California dairies face uncertain future for digester development

July 27, 2008 07:00 PM

Conflicting air-quality regulations are making it increasingly difficult for California dairies to build methane digesters, a state dairy leader said Thursday.


Michael Marsh, CEO of Western United Dairy and its subsidiary Western United Resource Development (WURD), sounded a cautionary note about constructing additional digesters in the state as elected officials, government agency representatives, engineers and dairy producers gathered in southern Sacramento County to celebrate the latest opening of a dairy digester.


"This may be one of the last digesters built in California because of conflicting regulations between AB32 [the state's new global warming legislation] and new regulations coming out of air districts with regard to emissions from the engine generator sets,” Marsh told the crowd gathered at the Cal-Denier Dairy.


The air districts have set a standard for emissions from "these types of engines that have not been achieved by any engine manufacturer anywhere in the world,” said Marsh. "Unfortunately, air district regulations do not take that fact into consideration nor are they allowed to take into consideration the benefit derived from combustion of methane from digester projects. Policy makers have to clear a pathway for renewable energy opportunities to be realized.”


The conflicting regulations are causing frustrations for dairy producers who are committed to being responsible environmental stewards, said Marsh. "Farmers want to do their share to enhance sustainability, and it's frustrating when two different regulations run at cross purposes with one another,” he said.


The project uses manure from the dairy's 500 milk cows to provide renewable power for the Sacramento Municipal Utility District (SMUD).


In addition to providing renewable energy, the new digester captures methane emissions—a greenhouse gas 22 times more potent than CO2 in causing global climate change, Marsh said. Cal-Denier uses a flush manure-management method to keep the stalls clean. The dairy's new digester is an ambient-temperature covered lagoon digester designed by RCM Digesters.


Digester funding was provided by WURD, SMUD, the USDA Rural Development Program, and the USDA Natural Resources Conservation Service. The approximate capital cost of the digester system is $700,000 with an anticipated pay-off of seven years.


Catherine Merlo is Western editor for Dairy Today. You can reach her at


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