SMUD wants to be carbon-free by 2030. Should it capture carbon and store it underground?

In a project that would be the first of its kind in the country, the Sacramento Municipal Utility District is considering a proposal to capture carbon emissions from a natural gas power plant and deposit them deep underground.

Calpine Corporation, one of the nation’s largest producers of natural gas and geothermal electricity, is appealing to SMUD to develop carbon capture and storage technology at the Sutter Energy Center, a gas plant outside Yuba City.

The project involves taking carbon dioxide generated by burning fossil fuels and transporting it half a mile into the earth for permanent storage, with a goal to reduce atmospheric greenhouse gases that trap heat and cause climate change.

As SMUD vies to eliminate carbon emissions by 2030, proponents of CCS say it will help preserve reliability while achieving that goal. California has also called for the capture or removal of about 100 million tons of carbon per year to reach carbon neutrality by 2045.

But the relatively new technological process has yet to win wide acceptance, particularly in the electricity sector where carbon-free alternatives like solar and battery storage are abundant. Critics, meanwhile, warn of unknown environmental consequences and argue that carbon capture merely prolongs the life of fossil fuel facilities.

Gas comes up, carbon goes down

In an initial presentation to SMUD’s board last month, Calpine pitched the venture as a unique opportunity that could take advantage not just of California’s geology, which is ideal for storage, but also substantial government subsidies.

New machinery would include a tall tower that, through a chemical process, separates carbon from the facility’s exhaust. Carbon is then compressed and sent more than half a mile underground by pipeline into layers of porous rock for permanent storage.

The project would capture as much as 95% of carbon emitted at the facility, which produces 550 megawatts of power a year, representatives said. It would sequester up to 1.5 million metric tons of greenhouse gas emissions annually.

Calpine estimated the project’s completion by January 2027.

“We look forward to engaging in a dialogue about this technology and the project with SMUD customers and residents of Sutter County as we move through the permitting process,” Calpine spokesperson Brett Kerr said in a statement.

According to a study by the Lawrence Livermore National Laboratory, much of California’s underground geology, with its ample layers of porous rock, is well-suited for carbon storage. Using oil and gas industry data, researchers estimated the Central Valley alone can store 17 billion tons of carbon.

George Peridas, director of carbon management partnerships at the research lab, said some carbon storage projects pose the risk of man-made earthquakes triggered by leaking pipes. But the risk is minimal in this case, he said, and regulations are strong enough to keep carbon from escaping.

“This is not a major technological breakthrough, but I think it would be a breakthrough in the quest for California carbon neutrality because we’re going to need these projects,” Peridas said. “These pilot projects...they are real-life examples of what we have to replicate many times over.”

SMUD has said clean energy sources can bring its power supply to 90% zero carbon, but that it needs technologies such as carbon capture and sequestration to achieve the last 10%. To preserve service reliability during heat waves or other extreme weather events, its plan calls for carbon capture to make up the difference.

“The proposed project holds potential due to the technology, location, geology and potential to be a reliable power source in an existing location while accelerating carbon reduction,” said Bryan Swann, SMUD director of resource strategy, in a statement.

‘Worst nightmare’

Katie Valenzuela, senior policy advocate with the Central Valley Air Quality Coalition and a Sacramento City Council member, is concerned about the proposal and disappointed by SMUD’s response after years of advocating for skepticism of carbon capture technology in the state legislature.

She said lawmakers led her to believe CCS projects would be deployed only where necessary, in hard-to-decarbonize industries like cement production, and not in the power sector.

The lab science may not be new, she said, but we have little way of anticipating the environmental and public health impacts of this technology. CCS technology would also do very little to reduce environmental harms suffered by those who live near gas plants.

“This technology and the claims they’re making is an unfortunate delay on the real climate action that we want to take,” Valenzuela said. “I’m seeing my worst nightmare come to reality, which is that this technology is going to be used to prolong a natural gas power plants that I do not believe should continue to be in operation.”

Calpine said it is taking steps to test the carbon capture and storage technology on a pilot project, but even the Livermore study said more research assessing carbon pipelines’ long-term ability to prevent leakage is needed.

This project may not be as needed as other industries, but there are obvious reasons why an electricity company would pursue it anyway, said Danny Cullenward, policy director for CarbonPlan.

“Part of what makes this complicated is there’s very generous federal tax credits for CCS,” he said. “Those are so lucrative, I think they could kind of pull some projects that might not otherwise seem like the most sensible thing and make them look attractive.”

SMUD plans to hold a public workshop to discuss carbon capture and sequestration in April. A project update and final decision on the project by the board is expected in May.