Review shows 23% boost in animal units.

The 8,000 Holsteins that make the feedstock for the $42 million Marshall Ridge Renewable Energy Center are barely visible — just a flash of black-and-white hide behind the screens of a confinement building in central Iowa.

But the nearly 200,000 gallons of manure the dairy cows produce each day feed three anaerobic digesters that capture methane — a potent greenhouse gas — from the manure and turn the gas into renewable fuel that can be sold for big-time profits.

“More cows and more manure means more energy,” said Karl Crave, vice president for operations at Dynamic Renewables, a Wisconsin company that owns and operates the Marshall Ridge center.

The Biden Administration has lauded on-farm digesters for reducing methane emissions from livestock, spending $200 million on projects across the country in 2021 alone. Large digester facilities can earn tens of thousands of dollars per day by pumping renewable natural gas to states like California with low-carbon fuel standards.

But critics say the climate benefit of methane capture from livestock is overshadowed by the potential harm caused by adding more animals — and their manure — in a state already plagued by water quality problems from farm runoff.

“If a farmer’s got 1,000 dairy cattle and he wants to put in a digester to generate natural gas to power his farm in some way, what do I care?” said Chris Jones, president of the Driftless Water Defenders and author of “Swine Republic: Struggles with the Truth about Agriculture and Water Quality.”

“If he puts in that digester and expands his herd from 1,000 to 5,000 and then is using public money to do all that and then it’s dressed up as some sort of climate change solution, I’m calling (an expletive) on that.”

The Driftless group has filed two lawsuits against Winneshiek County leaders for approving a digester facility in northeast Iowa, where porous karst terrain means pollutants can quickly contaminate private wells and prized trout streams. The Iowa Department of Natural Resources approved a permit for a digester at Full Bohr Farms Oct. 17.

Many digester sites boost herds

Iowa has permitted 15 new digester facilities since 2021, when the Legislature passed a law allowing animal feeding operations with digesters to exceed the state’s limit of 8,500 animal units.

Seven of the 15 dairy farms added to their herds since they got digester permits, a review of DNR data shows. When you add up all 15 Iowa sites, animal units went from 84,861 before the sites got their digester permits to 104,424 after — a 23 percent increase.

The largest increase was at Hoogland Dairy, in Sioux County, which more than doubled its maximum animal units from 3,000 to 7,860 after a digester expansion. Iowa now has three dairies with more than 10,000 maximum animal units. All the state’s new digesters are at dairy farms.

There’s concern more manure may mean bigger spills — like one that happened Feb. 7, 2022, at Winding Meadows Dairy in Lyon County in northwest Iowa.

More than 376,000 gallons of liquefied manure leaked from a digester into Lizard Creek, a tributary of the Big Sioux River. The spill happened before the state had granted a construction certification, so the operator should not have been pumping manure into the tanks. The Iowa Department of Natural Resources fined Terry Van Maanen, who owned the dairy whose cattle supplied the manure for the digester, $10,000.

“The manure release from the digester ultimately resulted in the degradation of water quality and causing an elevated pollutant level,” the DNR wrote.

Colorado-based Gevo, which operates the digester at Winding Meadows and digesters at two other large northwest Iowa dairies, said the company made changes after the incident. “Working closely with the DNR, we translated DNR approved process improvement measures across our operation,” spokeswoman Heather Manuel said in an email.

Van Maanen was cited twice after the February 2022 spill. In April 2022, the DNR found manure leaking from a tile line and in January 2023, 500 gallons of manure “foam” was released from the digester, but did not enter a waterway, according to DNR records reviewed for this story. Van Maanen said last month he has sold the dairy.

Winding Meadows did not immediately expand after the digester was built, but new owner Joel Bleeker got a permit in May to boost the herd 45 percent after a new calf barn is built.

There have been other violations at dairies with digesters:

• Maassen & Sons Dairy, in Sioux County, was cited in June 2023 for starting to build a digester without a permit. The DNR cited the dairy in November 2023 for building piping to transport manure without having a permit. Regulators again dinged Maassen & Sons in April for failure to submit quarterly reports. Maassen & Sons increased its herd by 23 percent in the last couple of years.
• Roorda Dairy, in O’Brien County, was cited in November 2021 for starting to build a sand separation system for a digester without a permit. Roorda’s herd size has not changed.
• Black Soil Dairy, in Sioux County, caused a fish kill in March 2023 when manure discharged from the dairy to Deep Creek, the DNR reported. Black Soil hasn’t increased its herd since getting a digester permit.

Marshall Ridge project

Marshall Ridge, which started operations near State Center in February 2023, takes manure from Kevin and Holly Blood’s dairy cattle, adds water and pumps the mix into one of three 1.3-million-gallon digesters.

Digester staff keep the manure at 100 degrees, providing a perfect environment for natural bacteria to break down the manure, Acting Facility Manager Michael Raymer said. The tanks are insulated against Iowa’s cold winters.

The process releases gas, including methane, that is collected from the top of the digesters and filtered to remove water vapor, carbon dioxide and hydrogen to create renewable natural gas. Black Hills Energy injects the compressed gas into the Northern Natural Gas pipeline that runs underground near State Center.

Government incentives for digesters

There are thousands of on-farm digesters in Europe, but U.S. development has been slow until state and federal incentives.

The Rural Energy for America Program provides loans of up to 75 percent and grants for up to 25 percent for renewable energy systems, such as digesters. The Inflation Reduction Act offers tax credits that would defray the initial startup costs.

A digester pilot project in Iowa and Missouri got $80 million from the USDA’s Partnerships for Climate-Smart Commodities in 2022. Most of the money is used to incentivize farmers in southeast Iowa and northern Missouri to plant prairie and cover crops that will be harvested and fed into digesters to produce renewable natural gas, explained Will Higgins, development manager with Roeslein Alternative Energy.

“We are focused on restoring over 40,000 acres of prairie and incentivizing over 40,000 acres of cover crops,” he said.

The digester facility near Stockton will process the biomass with cattle manure from Sievers Family Farm. Iowa State University will monitor, measure, record and verify goals for the project.

Cutting ag emissions

Iowa ranks No. 2, behind Texas, for greenhouse gas emissions from agriculture.

“Manure causes about 10 percent of U.S. methane emissions,” said Mike Helbing, staff attorney for Penn State University’s Center for Energy Law and Policy. “If these methane emissions are captured, it’s a great benefit for the environment.”

California is driving the development of anaerobic digesters across the farm belt. California requires fuel producers there to stay below certain carbon intensity thresholds or buy credits from low-carbon fuel producers in California or other states. If a digester facility in Iowa can supply Renewable Natural Gas to a pipeline that goes to California, the digester facility can sell its credits to California companies.

“If you’re producing RNG, even in the state of Iowa, you’re creating a renewable fuel that is generally going to come in lower (in carbon intensity) than State of California standard,” Helbing said.

The credits can bring the value of RNG as high at $100 per metric million British Thermal Units (MMBTU), but Helbing says $27 to $30 per MMBTU is a more likely value at this time.

The Marshall Ridge project produces 250 and 325 MMBTU of renewable natural gas per day. Gevo plans to produce 440,000 MMBTU of renewable natural gas a year at the northwest Iowa digesters, according to its website.

Some economists question whether anaerobic digestion from cow manure is worth the cost.

“Digester revenue has been substantially higher than the value to society of prevented methane emissions,” Aaron Smith, professor of Agricultural and Resource Economics at the University of California, Berkeley, wrote in an April 2023 analysis of the value of methane from cow manure. “This means that society is overpaying for these methane reductions. The cost is paid by producers of gasoline and diesel, who buy LCFS (low-carbon fuel standard) credits and pass the cost along to consumers in the form of higher fuel prices.”

Smith suggests dairy farmers pay the cost of reducing methane emissions.

The potential biogas from digesters at swine and dairy operations in the United States, according to a 2018 EPA report, is less than 1 percent of the total natural gas used in the United States in 2019, according to a report from the U.S. Energy Administration.

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