Here in the US, we’ve gotten quite acclimated to the idea that, unless we’re filling our cars with rec gas, we’re getting up to 10% ethanol with our gasoline. Specifically, we’re talking about corn ethanol – an alcohol produced from particularly high-starch strains of corn, whose use as an octane-boosting fuel additive actually stretches all the way back to around the 1920s, but which didn’t really see its time in the limelight until the 2000s with the introduction of E85. We’ve been led to believe that it’s an environmentally friendly sort of fuel additive, as corn pulls carbon dioxide out of the atmosphere before it’s distilled and burned, helping offset the CO2 it releases.
Yeah, it turns out we might have gotten that one a bit wrong.
A new study out of the University of Wisconsin-Madison suggests that corn ethanol could actually be worse on the whole – environmentally speaking – than straight gasoline. The study was published in the Proceedings of the National Academy of Sciences, and it estimates that corn ethanol is fully 24% more carbon-intensive than gasoline at least, mostly due to the change in land use resulting from its widespread adoption.
Basically, what it boils down to is this: soil traps carbon, and when a plot of land is cleared for agricultural use and tilled, much of that trapped carbon is released into the atmosphere. The 2005 Renewable Fuel Standard law called for some 15-billion gallons of corn-derived ethanol to be mixed into the nation’s gasoline supply every year, and as a result, 6.9 million additional acres of land were converted for corn farming between 2008 and 2016. That’s a lot of trapped carbon being released.
Granted, the carbon release from soil tilling is a one-time emission event; over a long stretch of time, corn ethanol is ultimately less emitting than gasoline, and there’s a theoretical break-even point where the emissions reductions from the ethanol itself equals the emissions from that single tilling event. But the University of Wisconsin-Madison study considered a 30-year timeline, which is a plenty long timeline if we believe that the day of the battery electric vehicle and the hydrogen-powered automobile is truly right around the corner.
“Corn ethanol is not a climate-friendly fuel,” says the study’s lead author, Dr. Tyler Lark.
The study’s findings are somewhat at odds with the EPA’s 2010 study on alternative fuels, which put the emissions break-even point for E85 ethanol at 14 years. It’s even more at odds with a 2019 study by the USDA, which suggested that corn ethanol was a full 39% less carbon-intensive than gasoline. Dr. Lark’s response: those studies failed to account for the magnitude of the land conversion problem.
So what are the alternatives? Well, as Jason Fenske of Engineering Explained covers in his recent video about the study (above), switchgrass is another potential source of ethanol, and one that’s substantially more emissions-friendly than corn. In fact, according to the data, using switchgrass as an ethanol source would have a break-even point of zero years, and would achieve a staggering 60% reduction in carbon emissions within three years.
Or, we could hold out hope for cutting-edge efforts to generate ethanol out of thin air. Two startups, Twelve and LanzaTech, are teaming up in the hopes of doing just that. Basically, Twelve’s carbon transformation technology pulls CO2 out of the atmosphere and converts it to CO, which LanzaTech’s Continuous Stirred Tank Reactor then transforms into ethanol. It’s all very scalable, in theory, and it could be used to generate ethanol at an industrial scale without the need for any plant mass.