Pipeline won’t capture all carbon dioxide emitted by ethanol plants • Nebraska Examiner

The company proposing to build an $8 billion carbon dioxide pipeline through eastern South Dakota says the project will be good for the environment.

The claim is based on the heat-trapping carbon dioxide emitted by ethanol plants, which will be captured, transported by pipeline and stored underground in North Dakota.

“This carbon capture and storage project will have the capacity to prevent the release of 18 million metric tons of CO2 into the atmosphere each year,” the project website states, “or the equivalent of removing the annual CO2 emissions of 4 million vehicles from our roads.”

While that’s true, participating ethanol plants could still emit about 7 million metric tons of additional carbon dioxide per year. That’s because the pipeline would capture only a portion — not all — of the CO2 emitted by the plants.

When ethanol plants process corn into a gasoline additive, they emit two types of CO2: that produced by burning fossil fuels used to power industrial equipment like boilers and grain dryers, and that produced by fermenting the corn.

Summit Carbon Solutions’ pipeline will capture carbon dioxide from corn fermentation. CO2 emitted by gas-powered machinery will be released into the atmosphere.

“There are still emissions associated with corn ethanol that are not being addressed here,” said Daniel Sanchez, an assistant professor in the Department of Environmental Science, Policy and Management at the University of California, Berkeley.

Sanchez said capturing CO2 emissions from industrial equipment, such as boilers and grain dryers, is more expensive than capturing fermentation emissions. Industrial machinery uses a lot of natural gas, which releases more CO2 than it does when burned as fuel. He said that requires additional processes to separate that CO2 from water vapor and other gases.

Iowa-based Summit has partnered with ethanol producers including Poet and Valero to capture CO2 produced by fermentation at 57 ethanol plants in South Dakota and several other states and store it underground in North Dakota. The project, which has not yet received approval from South Dakota regulators, would benefit from federal tax credits that are intended to encourage the prevention of greenhouse gas emissions.

Amount of fermentation emissions unknown

The U.S. Environmental Protection Agency only reports the amount of carbon dioxide emitted by gas-fired ethanol plants. Seven million metric tons is the approximate total emissions from the 57 ethanol plants that Summit partnered with in 2022.

The EPA doesn’t report how much carbon dioxide is emitted during corn fermentation. That’s because fermentation emissions are considered cyclical. Corn pulls carbon dioxide out of the air as it grows in a corn field. It then releases the carbon dioxide back into the atmosphere as it ferments in an ethanol plant. Finally, farmers plant more corn, and the cycle continues.

Summit declined to disclose how much CO2 it emits from fermenting corn at its 57 partner ethanol plants. Ben Nelson, Summit’s director of carbon programs, said a typical 100-million-gallon plant produces about 286,000 metric tons of fermentable CO2.

Berkeley, California-based Sanchez said “modern and efficient” ethanol plants emit about 90,000 metric tons of CO2 during the fermentation process.

The differing estimates mean that Summit’s pipeline and 57 partner plants could capture between 5 million and 16 million metric tons of CO2 from fermentation per year — well within the pipeline’s proposed 18 million metric tons of capacity.

By comparison, in 2022, about 1,300 U.S. power plants emitted about 1.5 billion metric tons of CO2.

“It’s a gigantic pipeline project and a drop in the ocean,” Sanchez said.

Striving for a negative net result

Sanchez added that if an ethanol plant replaces natural gas with a more sustainable solution while also capturing and storing CO2 emissions from fermentation, it could remove more greenhouse gases from the atmosphere than are released during the entire ethanol production cycle at that plant.

Nelson cited a 2022 report for the Renewable Fuels Association that found ethanol production could achieve net negative emissions by 2040. The report found that carbon sequestration at ethanol plants would make the biggest difference — more than industry-wide implementation of agricultural practices that sequester more carbon in the soil, such as less disruptive tillage practices and planting cover crops.

Nelson said the average ethanol plant emits about 55 grams of CO2 for every megajoule (unit of energy) of ethanol produced, and the Summit project will reduce that to about 25 grams of CO2.

“Achieving net negative emissions will also require other efforts, such as climate-smart agriculture, the use of renewable natural gas, renewable electricity in ethanol plants and improving plant efficiency,” Nelson said.

In South Dakota, some ethanol plants already receive so-called “renewable natural gas” from landfill emissions, and a Brookings-area utility is sending methane emitted from dairy manure to be blended with the region’s natural gas supply.

This article was first published in South Dakota SpotlightThe Nebraska Examiner is a sister site to the States Newsroom network.