JANESVILLE, Minnesota – White steam rises into the sky, a rolling cloud visible for miles from the Guardian Energy plant in southern Minnesota.
You can’t see the greenhouse gases being pumped up the chimneys with the water vapor in the air, but they are there – over 178,000 metric tons in 2019 alone. Minnesota corn ethanol is among the top 100 greenhouse gas-emitting facilities in the state, according to a Star Tribune analysis of data from the US EPA’s Greenhouse Gas Reporting Program.
Combined, the state’s corn distilleries produced more than 1.7 million metric tons of climate-toxic gases in 2019. That’s less than 5 percent of Minnesota’s top 100 greenhouse polluters total. But manufacturing what is supposed to be a green alternative to gasoline produces as much pollution as driving 350,000 cars for a year or burning 900,000 tons of coal.
Producers have made progress in reducing the overall carbon intensity of corn ethanol with better crop yields and more efficient distilleries. Minnesota’s total corn ethanol production from 2012 to 2019 increased by 25%; plant greenhouse gases increased by 5% much less, according to EPA data.
“It just keeps getting better,” said Ashwin Raman, spokesperson for the Minnesota Bio-Fuels Association. “It’s something they all take seriously.”
There are differing views on how the carbon footprint of corn ethanol compares to that of gasoline.
The U.S. Department of Agriculture estimates that corn ethanol’s lifecycle greenhouse gases – including what is vented from production facilities – are now about 40% lower than those of ethanol. gasoline. The California regulator estimates it to be 25% to 40% lower, depending on the producer. Other research says it is less.
The latest report, published in the Proceedings of the National Academy of Sciences, concludes that ethanol’s life cycle greenhouse gases are likely 24%. higher than gasoline. Ethanol production and the intensive farming system that accompanies it have had serious environmental consequences, from soil erosion and the destruction of pollinator habitat to the pollution of drinking water wells. and the Mississippi River with nitrates and phosphorus from fertilizer runoff.
“Corn ethanol is not a climate or environmentally friendly fuel,” said the paper’s author, Tyler Lark, a researcher at the University of Wisconsin.
About 200 tractor-trailers a day stop at Guardian’s operation outside of Janesville, a small farming town in the gently rolling fields of Waseca County.
This is the heartland of Minnesota’s ethanol country, and trucks dump loads of corn from surrounding counties into a pit to feed the distillery. Lines of wagons wait to take away ethanol, livestock feed and corn oil for the renewable diesel produced by the plant.
Plant manager Ben Stover said liquid fuels will always have a place in the US economy, even as the electric vehicle revolution progresses.
“I see this as a very important way to achieve significant carbon emission reductions,” said Stover, driving his Ford F150 truck at the factory. “I think we need better technology than lithium batteries.”
In terms of heat units needed to cook a gallon of ethanol, Guardian Energy’s plant is one of the lowest in the industry, Stover said proudly.
The plant’s greenhouse gas emissions rose 6% from 2012 to 2019, according to EPA data, but production grew faster – 32% during that time, the Stover boss said. , Jeanne McCaherty, CEO of Guardian Energy Management, based in Prior Lake. That means greenhouse gases per gallon of ethanol have gone down — progress the industry is trying to build on.
Key to that, McCaherty said, was the new steam-powered heat recovery system he installed about three years ago, reducing his fuel consumption.
“It was a really big deal,” McCaherty said. “We are constantly working on it.”
Other Minnesota ethanol producers echoed those sentiments in interviews, saying their greenhouse gas emissions may have increased, but production had grown faster.
Context matters, McCaherty said. Emissions from all of Minnesota’s ethanol plants combined are still about three times lower than what the Flint Hills oil refinery produces in a year, she noted.
McCaherty chairs the Renewable Fuels Association, a national ethanol trade group whose members are committed to getting their carbon to net zero by 2050. There are a range of strategies, primarily improving fuel efficiency, using more renewable electricity from wind and solar and working with farmers to control emissions by using less fertilizer and other practices.
“There’s not going to be a winning answer to this,” McCaherty said.
Carbon capture and sequestration should play a major role. Across Minnesota, ethanol producers are evaluating two huge proposed carbon dioxide pipelines to cross Minnesota and carry the gas to bury it underground.
Not everyone is on board. Poet, a major ethanol maker, said he was not interested in pipelines: “We’d rather sell our CO2 to Budweiser and Coca-Cola and municipal waste water districts than try to sell it. re-inject into the ground,” spokesman Michael Walz said.
Other strategies are being prepared.
Minnesota lawmakers are again considering a new low-carbon fuel standard like those in California and Oregon. This would require all fuel suppliers in the state to reduce transportation fuel life cycle greenhouse gases by at least 20% by 2035.
Ethanol producers would clearly benefit, but the standard is independent of fuel type, said Brendan Jordan, vice president of the Great Plains Institute, a Minneapolis think tank promoting the approach. The standard would create a powerful incentive to accelerate the decline in ethanol’s carbon intensity, Jordan said.
Fuel suppliers that meet carbon reduction targets can sell carbon credits; those who don’t have them should buy them. The bill, sponsored by Rep. Todd Lippert, DFL-Northfield, and Sen. Dave Senjem, R-Rochester, frames a carbon trading program run by the state Department of Commerce. Last year, a proposed clean fuel standard passed the Democratic-led House in Minnesota, but not the Republican-led Senate.
Such fuel standards, of course, rely on measuring ethanol’s lifecycle greenhouse gas emissions for a carbon intensity score, which has proven difficult. A sticking point is the consideration of greenhouse gases associated with land use change – pushing food production to other lands in order to grow large amounts of corn for ethanol.
Most scientists “grossly underestimate” the emissions associated with this, said Jason Hill, a professor of bioproducts and biosystems engineering at the University of Minnesota.
“Anything associated with the carbon intensity of ethanol is smoke and mirrors,” Hill said. “Anything that increases the amount of corn ethanol we use…will take us in the wrong direction. What ethanol is is another market for corn.”