Several years ago, Gevo Inc., which operates a biorefinery in Luverne, Minn., approached the University of Minnesota with what seems like an obvious question: How sustainable is the corn it uses in its southwestern facility?
I say “obvious” because almost everyone (experts and nonexperts alike) thinks they already know the answer. It seems like we take it for granted that fuels and chemicals made from corn are a “bad idea” because of corn’s apparently large carbon footprint, which Argonne National Lab estimates to be 371 grams CO2 per kilogram of corn harvested on average in the U.S.
To answer the question, researchers at the U’s Institute on the Environment, supported by an Initiative for Renewable Energy and the Environment grant, asked farmers around the Gevo facility about everything they do up to and including delivery of their grain to the plant gate. We then used this information to calculate the carbon footprint of a kilogram of corn coming from their farms.The average corn farmer, it turns out, is no more real than the average family of 2.5 children. Thirty or so farmers gave us enough detail to assess their carbon footprints. It turns out they are from Lake Wobegon – all “above average” – with carbon footprints far smaller than the U.S. average.
More interesting is how different these individual farms are from each other. The best performing farmers (that is, the lowest carbon footprint farms) deliver corn with less than one-fifth the carbon footprint that the U.S. Environmental Protection Agency and others typically assume for average U.S. corn. The most carbon-intensive farms come in somewhere close to the U.S. average. Indeed, the best farm we found was achieving a net sequestration of carbon in its fields.
Why are they so different? An analysis of our data tells us that farmers at the low end of the scale are doing a few very important things:
- They have integrated animals and animal manure into their production systems, allowing them to avoid fossil energy-intensive fertilizers.
- They are applying conservation tillage practices that help to build up organic carbon in the soil — leading to healthier soils and fields that are carbon sinks instead of carbon sources.
- Many of the farmers who are not using animal manure to reduce their fertilizer use are being much more careful about how much fertilizer they apply. In fact, the farmers with large carbon footprints are using up to twice as much fertilizer as they need to be.
So, what can we learn from all this? For one thing, averages can be misleading — and discouraging. Regulators should be finding ways to encourage farmers to perform like the best farmers, rather than discouraging the best farmers by lumping them all together as average farmers. In a follow-up study released by Colorado State University, researchers have taken a deeper dive into understanding just how much more this cohort of farmers could reduce their carbon footprint by combining the strategies identified in the IonE study.
In the meantime, there are many opportunities for low-carbon biofuels that don’t require massive investments in new technology. We may need those new technologies in the long run, but we can start on the path toward low carbon fuels by simply learning from the best of the best.
John Sheehan was Biofuels Program coordinator at the Institute on the Environment at the time of the study. Currently he is the systems analyst in the Department of Soil and Crop Sciences at Colorado State University.