GREET Model is Key for Science-Based Climate Policy

Lindsay Croke

May 07, 2024  |  Ethanol

If America’s goal is truly to decarbonize the transportation sector, the rules by which we determine which practices and products will accomplish the goal must be based on sound science.


On April 30, the U.S. Department of Treasury released guidance on the Sustainable Aviation Fuel (SAF) tax credit, established by the Inflation Reduction Act (IRA). Among other details, the guidance established how fuel's carbon intensity would be measured to achieve the 50 percent reduction in greenhouse gas emissions required by the IRA.


According to the guidance, fuel producers who meet the GHG reduction requirement are eligible for a $1.25 per gallon tax credit. SAF can receive up to $1.75 per gallon tax credit for GHG reductions over the required 50 percent.


The devil is in the details as they say because measuring the GHG emissions of various fuels can be difficult to do. The pursuit is for the most scientifically sound model that will accurately account for GHG emissions with little to no political bias. Enter the GREET model.


GREET stands for Greenhouse gases, Regulated Emissions, and Energy use in Technologies. It was created in 1995 by Argonne National Laboratory at the request of the U.S. Department of Energy as a tool to evaluate the lifecycle analysis of technologies or products. GREET is important in calculating the carbon scores of the transportation industry.


Agriculture believes GREET to be the most scientifically based model because the model continually incorporates updated information. To grow more with less, agriculture utilizes innovations in seed genetics, animal genetics, fertilizers, cropping systems, and animal nutrition. These have powered agriculture to improve at a significant rate – an improvement that is not accounted for in other GHG models.


As an example, in the early 2000s, 1 bushel of corn would produce 2.7 gallons of ethanol. Today, one bushel of corn produces 3 gallons of ethanol, an 11 percent increase. Since 2000, water consumption per gallon of ethanol has been reduced by over 53 percent. And the average corn yield per acre has increased from 137 bushels in 2000 to 206 bushels in 2023. A model that does not take notice of these drastic improvements does not fully capitalize on the carbon reduction that agriculture has to offer.


Of course, there are other models, like the CORSIA (Carbon Offsetting and Reduction Scheme for International Aviation) model from the International Civil Aviation Organization. Agriculture can prove that the data backing up this model is outdated and thus, no longer scientifically reliable. The latest GREET model uses 2022-era crop and fuel production data while CORSIA relies on two sets of agricultural data ranging in age from 2006 to 2012. To achieve the maximum GHG emissions reduction that our planet needs, our policies must be built on the most current and reliable data.

The U.S. Department of Treasury selected the GREET model for the basis of the U.S. tax credits related to SAF through the end of 2024. That’s a homerun in our book, even if there were other details about the announcement that Illinois agriculture believes still needs work. The good news is that new guidance released later this year will impact the tax credit in 2025 through 2027. Using the GREET model, we can fix what Treasury missed as we help them understand farming, farming practices, and how each soil type and region of the country farms differently.