Modern human energy consumption can be compared to Sesame Street’s Cookie Monster. Just like Cookie Monster is always hungry for cookies, humans are always hungry for energy. Since Cookie Monster eats more and more cookies everyday, eventually, all the cookies will be gone. Likewise, as nonrenewable energy sources are quickly being depleted in nearly every corner of the world, scientists across the globe have been hunting for new materials and methods to generate clean and sustainable energy from renewable resources.
One popular source of clean energy biofuels is corn. However, a research team from the University of Nebraska – Lincoln found that using corn stover to make ethanol and other biofuels reduces soil carbon and can actually generate more greenhouse gases than gasoline. Their study was published two weeks ago in the journal Nature Climate Change. In their article, the team of researchers, led by assistant professor Adam Liska, cast doubt on whether or not corn residue can be used to meet federal mandates of increasing ethanol production and reducing greenhouse gas emissions.
Corn stover, which consists of the stalks, leaves, and cobs left in cornfields after a harvest, is considered a ready resource for cellulosic ethanol production. The U.S. Department of Energy has provided over $1 billion in federal funds to support research to develop cellulosic biofuels, such as ethanol made from corn stover. While the cellulosic biofuel production process is not yet extensively commercialized, several private companies are developing specialized biorefineries that are capable of transforming hardy corn fibers into usable fuel.
In order to perform their experiment, the research team used a supercomputer model at the University of Nebraska – Lincoln’s Holland Computing Center to visualize and estimate the effects of corn stover removal on 128 million acres of farmland across 12 Corn Belt states. Until now, scientists have been unable to thoroughly quantify exactly how much soil carbon is lost to carbon dioxide emissions after removing the crop residue. They have been hindered by limited carbon dioxide measurements in cornfields, by the fact that annual carbon losses are comparatively small and difficult to measure, and the lack of a proven model to estimate carbon dioxide emissions that could be coupled with a geospatial analysis.
The study was funded through a grant from the U.S. Department of Energy. Liska and his team of researchers used carbon dioxide measurements taken from 2001 to 2010 to validate a soil carbon model that was built using data from 36 field studies across North America, Europe, Africa and Asia. Using USDA soil maps and crop yields, the researchers extrapolated potential carbon dioxide emissions across the Corn Belt states. The USDA soil maps showed that the states of Minnesota, Iowa and Wisconsin had the highest net loss of carbon from residue removal because they have cooler temperatures and more carbon in the soil.
The researchers found that after residue removal, total annual production emissions, averaged over five years, is 7% greater than gasoline emissions. Additionally, the research team discovered that total annual emissions after removing residue was 62 grams above the average 60% reduction in greenhouse gas emissions that are required by the 2007 Energy Independence and Security Act. Most importantly, the researchers found that the rate of carbon emissions is constant regardless of whether a small amount of corn stover is removed or nearly all of it is stripped away.
In their study, the researchers suggested several methods to alleviate increased carbon dioxide emissions and reduced soil carbon. One suggested options is planting cover crops to fix more carbon in the soil. Another option is for cellulosic ethanol producers to turn to alternative feedstocks, such as perennial grasses or wood residues. The researchers also presented the option of exporting electricity from biofuel production facilities to balance out emissions from coal-fueled power plants. The fourth option the researchers proposed was to develop more fuel-efficient automobiles, thereby significantly reducing the nation’s demand for fuel.
Interestingly enough, the findings of the researchers’ study most likely will not surprise farmers, as farmers have long recognized the importance of retaining crop residue on their fields to protect against erosion and to preserve soil quality.
Please note All comments are eligible for publication in The News-Letter.