dairyman David Albers sees the potential in cow patties, and his Vintage Dairy Biogas Project is turning manure into natural gas for Pacific Gas & Electric "in what the utility hopes will be a new way to power homes with renewable, if not entirely clean, energy," reports Nichola Groom of Reuters.

The project has a goal of delivering enough natural gas to power 1,200 homes a day by harnessing the methane produced by decomposing cow manure. Methane is a greenhouse gas, and scientists have said controlling it — specifically as it created by animal wastes — might help curb global warming. Groom explains the process that transforms the waste into energy:
To tap the renewable gas from cow manure, the Vintage Dairy farm first flushes manure into a large, octagonal pit where it becomes about 99 percent water. It is then pumped into a covered lagoon, first passing through a screen that filters out large solids that eventually become the cows' bedding.

The covered lagoon, or "digester," is the size of nearly five football fields and about 33 feet deep. It is lined with plastic to protect the groundwater, and the cover, made of high density polyethylene, is held down at the edges by concrete. The digester's cover was sunken into the lagoon recently, and officials said it would be taut and raised in a few days as the gas collects underneath it.

Weights on top of the digester channel the gas to the small facility where it is "scrubbed" of hydrogen sulfide and carbon dioxide. The end product is "close to 99 percent pure methane," according to BioEnergy Chief Operating Officer Thomas Hintz.
California has 2 million dairy cows, and there are other similar projects in the works. A key factor is a farm's proximity to gas transmission lines, essential to its participation. (Read more)

In North Carolina, the Swine Farm Methane Capture Pilot Program is seeking 50 farms to sell electricity made from hog wastes, reports Ann Bagel Storck of "Selected farms will capture methane gas generated by their waste systems either by full or partial lagoon covers and use the gas to generate electricity," she writes. "The methane conversion systems must be operational with electricity available for purchase by Sept. 1, 2010." (Read more; subscription required)

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