MADISON, WI – A recent study from the Proceedings of the National Academy of Sciences finds that corn ethanol is a larger contributor to global warming than straight gasoline.
The analysis, published this week in the Proceedings of the National Academy of Sciences, shows that the carbon emissions from using land to grow corn can negate or even reverse any climate advantages of corn ethanol relative to gasoline.
“It basically reaffirms what many suspected, that corn ethanol is not a climate-friendly fuel and we need to accelerate the shift toward better renewable fuels, as well as make improvements in efficiency and electrification,” says lead study author Tyler Lark, a scientist in the Great Lakes Bioenergy Research Center and the Nelson Institute for Environmental Studies at UW–Madison.
In refuting the finding, Scott Richman, chief economist with the Renewable Fuels Association, tells Brownfield Ag News ethanol does not have higher greenhouse gas emissions than fossil fuels. “A lot of other studies come up with something similar in the range of 40 to 50 percent reduction in the carbon intensity for ethanol versus gasoline.”
He continued in noting outside parties like Argon National Lab and California Resources Board have had consistent results when determining environmental impacts of ethanol. “The paper that came out this week is a complete outlier and is a function of the methodology and the way they went about it.”
The research studied the environmental impacts of the Renewable Fuels Standard (RFS) after it was implemented in 2007. The RFS mandates that such fuels partially replace petroleum-based ones. So far, however, the mandate has been nearly entirely fulfilled by corn ethanol.
It found that ethanol is likely at least 24 percent more carbon-intensive than gasoline because of emissions from land use changes to grow corn along with processing and combustion.
“The results confirm what many scientists already realized,” said Lark. “From a climate and environmental standpoint, corn ethanol is not a good biofuel solution. Instead, the findings align with the movement in bioenergy research toward developing next-generation biofuels, such as those made from perennial, non-food plants grown on land less suited for conventional agriculture.
In their studies of changing patterns of land use in the U.S., Lark and his colleague Holly Gibbs, a UW–Madison professor of environmental studies and geography, have noted the expansion of agricultural land dedicated to commodity crops, especially corn. They suspected ethanol production might be playing a role. “We knew it was likely contributing, but we didn’t know to what extent,” Gibbs says.
An analysis platform built on prior modeling studies was used to conduct a more empirical analysis of the connections between policy, ethanol development, land use and environmental outcomes.
“It’s the first time we’ve paired this detailed, rich land use data with the underlying economic drivers,” Gibbs says. “The price data and economic models provided the explanatory power to help us understand the causality behind these changes that we’ve been observing for a decade.”
Enactment of the Renewable Fuel Standard drove up crop prices, their analysis shows, with corn prices rising by 30% and other commodity crops, such as wheat and soybeans, by 20%. From 2008 to 2016, corn cultivation in the U.S. expanded by 8.7%, covering an additional 6.9 million acres of land. This increased agriculture has been accompanied by more fertilizer use (an extra 3–8% each year), more water quality degradation (3–5% increases in nitrate leaching and phosphorus runoff) and more carbon emissions attributable to land use changes.
“Those effects impact everyday life for people across the country,” says Lark. “Nitrogen and phosphorus runoff contribute to harmful algal blooms and dead zones in lakes, rivers and the Gulf of Mexico. And nitrate leaching can contaminate groundwater and drinking water; it’s not uncommon for municipalities in Midwestern states to have to build new water treatment plants to treat nitrate in their water from agricultural pollution. Corn ethanol is worsening these problems.”
“This one policy effectively bumped up pollution from the entire agricultural industry by several percent,” Lark says.
The sum effect is that the carbon emissions of corn-based ethanol produced to meet the Renewable Fuel Standard are at least as high as those from the equivalent amount of gasoline and possibly higher — likely by 24% or more.
“The EPA’s original estimates suggested that U.S. land use change would sequester carbon and help improve the carbon footprint of ethanol. But in retrospect, we now know it did just the opposite,” Lark says. “Rather than reduce the carbon intensity of ethanol to 20% lower than gasoline, it looks like it actually increases it to that much higher than gasoline.”
The results are especially timely, he says, because the Renewable Fuel Standard mandates specific annual biofuel volumes through 2022; once these requirements expire, the Environmental Protection Agency will take over the role of determining how much and which types of biofuel should be produced each year to meet the standard. What comes next policy-wise could have a very large effect on climate change, Lark says. “It’s a pivotal moment for deciding what this policy — and our landscape — should look like moving forward.”
