RFA says two new academic studies show significant GHG reductions from grain-based ethanol

July 17, 2019 |

In Illinois, the Renewable Fuel Association says 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.

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. 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.

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.

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Category: Research

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