Happier cows are the reason California dairy farmers give for why they believe their cheese is better, but those tastier curds come with an environmental cost in the form of high methane emissions.

Agriculture accounted for 54% of the state’s 39.9 million metric tons of carbon dioxide equivalent in methane emissions during 2017. Manure management made up 26% of the state's methane emissions, according to the California Air Resources Board (CARB).

But oil and gas supermajor Chevron is working with dairy farmers in the state to address this problem with a solution that it hopes will become a viable, growing business. They are working to capture the raw biogas from manure and purify it into renewable natural gas (RNG) to use as an alternative fuel for heavy-duty trucks and buses.

Milestone achieved

California-based Chevron USA, California Bioenergy (CalBio) and local dairy farmers on Friday said their joint venture, CalBioGas, successfully achieved first RNG production from Kern County dairy farms.

"The Kern County project includes a feedstock comprised of about 80,000 cows, each producing an average of 80 pounds of manure each day," a Chevron spokesperson told Upstream in response to questions about the project. "With 1.8 million cows in California on more than 1,500 dairy farms, there is tremendous potential for growth."

The dairy industry has worked with state and local governments to identify and deploy such measures to dramatically lower the emissions from manure management.

Purifying biogas

Manure storage on dairy farms results in the release of methane. However, in the CalBio-designed process, the manure is flushed from collection areas into a solids separator before then flowing into a covered anaerobic digester. Microorganisms in the digester break down the organic matter, releasing biogas, mostly methane, that is then trapped in the digester, said CalBio.


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This raw dairy biogas is sent to a centralised processing facility where it will be upgraded to RNG and injected into a local pipeline of Sempra Energy’s gas utility SoCalGas, Chevron said. The RNG is then marketed as an alternative fuel for heavy-duty trucks and buses.

Vehicle fuel

Chevron announced the joint venture in June 2019 when it partnered with the digester designer and local dairy farmers to fund the construction of 18 digesters across three geographic clusters in Kern, Tulare and Kings counties. The company is also providing the services to bring RNG into the California vehicle fuels market, Chevron said.

“Chevron is increasing RNG in support of our business and is making targeted investments and establishing partnerships, as we evaluate many emerging sources of energy and the role they will play in our portfolio,” said Andy Walz, president, Chevron Americas Products, in a release.

The company's participation in the joint venture helps Chevron comply with the state's Low Carbon Fuel Standard (LCFS), which is designed to reduce greenhouse gas emissions in the transportation sector. The LCFS creates financial incentives to support the switch from carbon-intensive gasoline to other fuels like biomethane, according to CARB.

In addition, the project helps dairy farmers meet regulations passed in 2017 that require a 40% reduction in manure-related methane emissions from 2013 levels by 2030.