Gas to Gas: Dairy Manure Powers California Ethanol Plant

In a first for the Golden State, a dairy, a digester and an ethanol plant partner to create renewable energy.

California’s first biogas project connecting a dairy to an ethanol plant officially crossed the finish line last week with a public inauguration at its San Joaquin Valley site.

Nearly six years in the making, the $9.5 million renewable energy project relies on manure piped from a dairy a mile away to an anaerobic digester at the Calgren Renewable Fuels ethanol production facility in Pixley, Calif. 

Calgren’s digester captures manure-generated methane gas and burns it as clean biogas to power the ethanol plant. In turn, the plant yields nearly 60 million gallons of ethanol a year that, blended with gasoline, creates a low-carbon fuel for many of California’s 27 million cars.

Officials said the Pixley biogas project is the first California digester to use agricultural waste to create renewable natural gas to power another renewable energy facility. It’s also the first digester in the Golden State to be 100% American made and constructed. The plant now becomes California’s lowest-carbon commercial ethanol producer.

“This project is a model for biorefineries in California and throughout the U.S.,” Jim Mckinney, program manager for the California Energy Commission, said at the digester’s Feb. 10 grand opening. The state agency contributed $4.6 million in grant funds to the project.

The project produces several benefits, officials said.

The dried manure solids that are discharged at the back end of the digester cycle are trucked back to Four-J Dairy every day to be used as bedding for the herd.

“We turn waste into fuel,” said Calgren Renewable Fuels president Lyle Schyler, adding that ethanol comprises 10% of fuel at California’s gasoline pumps. Moreover, the project’s carbon output “is quite low,” because of the digester and other emission-controlling equipment at the plant. “This project is exceptionally green,” Schlyer said.

“Electricity and hydrogen are getting a lot of media attention these days as the fuels of the future,” said Mckinney. “But it is the workhorse plants like this Calgren facility that reduce the carbon content of our fuel supply. At 58 million gallons per year, that’s enough low-carbon fuel for 145,000 cars every year.”

The new biogas system will reduce the amount of natural gas used to fire Calgren’s boilers by 6% and reduce the carbon footprint of the plant’s fuel product by 67 grams of carbon per megajoule, added Mckinney. “That’s one third less carbon than gasoline and one third less carbon than most of the corn ethanol from the Midwest that we import,” he said.

The project’s benefits don’t stop with Calgren and the California environment. Frank Junio and his family also have profited from the project. It’s their Four-J Dairy that’s supplying the manure to Calgren’s plant. 

For their role in providing the manure, the Junios got a new manure management infrastructure for their 1,800-cow dairy operation.  That includes a double-lined lagoon.  

Frank Junio's dairy supplies the manure to the ethanol plant, seen in the distance.

The dairy also gets the dried manure solids that are discharged at the back end of the digester cycle. Those manure solids are trucked daily from the Calgren plant to Four-J Dairy, where they’re used as bedding for the Junios’ dairy herd. The digester’s remaining effluent is piped back to the dairy each day to be applied to field crops.

The Pixley biogas digester is a two-stage, plug-flow complete mix system. It has a 1-million gallon capacity, said Steve Dvorak, whose Wisconsin-based DVO company engineered the digester. (Calgren’s Daryl Maas conceived and guided the project; Regenis built the digester.) While 90% of the waste going into the digester comes from the dairy, the digester has received permitting to use all feed stocks, including municipal waste and food processing waste.

Located 12 miles south of Tulare and adjacent to Freeway 99, the Calgren facility was built in 2008. It’s one of only four commercial ethanol production plants in California. Corn feed stock for Calgren’s plant arrives by train from the Midwest at the neighboring JD Heiskell facility. It’s then transferred via elevators and conveyors to Calgren’s plant for processing. In addition to ethanol, the Calgren plant produces wet distillers grains and corn oil.