California district considers anaerobic digester

By Ryan C. Christiansen
Web exclusive posted August 29, 2008 at 1:42 p.m. CST

The South San Joaquin Irrigation District, which provides irrigation water for the agricultural areas surrounding the cities of Escalon, Ripon, and Manteca, Calif., has begun a feasibility study to determine if the district should build an anaerobic digester to assist area dairy farmers, as well as produce and sell electricity. SSJID is considering a proposal to build a digester for Brasil & Sons Dairy Inc. in Escalon, which has 2,850 cattle that could supply feedstock for the facility.

Because the San Joaquin Valley has air quality problems and dairy operations contribute to greenhouse gas emissions, building an anaerobic digester in the district is not a new idea for the area, according to Jeff Shields, general manager for SSJID. There are as many as 120,000 head of cattle in the valley that contribute to the problem, he said. "Our interest is in helping dairy farmers deal with that," Shields said. "To the extent that any of those facilities individually or collectively might represent 700 to 1,000 head of cattle, it might make sense for anaerobic digestion to be developed here."

However, the SSJID needs to be sure that the project makes economic sense, he said. "We just have to figure out what role we will play in that," Shields said. "We've got capital, we've got time, and we have an interest in (power) generation, and power costs are outrageous in California. Our goal would be to recover our investment and to generate electricity locally."

The district has provided irrigation water from the Stanislaus River to 72,000 acres of farmland in southern San Joaquin County since 1909. Now, the district is moving towards becoming an electric utility, as well, Shields said. The district has been selling wholesale hydroelectric power for half a century and wishes to purchase the local electrical distribution system from Pacific Gas and Electric Co. SSJID produces approximately 130 megawatts of hydroelectric power and one megawatt of power from an array of tracking crystal solar panels, he said.

"The board has a fundamental policy of keeping money local," Shields said. "The more generation we can own locally and distribute throughout our service territory, the better we're going to be. Every time you buy an electron from Pacific Gas and Electric, there is a sucking noise-and that's dollars heading to San Francisco."