The biofuels industry is coming down hard on a study it feels has unfairly characterized ethanol from corn stover as being worse for the climate than gasoline and far from qualifying for U.S. EPA's coveted advanced biofuel designation.
Last week, University of Nebraska, Lincoln, researchers published a paper in Nature Climate Change finding that fuels made from corn residue -- the tough, fibrous stalks, corncobs and leaves left atop fields after harvest — could remove carbon from the soil, leading to a net increase of greenhouse gas emissions compared with conventional gasoline over a five-year cycle (ClimateWire, April 21).
Even over 10 years, the fuel didn't come close to meeting the 60 percent greenhouse gas reduction needed to be accepted into the federal renewable fuel standard. The biofuels industry and some government experts were quick to point to alleged flaws in the study, via press releases and blog posts.
"This article makes unrealistic assumptions and uses citations out of context to reinforce the authors' viewpoint," wrote Douglas Karlen, a scientist with the Agricultural Department's Agricultural Research Service in a blog post. Karlen also serves as a consultant for POET-DSM, the developer of a 25-million-gallon-per-year corn stover ethanol plant in Emmetsburg, Iowa, set to open this year.
POET-DSM is asking farmers to harvest only 1 ton of corn residue per acre — about 25 percent of the available material -- according to the company's website. According to Karlen's calculations of the figures in the Nature Climate Change study, the researchers assume a 75 percent collection rate.
According to EPA's analyses and a 2006 study from Argonne National Laboratory, biofuels from corn stover can reduce emissions up to 95 percent compared to fossil fuels. In some cases, they can even surpass 100 percent, a net storage of carbon that can actively help remove CO2 from the atmosphere over time, according to EPA.
"This study lacks sophistication and contradicts without explanation a larger highly regarded, credible body of science," said Bob Dinneen, president and CEO of the Renewable Fuels Association, the ethanol industry's representative in Washington.
To Adam Liska, the lead author of the paper and an assistant professor in the Department of Biological Systems Engineering at the University of Nebraska, the reaction from the paper was expected.
"I have already experienced this backlash for more than two years when I have presented preliminary results to researchers from industry, government, and academia," he wrote in an email. "They are justified in being critical, because my results challenge the prevailing understanding; an understanding which I think is incorrect."
EPA's "folly," said Liska, is assuming that carbon losses from the soil depend on how much corn residue has been removed. They don't, he said.
In his team's simulations, they modeled three residue removal levels: 2, 4 and 6 metric tons per hectare per year, which correspond to about 25 percent, 50 percent, and 75 to 100 percent of annual corn residue production.
"Each of these removal levels produced the same CO2-intensity per unit of biofuel," wrote Liska. "This is a central finding of our research. Which means it is likely that no matter what level of residue is removed, the carbon intensity stays the same."
The cycle of greenhouse gases for these fuels result in a release of carbon dioxide in two ways. They emit CO2 that would have otherwise remained on the ground and decomposed into soil carbon. They also strip the soil of a cover, which leads to the release of existing carbon in the ground. Previous studies, like the Argonne one, do not account for carbon in the corn residue itself.
Flawed and 'highly academic'
Liska's previous work has been cited widely, including by EPA and the renewable fuel standard.
Jeremy Martin, senior scientist in the Clean Vehicles Program at the environmentally minded Union of Concerned Scientists, also thinks Liska's approach is limited. But unlike the biofuel companies and trade groups, he does not think the high removal rates are its biggest flaw. The study doesn't take into account the renewable electricity that is produced as a byproduct of fuel-making, a factor that allows corn residue biofuel to yield such high greenhouse gas savings.
The study also chose a very short time frame — five to 10 years — to measure the life cycle of greenhouse gases from these fuels.
"The paper would have been stronger if it had included a discussion of how the results changed over 30 years or even a century, together with whatever argument the authors have for considering five to ten years the right timeframe to consider," wrote Martin in a blog post on the topic.
For Liska, a 10-year time frame is appropriate.
"Everyone really wants to know how these systems will perform in the first 10 years," he said.
From a financial perspective, the study didn't affect the biofuel markets, said Pavel Molchanov, senior vice president of energy equity research at Raymond James & Associates Inc.
"The headline is not one any biofuel company would want to see," he said, referring to the widespread press the study received. But those holding the money didn't put much stock into it.
"This is a highly academic, somewhat theoretical [study]," said Molchanov.
Representatives from POET-DSM, as well as Abengoa Bioenergy, Quad County Corn Processors and DuPont, will meet at the National Press Club in Washington, D.C., tomorrow to discuss progress on their facilties. Abengoa Bioenergy is expected to begin production at its 25-million-gallon-per-year corn stover ethanol plant in Hugoton, Kan., this year. DuPont will open its 30-million-gallon-per-year refinery in late 2014 in Nevada, Iowa. Quad County Corn Processors is developing a process to turn corn kernel fiber into ethanol.
Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500