Fall 2022

Natural Selections

Cows laying and grazing in a field.
Photo by Michael P. King


Reducing greenhouse gas emissions is a critical step in mitigating climate change. One way to do this is to expand renewable fuels, which can also decrease reliance on imported oil. That was the intent of the U.S. Renewable Fuel Standard (RFS) Program, created by Congress in 2005. But a recent study of the program’s impact shows it may have backfired, and additional policy changes are needed to get it back on track.

The study was conducted by researchers at UW–Madison and several other universities, including faculty and staff from CALS and Grassland 2.0 — a diverse group of scientists, farmers, and professionals that studies and facilitates conversation around grassland-based agriculture. The team found that the greenhouse gases stemming from corn ethanol actually negate any of its advantages over gasoline. Why? The RFS policymakers did not predict the full-scale impacts of the land-use change that would result from its implementation — mainly more corn and less carbon-storing grassland.

“Any time you drive up demand for commodity crops like corn and soybeans, you’re going to stimulate more of those crops on our landscapes,” says study coauthor Tyler Lark, a lead scientist at UW’s Center for Sustainability and the Global Environment and Grassland 2.0 collaborator. “Alternatively, policies that support grassland-based agriculture could help sustain our rural economies while also enhancing carbon sequestration, water quality, and wildlife habitat.”

“…The conversion of grassland to cropland spurred by the [U.S. Renewable Fuel Standard Program] led to more soil carbon loss…”

Eric Booth

The research team used data-driven analyses and explanatory modeling based on actual observations of changes in crop prices and land use. They found that, during the first eight years of the policy’s implementation (2008 to 2016), the RFS led to a 31% increase in corn prices. This increase spilled over to other crops, driving a 19% increase in soybean prices and a 20% increase in wheat prices. The result? Incentives arose to plant more corn, grow more continuous corn, and devote more land to crops. The RFS incentivized corn and disincentivized grasslands, such as pasture and land enrolled in the federal Conservation Reserve Program, which pays farmers to maintain environmentally sensitive agricultural lands as perennial vegetation.

The increase in corn production correlated with a 3–8% increase in annual fertilizer use, which, in turn, increased water pollutants by 3–5%. Studies show that the transition to more corn and less grassland also means less carbon storage on the landscape. And research from Grassland 2.0 demonstrates that grassland and well-managed pasture store more carbon than annual row crops, thereby helping to mitigate climate change.

“One of the main arguments for the RFS at its inception was its potential to reduce greenhouse gas emissions,” notes Eric Booth, a scientist in the Department of Agronomy. Booth is a coauthor on the paper and a member of Grassland 2.0’s grassland modeling team. “Unfortunately, as some initial critics suspected, the conversion of grassland to cropland spurred by the RFS led to more soil carbon loss; and additional corn acres, which require high levels of nitrogen fertilizer, released even more greenhouse gases. On top of that, land converted to crops, which tended to be more marginal, is much more susceptible to erosion and nutrient loss. Our models, grounded in real-world observations, were able to capture these important processes.”

The Grassland 2.0 study adds to the discussion on the types of public policy needed to support the nation’s food, energy, and water needs. The research team contends that the study also provides critical evidence that policies incentivizing perennial grassland such as well-managed pasture can be a critical step to reducing greenhouse gases while meeting those needs.

The Environmental Protection Agency is scheduled to release proposed RFS requirements in November 2022; the CALS and Grassland 2.0 team published their results just in time for them to be part of the discussion. As Lark notes, “Decisions made this year have the potential to impact our climate and landscape for decades to come.”

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