State officials say dairy digesters can reduce greenhouse gas and toxic air emissions from large dairies. Why community activists don’t believe them.
Driving along a rural road in the San Joaquin Valley on a blistering afternoon in mid-July, dairy farms and the fields of corn that feed their cows stretch as far as the eye can see.
As heat shimmers up from the desolate roads on the outskirts of Pixley, about 150 miles northwest of Los Angeles in Tulare County, the stench of cow manure fills the car, even with the windows closed tight to trap the air conditioning.
Tulare County, famous for having more cows than people, is the primary driver of California’s dairy industry, which adds about $20 billion a year to the state’s economy and supports 129,000 San Joaquin Valley jobs.
Dairies also contribute a substantial proportion of California’s greenhouse gas emissions. And Pixley is at the vanguard of the state’s efforts to reduce emissions of the climate super-pollutant methane from dairy farms.
California has invested millions in dairy “digesters” to meet its climate goals, among the most ambitious in the country. State officials say digesters, which capture methane gases from cow waste, are the most efficient way to mitigate dairy emissions. They reduce not only methane and the toxic emissions that go with it but also the environmental footprint of large dairies, officials say.
But community advocates say there’s no evidence that digesters provide environmental benefits for Pixley—or for other communities like it, where poverty and pollution are rampant.
And even if there are local benefits, advocates argue, the state’s approach to funding digesters endangers other disadvantaged communities by letting nearby oil companies and other polluters pay for their excess emissions instead of reducing them.
Studies over the past few years show that digesters are not even capturing all the methane at dairies that are using them.
Digesters work by covering vast open-air manure pits with tarps that look like massive gymnastic tumbling mats. The tarps expand like a balloon as they trap “biogas,” composed mostly of methane and carbon dioxide, for conversion into usable energy.
State and industry representatives tout the captured biogas as a renewable energy source that will power vehicles and feed the grid, helping California reach its daunting goal of reducing all of its greenhouse gas emissions to 40 percent of 1990 levels by 2030.
The state has spent nearly $300 million on grants to reduce dairy methane emissions, mostly on digesters funded partly through its pay-to-pollute climate policies, to the frustration of environmental justice advocates.
California is banking on digesters because methane, known as a short-lived climate pollutant, or SLCP, traps about 86 times more heat than carbon dioxide over a 20-year period, even though it dissipates much faster. Reducing methane and other SLCPs can bring immediate benefits and help buy time for the state to reach its target.
But the state is falling far short of its dairy methane emissions-reduction goal, a June report from the California Air Resources Board, which oversees climate programs, revealed. To reach it, the state will need to add at least 210 more digesters, among other measures.
Now the dairy industry and environmental justice advocates are locked in a battle over digesters rooted in advocates’ objections to state officials’ failure to take their concerns about the unequal impacts of its climate policies seriously.
“There’s a disconnect between the state’s approach to climate change and the view from the streets,” said Jonathan London, who directs the University of California, Davis Center for Regional Change.
“If community members don’t see clear evidence of benefits,” London added, “they’ll try to slow things down until they have better answers.”
Counting on Digesters
California has the nation’s biggest dairy industry. It produces about 20 percent of the country’s milk—and close to half of the state’s methane emissions.
The average dairy cow can produce about seven and a half gallons of milk a day and about 120 pounds of manure. Most large California dairies flush all that manure into vast lagoons, where microbes that thrive in oxygen-free environments break down organic compounds, releasing copious quantities of methane.
Cow burps also release methane, a byproduct of the way microbes make the ruminants’ food digestible. But state law prohibits regulations on cow burps until cost-effective, safe methods to capture belched methane become available, a result of pushback from the state’s powerful dairy industry.
So the state has focused on digesters, which can cost millions of dollars each and require private matching funds, making them unrealistic for small farmers.
Many of the largest dairies, known as confined animal feeding operations, or CAFOs, are located in rural, low-income communities of color like Pixley. Only 70 of the roughly 1,100 dairies in the southern San Joaquin Valley, the heart of the state’s industry, have fewer than 500 cows.
The dairy industry and some scientists who study dairy practices say digesters will make even the largest operations sustainable by capturing methane and converting it into usable energy. Biogas can generate electricity, fuel vehicles and power the grid, just like fossil fuel gas but without the carbon pollution, they say.
“What the program does is it takes a pollutant and converts it into an environmental asset,” said Stephen Kaffka, an extension agronomist at the University of California, Davis, who evaluated dairy digesters for CARB.
Although burning biogas releases carbon dioxide, keeping methane from entering the atmosphere makes up for that because it is so much more effective at trapping heat than carbon dioxide.
But critics call biogas a misguided solution to the climate crisis because it can supply only a fraction of current fossil fuel demand. It distracts from developing zero-emission clean energy sources like solar and wind, and will still release methane through the leak-prone natural gas pipelines that carry it. And if biogas producers forgo clean electricity generating options like fuel cells in favor of cheaper internal combustion engines, they’ll release carbon dioxide and harmful air pollutants in the process.
Matthew Botill, assistant division chief of CARB’s Industrial Services Division, said the state has responded to such concerns in part by encouraging digester projects that inject upgraded biogas into pipelines to minimize concerns about local air quality impacts.
But that’s not enough for environmental justice advocates, who believe the state’s focus on digesters to capture methane from vast lagoons is inherently unsustainable and unjust.
“It entrenches the industry’s worst practices,” said Tyler Lobdell, an attorney with Food and Water Watch, which joined other groups that recently urged Gov. Gavin Newsom and legislative leaders to end subsidies for large dairy farm biogas production.
Those practices, he said, are already harming communities throughout the valley and beyond.
Waiting for Proof
Elena Saldivar, a retired teacher and mother of five, has spent most of her 60-some years in Pixley, where more than a third of the town’s 3,300 mostly Spanish-speaking farmworkers live in poverty.
She knows it’s hard to pinpoint the cause of any one person’s health problems. All she knows is that when her grandson moved to Pixley several years ago after his parents split up, he developed asthma.
“Once he came here he definitely had more health issues,” said Saldivar.
Saldivar has spent years trying to hold state officials accountable for all the environmental hazards plaguing her community.
The San Joaquin Valley air they breathe is among the worst in the nation, yet for years state regulators delayed action to control pollution from crop burning and oil and gas operations in the region. And decades of lax oversight of the state’s agricultural industry left hundreds of water systems in poor, unincorporated valley towns paying, even now, for tap water that’s tainted with nitrates from applying manure and fertilizer to crops.
A decade ago, after she retired and her kids were grown, Saldivar volunteered for the town council with high hopes of shaping local development projects.
Then she learned about a state-funded plan to build a biogas plant in Pixley, just a week before a county vote on the project. It would end up being the state’s first facility to process biogas sent via pipeline from a cluster of dairies. She felt blindsided.
“They didn’t even run it by us,” Saldivar said, reflecting a sentiment widespread among environmental justice advocates that communities have no meaningful voice in California’s climate policies.
If the state wants community members to believe that digesters are improving the region’s miserable air quality, Saldivar said, they should have installed air monitors.
“Why aren’t they doing that? That’s accountability to me,” she said. “I want to know, what is the true impact?”
Methane does not directly pose health risks, but is often accompanied by releases of particulate matter, ozone and other “co-pollutants” that do cause harm.
The ozone triggered by methane releases, for example, contributes to asthma and other serious respiratory problems. Tulare is the fifth most ozone-polluted county in the United States, according to the American Lung Associations latest State of the Air Report.
In theory, a well-managed digester should capture methane and harmful co-pollutants from manure, bringing substantial air quality and health benefits to Pixley and other towns blighted by air and water pollution.
The state has not required monitors on digesters to prove this is the case, however.
Lyle Schlyer, president of Calgren Renewable Fuels, which runs the Pixley biogas plant, believes they’re capturing all the methane that otherwise would have been emitted.
“It would really just be a failure if we didn’t get everything,” Schlyer said. “Our job is to get everything.”
Yet a 2019 Nature study shows that digesters aren’t foolproof.
“We definitely saw methane emissions coming from digesters,” said study coauthor Francesca Hopkins, an environmental scientist at the University of California, Riverside’s Greenhouse Emissions Lab. “We know that there are leaks.”
Using aerial imaging technology, researchers found “fairly persistent” methane plumes coming from four San Joaquin Valley digesters on different days. Two of the digesters were about 15 miles northwest of Pixley.
The leaks don’t trouble Kaffka, who evaluated digesters for CARB. “Even if you have some leakage, it’s way less than the open emissions from the lagoon,” he said.
But without monitors on the digesters it funds, the state can’t provide evidence of community benefits, said Julia Jordan, policy advocate for the nonprofit Leadership Counsel for Justice and Accountability.
“We’re seeing a lot of claims that are not only based on really unclear measurements but also overestimating the reduction benefits of digesters,” Jordan said.
Getting Ahead of Regulations
California has other options besides investing in digesters for large dairies with massive manure lagoons, environmental justice advocates say.
The state should instead pursue strategies that prevent methane from forming in the first place, Lobdell, of Food and Water Watch, said.
He added that investing in alternative manure management programs that encourage pasture grazing and aerating waste would help the industry transition to more just and sustainable farming systems.
Michael Boccadoro, a lobbyist and executive director of Dairy Cares, an industry group, said that pasture-based dairy farming is not well suited to the San Joaquin Valley because it uses too much water. “We cannot get to the reductions the state is asking for with pasture-based dairies or alternative manure management,” he said.
Boccadoro said he sees digesters as the most practical way for dairies to reduce methane emissions, and is frustrated that critics call biogas greenwashing. “To me, taking dairy manure and turning it into clean-burning transportation fuel is not greenwashing,” he said. “It’s amazing to be able to do that.”
Manure from more than 47,000 cows supported eight Pixley digesters in 2019, according to Maas Energy, which develops the technology.
Joey Airoso, a fourth-generation farmer in Pixley with several thousand cows, was among the first to install a digester on his property.
“We’re always looking for new technology, ways to be more efficient, ways to protect the environment,” said Airoso, whose family has raised dairy cows here since 1912. “Even before the regulation came down the pike, we were looking at ways we could generate energy with the gas.”
California’s dairy-methane program and digesters, he said, offered an opportunity for him to “catch the gas and do something good with it.”
Biogas captured on Airoso’s farm, along with methane gas from nine other Pixley dairies, travels through 29 miles of underground pipeline to Calgren Renewable Fuels, at the north end of town.
Crews are installing digesters at seven more local dairies, said Calgren’s Schlyer. A dozen other clusters are operating around the San Joaquin Valley.
Calgren removes impurities from the biogas so it can be used as fuel for trucks to replace dirty diesel. “The highest incentives are to put it into compressed natural gas, a vehicle fuel, to reduce air pollution in the Central Valley,” Schlyer said.
By incentives, Schlyer means the “offsets” offered through California’s low-carbon fuel market, where companies that reduce carbon dioxide emissions sell credits to those that don’t. Dairies and biomethane producers like Calgren can sell those credits to help underwrite capital costs associated with digesters and biogas processing.
The state requires digester projects to use captured methane for energy production or transportation fuel like compressed natural gas. It does not track how many biogas projects replace diesel trucks, however, or reveal which companies avoid reducing their emissions by buying low-carbon fuel credits. The state protects buyers’ and sellers’ identities as confidential business information.
Testing Claims, at Last
Revenues from California’s market-based programs have made dairy digesters one of the most efficient ways to reduce methane emissions, state officials say.
But that efficiency, environmental justice advocates counter, comes at the cost of dumping even more pollution on neighborhoods already shouldering the burden of hazardous industrial operations.
That’s because California’s market-based climate policies allow polluting companies like power plants and oil companies to buy offset credits rather than reducing emissions at the source. The first study to evaluate potential disparate air quality impacts of California’s climate policies, published in 2018, found that emissions of greenhouse gases and co-pollutants from industrial facilities were more likely to increase in disadvantaged neighborhoods with more than their share of pollution.
The state’s dairy digester program has been funded partly through offsets purchased by some of the biggest polluters in California, including Tesoro, an oil refining company that spent millions to fight state climate policies and that California researchers once ranked “worst in health impacts among all companies with refining operations in the state.”
Officials are so focused on reducing emissions they aren’t always willing to take a hard look at potential negative consequences, said London, of UC Davis.
There are clear health burdens for people living near CAFOs, said Joan Casey, an environmental epidemiologist at Columbia University who published a review of those harms for Global Environmental Health and Sustainability in 2015.
People living near the facilities experience stress, cognitive problems, asthma and impaired lung function, among other health issues, Casey said.
There’s a dearth of studies on potential health effects of digesters, however.
It makes sense that covering lagoons will trap harmful emissions like ammonia and volatile organic compounds, Hopkins said, but it needs to be tested. Plus, that doesn’t affect emissions from cattle feed and other parts of the dairy that contribute to particulate matter and ozone pollution, which aggravate asthma and other respiratory problems.
Are digesters ultimately benefiting communities? “I think the jury’s still out,” Hopkins said.
Hopkins and another research group are in the process of getting answers from the kind of studies community activists have long clamored for.
The Electric Power Research Institute, a California-based public interest nonprofit, won a grant last year to test whether projects that produce biomethane from digesters and other technologies effectively capture methane and its co-pollutants from waste, noting that “only limited data exist from real-world operating facilities.” EPRI scientists will take detailed measurements before and after projects like digesters are implemented to generate renewable natural gas for use in pipelines.
For her part, Hopkins is focused mostly on methane. She partnered with a “typical” area dairy, and started monitoring methane emissions on its open lagoon through each season in the fall of 2018. She wrapped up in January 2020, right before the pandemic took off. Since then, the dairy, which Hopkins won’t reveal to protect the farmer’s privacy, has won a state grant to install a digester.
“We’re going to repeat those same measurements now that there’s a digester there, using the same methods,” Hopkins said. “It should be as apples to apples kind of a comparison as you can get.”
She said she sympathizes with dairy farmers, recognizing that it’s onerous for them to host a scientific study. “But this data is desperately needed,” Hopkins said.
“We have these strong laws about reducing these gases,” she said. “But if we don’t make measurements to actually verify that emissions are going down over time, then our laws are meaningless.”
Hopkins said she also understands why communities are concerned. “We just don’t know enough right now to say anything conclusively.”