Instead of collecting thousands of pounds of cow manure in open holding ponds, Joseph Gallo Farms uses it in a renewable energy technology known as a methane digester. However, because both Gallo Farms and another dairy with a digester, Fiscalini Farms, are located in the San Joaquin Valley, an area with some of the worst air quality the country, the programs are running into problems with federal air quality standards. The air district is consistently considered in “non-attainment,” which means they aren’t meeting the federal limits on air pollution.
While both dairies’ digesters are reducing one kind of pollution, greenhouse gases, they’re actually adding to another kind. http://blogs.kqed.org/climatewatch/2010/08/29/cow-power-not-cutting-it/