Renewable Natural Gas From Corn Stover

by Chris Clayton (DTN Progressive Farmer) Failed Cellulosic Ethanol Plant Became North America's Largest RNG Producer -- When DuPont shut down its cellulosic ethanol plant in 2017 after years of effort and $225 million in investment, it looked like the process of converting corn stover to renewable energy was a failure.

In 2018, Verbio North America Corp., a subsidiary of Verbio Vereinigte BioEnergie AG in Germany, bought the plant from DuPont and began its conversion. Verbio, though, wasn't looking at cellulosic ethanol, but saw an opportunity instead to convert corn stover to renewable natural gas (RNG).

"We were never interested in the cellulosic ethanol portion of things," said Holly Schnur, director of marketing and communications for Verbio North America. "At the time, the economics of it just did not make sense, so the intent was always to bring the RNG technology from Germany over."
...

While other renewable natural gas (RNG) producers are converting dairy manure or landfill waste into RNG, Verbio is using about 100,000 tons of corn stover in its process, making it a unique producer for RNG in the North American market. Verbio now champions the facility as North America's largest industrial renewable natural gas plant.
...

Under the Renewable Fuels Standard, RNG can qualify as an advanced biofuel and qualify for both D-3 and D-5 Renewable Identification Number (RIN) credits. In California's low-carbon fuel standard (LCFS), renewable natural gas has one of the lowest carbon-intensity (CI) scores of any fuel.
...

In May, Verbio also bought South Bend Ethanol in Indiana and announced a $230 million upgrade for the plant. Verbio will follow the process set up in Iowa to produce 2.8 billion cubic feet of RNG in Indiana and 85 million gallons of ethanol production as well.
...

Verbio started processing RNG in late 2021 from stover stacked up around central Iowa for the DuPont facility. Verbio built two stover buildings that combined can store more than 100,000 bales. This year, the company stated it has signed contracts with farmers for at least 26,000 acres to collect stover from the fields.

Schnur noted Verbio doesn't clean cornfields of residue, but takes one-third to half of the stalk residue on the field, leaving some substantial carbon and erosion reduction in place.
...

While a typical ethanol plant will produce dried distiller's grain for livestock feed, Verbio won't dry the distilled grain but will instead feed it to a second set of digesters to produce more RNG. Verbio plans to use that strategy in both the Iowa and Indiana plants. The end result will also be a liquid fertilizer by-product that Verbio will end up marketing.

Another byproduct from the methane digestion is tons of humus that looks just like a mulch product people buy at a gardening store. Verbio is starting to offer the humus as a soil conditioner for producers in the area, especially those who provide stover. Schnur said Verbio staff are trying to educate farmers about the benefits of applying the humus to their fields.

Trying to introduce the humus to producers, Verbio will truck and spread it for $22 a ton and producers with trailers can pick it up at the plant for $7 a ton.

"It has all of the same N, P and K values that come off the corn stover. It's essentially the equivalent of what came off the field, but it's in a much more usable form," Schnur said.
...

The group called the RNG coalition cites there are now 281 operation RNG facilities around the country with another 180 under construction and 296 on the drawing board. If all come to fruition, there could be more than 750 RNG facilities before the end of the decade. In comparison, there are about 200 ethanol plants nationally. Most RNG facilities now capture methane from municipal waste landfills, but dairy and swine operations are growing as well.

The players in the industry are getting larger, too, with companies such as BP, Shell, Chevron and Enbridge buying up smaller companies and announcing their own RNG projects.
...

If used for power generation, RNG also can qualify for the Production Tax Credit.

With RNG production, Verbio will have the energy necessary to produce ethanol, make it more efficient and lower the CI score for the ethanol produced at the facility. READ MORE