Storing carbon a mile and a half beneath Stanislaus County could help save the planet
A company seeks to drill two very deep wells in Stanislaus County to capture some of the carbon dioxide involved in climate change.
Aemetis Inc. would sink the wells at its ethanol plant in Keyes and another coming soon to Riverbank. They would be perhaps 8,000 feet deep, far below groundwater sources, and would store close to 40 million tons of compressed gas over 20 years.
The $250 million project would put the county at the forefront of the effort to sequester CO2 that otherwise would trap heat in the atmosphere. Experts say climate change is already disrupting agriculture, raising sea levels and making storms and wildfires more extreme.
Aemetis, based in Cupertino, hopes to complete its wells by 2024, co-founder and CEO Eric McAfee said in a phone interview last week. The company needs permits from the U.S. Environmental Protection Agency, including safeguards against leakage.
The Keyes plant has made ethanol for cars and trucks from Midwestern corn since 2011. The other plant is set to open in 2024 in the former Army ammunition plant in Riverbank. It will produce jet fuel from orchard trees and other wood waste in the Central Valley.
Ethanol has modest climate benefits compared with fossil fuels if it is simply burned in an engine, releasing carbon dioxide back into the air. Aemetis plans to strip CO2 during the fuel-making process and sequester it permanently in rock formations.
“It makes the value of our biofuels much higher and the benefits to the environment much higher,” McAfee said.
The wells also could take CO2 from oil refineries, cement makers and other industries hoping to meet climate goals. The gas could be delivered by truck, or by the railroads already serving Riverbank and Keyes.
Few such wells so far
Carbon storage wells require Class VI permits from the EPA. Only two have been approved to date, both at a corn processing plant owned by Archers Daniels Midland in Decatur, Illinois.
Fifteen other permits are pending around the nation, according to the EPA website. The California projects are all in Kern County: San Joaquin Renewables plans a well near McFarland as part of a plant turning nut shells and other ag waste into fuel. A company named Carbon TerraVault proposes to store CO2 from various industries in depleted petroleum deposits in the Elk Hills.
An application for a well in the Mendota area of Fresno County has been withdrawn, the EPA website said. It was proposed by Chevron and three partners at an idle wood-burning power plant, but drew opposition from activists.
Such wells run the risk of leakage, and they distract from the need for energy sources that involve no burning at all, said a December 2021 guest opinion in The Fresno Bee. It was by Rocio Madrigal, a community outreach worker for the Central California Environmental Justice Network.
“Allowing carbon storage in the Valley would be another example of environmental racism, where profits of companies like Chevron would be considered more important than the residents’ health and well-being,” she wrote.
People can ingest CO2 in moderate amounts — it’s what makes beer and soda fizzy — but excessive amounts can make aquifers too acidic. And leakage into the air would defeat the purpose of countering climate change.
Layers of sand and shale
McAfee said Aemetis experts have determined that CO2 could be injected into a sandy layer surrounded by impermeable shale about 7,000 to 8,000 feet down. That layer holds salty water from the time when the Valley was an inland sea.
The EPA has had discussions with Aemetis but not yet received formal well applications, regional press officer Joshua Alexander said by email Friday. Once received, the agency staff will review the plans and possibly issue draft permits for public comment.
The permit process includes drilling a test well to confirm the conditions underground. The permanent well must have casings on the shaft and other measures to guard against leakage into other geological layers. The site must be monitored throughout its operating life and after closure.
Alexander said such wells are “a relatively new technology and, as with any injection activity, there is a potential risk for the injected fluids to migrate and impact drinking water aquifers or cause other environmental and human health challenges.”
The Valley’s water wells reach a few hundred feet beneath farms and cities. They have casings and other safeguards against contamination by pathogens and chemicals.
Two million tons a year
The Riverbank and Keyes wells would each take in close to 1 million tons of CO2 per year. That’s just 0.006% of the worldwide carbon emissions from energy use in 2019, according to the U.S. Geological Survey.
Carbon also can be captured in live plants, including trees and vines on Valley farms, and in soil managed to build up organic matter.
Forests in the Sierra Nevada are dense with wildfire fuel that can spew massive amounts of CO2 into the air. A consensus has emerged around thinning them out to leave larger trees that continue to capture carbon as they grow.
The climate crusade also entails using energy more efficiently and getting more of it from solar, wind and other non-carbon sources.
Aemetis has taken on another climate-harming substance: the methane in dairy cattle manure. The company just started extracting it at several farms and piping it to Keyes for refinement into gas for PG&E lines and truck fueling. The process still emits some carbon but is less harmful than letting methane drift to the atmosphere.
This story was originally published July 19, 2022 at 6:00 AM.
