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Cellulosic ethanol plant is retooled for renewable natural gas

Verbio North America says it will more than double the capacity of its plant in central Iowa to produce renewable natural gas from corn stover, and it plans to begin production of corn ethanol in the final months of the year. The facility was the first of three plants in the nation to return to biofuel production after faltering as a producer of cellulosic ethanol, made from grasses, woody plants, and crop residue.

Seaboard Corp. is building a renewable diesel plant at the site of a former cellulosic plant in Hugoton, Kansas, with the facility expected to be ready for production this year. POET, the largest U.S. ethanol producer, stopped production of cellulosic ethanol at its Project Liberty plant in northwestern Iowa in 2019, and said it would use the facility for research to lower the cost of producing clean-burning, second-generation biofuels.

The Verbio plant, described as the first industrial-scale renewable natural gas facility using agricultural residues in the country, began injecting gas into Alliant Energy’s pipeline network in early December, said company officials. Production was running at a rate of 7 million ethanol gallons equivalent (EGE) and would rise to 19 million EGE in the final months of this year, when the plant also will begin production of corn ethanol at an expected rate of 60 million gallons a year. Verbio said it spent two-and-a-half years on “transformation” of the plant.

Renewable natural gas is created through anaerobic digestion of shredded corn stover in large vats for 20 to 60 days, says Verbio. The raw biogas contains 45% carbon dioxide and 55% methane. “Carbon dioxide and other impurities are removed through a biogas treatment process, leaving nearly pure biomethane gas, which is chemically equivalent to fossil natural gas.”

So-called advanced biofuels, such as cellulosic ethanol, have been slow to come to the market. The EPA estimates 4.6 billion gallons were produced in 2020, with biodiesel accounting for 2.4 billion gallons. It estimated cellulosic biofuel production at 510 million gallons. Most of the cellulosic fuel was derived from landfill and wastewater treatment plants, said Verbio.

“With the right policies, there is a tremendous untapped source of agricultural residue feedstock available for renewable fuels,” said Claus Sauter, chief executive of Verbio, based in Germany.

Farmers were paid $8 for each large, square bale of corn stover sold to Verbio, said an Iowa State University release. “The company contracted about 6,000 acres this year and hopes to expand to 30,000 acres in 2022.” ISU said “Verbio typically removes about 50% of the corn stover” per acre. “In addition to natural gas — the primary product — the process yields a nutrient-rich by-product called humus, which serves as a soil amendment and organic fertilizer.”

In full operation, the Verbio plant in Nevada, about 35 miles north of Des Moines, would consume 100,000 tons of stover per year. The original owner of the Nevada plant, DuPont, expected to use corn stover to produce cellulosic ethanol.

Produced with FERN, non-profit reporting on food, agriculture, and environmental health.
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