Poop power

Eat manure for money? Sounds gross, but that’s exactly what the bacteria at Tollenaar Holstein in Elk Grove are doing, and it’s paying off for owners Jon and Tami Tollenaar.

They’ve got 2,000 head of cattle on their 300-acre ranch, but not as many cow patties as you might think. That’s because much of the animal waste is processed in an anaerobic digester that converts cow manure into energy. Fuel produced by the machine feeds a generator that provides more than enough electricity for the dairy’s operations. Surplus power is sold to SMUD, and the proceeds now account for 5 percent of the dairy’s revenue.

The Tollenaar digester produces 1.5 million kilowatt-hours annually, or enough energy to power 180 houses in Sacramento. It’s one of only two such systems in Sacramento County. In addition to providing a financial buffer, the digester helps lessen the impact of the air and waste pollution caused by most dairy operations.

“They’re diversifying their operations,” said David Shabazian of the Sacramento Area Council of Governments, who’s working on the Rural-Urban Connections Strategy, an economic development project. “They’re no longer just a dairy, they’re also an energy producer. It’s a great example of being innovative in agriculture.”

California has the biggest dairy industry in the United States, with 2,100 dairies and some 1.7 million cows, which produce more than 65 billion pounds of manure annually. Some excess manure serves as fertilizer, but much of the waste runs off fields into waterways on the way to contaminating public-water supplies and aquatic habitats.

The digester system flushes manure into a containment lagoon, where a natural microbial process converts biomass into methane. The resulting “biogas” is cleaned, treated and used to fuel a generator, instead of being released into the atmosphere. That’s important, because after carbon dioxide, methane is the next most destructive greenhouse gas.

In addition, since more waste is processed instead of being dumped in the watershed, the digester also helps curb water pollution. Dairy cows act as a major source of nitrate pollution in groundwater and drinking-water wells, threatening the drinking water of millions of Californians. Additionally, nutrients in animal waste cause algal bloom, which uses up oxygen in water and contributes to “dead zones,” in which bodies of water cannot support aquatic life.

Here in Sacramento County, some 16,000 cows sit on about 50 dairies. The Cal-Denier Dairy in Galt was the first site to begin operating a digester, which produces 500,000 kilowatt-hours per year. Three other dairy farmers in the county are in discussions with SMUD to start digester programs, but this depends on whether these farmers can obtain enough grant money to pay for part of the capital cost, said Dace Udris, public information officer for SMUD.

Jon, a second-generation dairy farmer, and his wife began developing their digester in 2005, with help from the California Water Resources Control Board, as well as grants from the California Energy Commission and the U.S. Department of Agriculture Rural Development program, which funds investment in renewable energy and energy efficiency.

The couple struggled to get the project off the ground. The Sacramento Metropolitan Air Quality Management District wasn’t pleased that although the digester burns methane that would otherwise be released to the atmosphere, it also increases smog without the proper equipment. The Tollennars put a sulfur scrubber on the digester—which wasn’t cheap—and the local air-quality agency granted the couple the permit necessary to proceed.

The Tollenaars hope to continue operating the digester and eventually expand the material it can process. But that won’t be easy.

“We need the grants, otherwise the project wouldn’t be able to exist,” Jon said. “Right now, it’s manure only. One day, we want to bring in food waste.”