Two new academic studies released this week provide further evidence that grain-based ethanol is significantly reducing greenhouse gas emissions and call into question the reliability of recent “land use change” analyses based on flawed satellite imagery-based methodologies.
These studies add to a large body of existing literature that debunks falsities spread by well-funded opponents about the role ethanol plays in protecting the environment.
According to the Renewable Fuels Association, this new research will allow policymakers and regulators to focus on the fact that corn farmers and ethanol producers alike are making great strides forward in sustainability and efficiency.
“As the Environmental Protection Agency considers the GHG impacts of expanded ethanol consumption under the Renewable Fuel Standard, we urge them to strongly consider the latest science and data regarding ethanol’s tremendous carbon benefits,” said RFA President and CEO Geoff Cooper. “At the same time, we implore EPA to exercise great caution and prudence when considering the results of flawed land use change studies reliant on data from satellites that, frankly, can’t tell the difference between a pasture and a parking lot. The land use research relied upon by EPA for its Second Triennial Report to Congress was so flawed and erroneous that it simply cannot be used for regulatory decision-making, and we urge EPA not to make the same mistake as it considers future regulatory actions on the RFS.”
The first new study, conducted by the Laboratory for Applied Spatial Analysis at Southern Illinois University Edwardsville (SIUE-LASA), exposes fundamental flaws in satellite imagery-based research regarding land use change that was quoted in the EPA’s Second Triennial Report, released in 2018. SIUE-LASA’s review of the data sets and methodologies that were used in the prior research revealed some remarkable errors.
A series of papers by Tyler Lark, Holly Gibbs and Christopher Wright relied heavily on use of the U.S. Department of Agriculture’s Cropland Data Layer (CDL), which assigns land type categories using satellite imagery. Their research suggests there has been conversion of grassland and other “native” lands to cropland since the Renewable Fuel Standard was established. However, the CDL has shortcomings that render it poorly suited for this type of analysis, notably the inability to differentiate between grassland types (native prairie, Conservation Reserve Program, grass hay, grass pasture and fallow/idle grasslands), a problem USDA itself has recognized.
In one egregious example where the CDL failed, a body of water was misclassified as deciduous forest and grass pasture. Click here for the image example. This example is symptomatic of the errors associated with the CDL, underscoring why the research based on this data should not be used for regulatory decision-making.
Additionally, the research by Lark, Gibbs, and Wright (much of which was funded by the National Wildlife Federation) is prone to reflecting “false change,” in which a higher share of actual cropland is recognized in the newer, more-accurate CDL versions than in older, less-accurate versions, thus giving the appearance that cropland expanded.
For example, SIUE-LASA examined conditions in Iowa, since it is a leading producer of corn and ethanol and previous research asserted Iowa was an area with significant land use change. Using data from the USDA’s National Agricultural Statistics Service, SIUE showed that from 2008 to 2012 in Iowa there was a net increase of only 38,000 acres of cropland as opposed to 263,468 acres and 295,100 acres claimed in two satellite data-driven papers cited by the EPA in its 2018 report.
The land use research (“Critical Review of Supporting Literature on Land Use Change in the EPA’s Second Triennial Report to Congress”) was conducted for Renewable Fuels Association by Joshua Pritsolas and Dr. Randall Pearson of SIUE-LASA. In summary, the authors found “…there are major concerns regarding both the data and the methods that were used by the researchers [Lark, Gibbs, Wright], which call their findings into question.”
The second new study, a worldwide meta-analysis funded in part by the Department of Energy and USDA, determined that corn residue (“stover”) retained on fields—which is the common practice—results in the sequestration of approximately 0.41 metric ton of carbon per hectare per year in the soil. This implies not only that the carbon intensity of corn-based ethanol is significantly below current estimates by EPA, the California Air Resources Board, and others, but also that leaving more residue on the field can have a larger carbon benefit than significant removal and conversion of the residue into ethanol.
Based on this research, properly accounting for the soil carbon sequestration benefits of corn production would reduce the existing lifecycle “carbon intensity score” of corn ethanol by some 20-25 percent, meaning most dry mill corn ethanol produced today would result in a 50-65 percent GHG savings compared to gasoline.
The soil carbon sequestration research was conducted by a team of environmental and soil scientists from the Department of Energy’s Argonne National Laboratory, the U.S. Department of Agriculture’s Agricultural Research Service, South Dakota State University and the South Dakota School of Mines and Technology. They used 409 data points from 74 stover harvest experiments conducted around the world. The paper, titled “A global meta-analysis of soil organic carbon response to corn stover removal,” was recently published in GCB Bioenergy, an international journal. Click here to read it.