redOrbit Staff & Wire Reports – Your Universe Online
Research published Sunday in the journal Nature Climate Change is calling into question whether or not corn crop residue can be used to meet US government mandates to increase the production of biofuels and reduce greenhouse gas emissions.
In fact, University of Nebraska-Lincoln Department of Agronomy & Horticulture assistant professor Adam Liska and his colleagues report that using corn residue to create ethanol or other types of biofuel actually reduces soil carbon and could generate more greenhouse gases than gasoline.
According to the researchers, the stalks, leaves and cobs left in cornfields following a harvest has been viewed as a good resource for the production of cellulosic ethanol. The US Department of Energy has invested more than $1 billion in federal funds in order to support research to develop ethanol made from this matter (which is also known as corn stover), though the process has not been extensively commercialized as of yet.
However, using a supercomputer model developed at the university’s Holland Computing Center, Liska’s team estimated the impact of residue removal on 128 million acres dispersed across 12 different states in the Corn Belt. They discovered that removing crop residue from these cornfields would cause the creation of an extra 50 to 70 grams of carbon dioxide per megajoule of biofuel energy produced.
The total annual emissions, averaged over a period of five years, would be approximately 100 grams of CO2 per megajoule, which would be seven percent higher than gasoline emissions, the study authors explained. That would also be 62 grams higher than the 60 percent greenhouse gas emission reductions required by the 2007 Energy Independence and Security Act.
Furthermore, Liska and his associates report that the carbon emission rate remained constant, no matter how much stover was removed. If less residue is removed, there is less decline in soil carbon, but it also results in a lower biofuel energy yield, the professor noted.
“To mitigate increased carbon dioxide emissions and reduced soil carbon, the study suggests planting cover crops to fix more carbon in the soil,” the university said in a statement. “Cellulosic ethanol producers also could turn to alternative feedstocks, such as perennial grasses or wood residue, or export electricity from biofuel production facilities to offset emissions from coal-fueled power plants.”
Liska said that his team attempted to find flaws in the study, but were unable to do so. “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,” he added. “Many others have come close recently to accurately quantifying this emission.”
The study was funded through a three-year grant from the Energy Department valued at $500,000, and used carbon dioxide measurements taken between 2001 and 2010 in order to validate a soil carbon model developed using information from three dozen international field studies.
The researchers used USDA soil maps and crop yields to extrapolate potential CO2 emissions across 580 million 30 meter by 30 meter regions in the Corn Belt states referred to as “geospatial cells.” Their findings indicate that the highest net loss of carbon from residue removal occurred in the states of Minnesota, Iowa and Wisconsin, due to cooler temperatures and an increased amount of carbon in the soil.