A paper authored by UNL assistant professor Adam Liska, the lead researcher, was published Sunday in the journal Nature Climate Change, UNL said in a statement.
The study’s findings, the university said, “cast doubt on whether corn residue can be used to meet federal mandates to ramp up ethanol production and reduce greenhouse gas emissions.”
The ethanol industry disputes the paper’s findings, said Todd Sneller, administrator of the Nebraska Ethanol Board. Other highly credentialed researchers, Sneller said, are submitting an academic research paper with opposite conclusions. Because that paper is in the publication review process, Sneller declined to identify the authors.
The debate is over material known as corn stover — the stalks, leaves and cobs found in fields after harvest — that has been considered a ready resource for making ethanol, or motor fuel from organic sources such as corn, sugar cane or waste products. Nebraska is the second-largest ethanol producer in the country, Iowa the first. And both have a lot of corn leftovers, as Iowa is the largest corn producer and Nebraska the third.
Using what the industry calls “biomass” to create a motor fuel known as cellulosic ethanol has been an endeavor long in the works. It has not reached commercial success. But efforts continue, with about $1 billion of capital investment in cellulosic plants being built in Iowa and Kansas.
About $50 million was spent on a test plant in York, Neb., part of the biofuel company Abengoa, which plans to take the technology live this year or next at a commercial refinery in southwest Kansas.
The UNL research, funded by the U.S. Department of Energy, used a supercomputer to estimate the effect of corn leftover removal on 128 million acres across 12 Corn Belt states. The team found that removing crop residue from cornfields as opposed to leaving it as is generates an additional 50 grams to 70 grams of carbon dioxide per megajoule of biofuel energy produced.
The UNL research found that total annual production emissions from turning the biomass into ethanol, averaged over five years, would equal about 100 grams of carbon dioxide per megajoule, a unit of energy equal to that possessed of a one-ton truck traveling at 100 mph.
Those production emissions are 7 percent greater than gasoline emissions and 62 grams above the 60 percent reduction in greenhouse gas emissions required by the 2007 Energy Independence and Security Act, UNL said.
“If this research is accurate, and nearly all evidence suggests so, then it should be known sooner rather than later, as it will be shown by others to be true regardless,” lead researcher Liska said in a statement.
The study’s findings, UNL said “likely will not surprise farmers, who have long recognized the importance of retaining crop residue on their fields to protect against erosion and preserve soil quality.”
The three cellulosic ethanol plants under development in the Midlands are the Abengoa plant in Kansas, a DuPont refinery in Des Moines and one by South Dakota-based bio-refiner POET in Emmetsburg, Iowa.
Doug Karlen, a USDA soil scientist in Ames, Iowa, who is a technical consultant for POET on the Emmetsburg plant, said the UNL research based its conclusions on unrealistic stover harvest assumptions. He said the paper contemplates a 75 percent stover harvest from corn fields, which Karlen called unrealistic and impractical.
“First, you would have stover stacked to high heaven,” Karlen said. “’Excessive removal’ are the key missing words from the research paper.”
Jan Koninckx, global business director for biorefineries at DuPont, also disputed the findings.
“The core analysis depicts an extreme scenario that no responsible farmer or business would ever employ because it would ruin both the land and the long-term supply of feedstock,” Koninckx said.
Koninckx said an analysis of DuPont’s 2013 corn-stover harvest using USDA soil models indicated soil carbon was stable or increasing on the “overwhelming majority” of the acres tested.