Manure digesters face impossible task

Manure digesters in California are facing the strictest regulation yet. The San Joaquin Valley Air Pollution Control District is mandating an emissions standard of nine parts per million Nitrogen Oxides or NOx that existing digester technology has never conclusively met. NOx combines with volatile organic compounds to form ozone, and the Air District has been faced with the challenge of reducing all NOx emissions. 

New and existing digesters would have to add air pollution control technology to engine generators or face forced shutdown. “This means huge up front costs and expensive operating and maintenance costs,” says Allen Dusault with Sustainable Conservation. Digesters could still be operated and gas flared, but no electricity produced. The purpose of the digester would be defeated. 

The Air District’s determination comes shortly after a ground breaking decision by utility companies to allow dairy producers to sell excess electricity back to the grid for over nine cents a kilowatt hour. Dusault is working with the Air District to resolve the emissions level.