Federal renewable fuel mandates have created an industry around corn ethanol that now consumes nearly a third of the U.S. corn crop. But what is the rationale behind those mandates in the first place? Several scientists have asked and found the answers to be unsound.
When the Environmental Protection Agency revised its renewable fuel standards in February, the agency recalculated the lifecycle emissions of corn ethanol to find that it was 20 percent less greenhouse-gas emitting than gasoline and, therefore, qualified as a renewable fuel. Some wondered what had changed since an EPA review issued less than a year before found that emissions from corn ethanol were too high for it to qualify.
As it turns out, none of the actual data about emissions from biofuels changed — just the way the EPA presented it.
Specifically, the agency’s new fuel standards assess each biofuel based on its assumed greenhouse gas emissions in the year 2022, the deadline by which renewable fuel production must be at levels mandated by the Energy Security and Independence Act of 2007.
But focusing on the amount biofuels are expected to emit in 2022 “distorts the picture of today’s biofuels,” according to Jeremy Martin, a senior analyst in the Union of Concerned Scientists’ Clean Vehicles Program. Lifecycle emissions from corn ethanol, for instance, are only expected to decline in 2022 because of expected increases in the yields of corn crops and improvements in biorefining technology by that year.
Even the EPA’s own analysis “shows that, in the near term, natural-gas-powered, dry-milled corn ethanol production results in an increase of greenhouse gas emissions of 12 to 33 percent compared to gasoline,” says Joe Fargione, a lead scientist at the Nature Conservancy. Those numbers can be found in spreadsheets that the agency posted to its own Web site.
In March, the American Petroleum Institute and the National Petrochemical & Refiners Association sued the EPA over the new standards. The two groups argue that by publishing the standards after an original deadline, the EPA has left oil companies with obligations to buy and supply biofuels that will raise gasoline prices unfairly if oil companies are forced to meet those obligations on time.
A lawsuit against the EPA also seems warranted, though for different reasons, to Richard Plevin, a Ph.D. candidate in the Energy and Resources Group at the University of California, Berkeley, who studies the lifecycle emissions of biofuels.
“I think it’s completely reasonable for environmental groups to sue the EPA based on its own analysis and say, ‘These fuels don’t meet the requirements of the program,’” Plevin argues.
Plevin recently spoke about the issue before a National Research Council committee which is reviewing projections of future U.S. biofuel production and its impacts, including the EPA’s own new renewable fuel standards.
According to the agency’s final review of the standards, 2022 emissions were the focus because, in part, it would be too difficult to “track how biofuel production might continuously change from month to month or year to year.” But the EPA already has published estimates of emissions from most biofuels in 2012 and 2017 — the increase that Fargione described, for instance, is projected to occur in 2012. So why were the 2022 numbers the only ones used in the final review?
“Clearly, there was support for continuing the conventional biofuel program: that’s the instruction the EPA got,” says Martin. “So I wouldn’t call that a problem with their analysis. They were just doing what they were ordered to do by law.”
Best Models Aren’t Precise Enough
The EPA used the best existing scientific and economic models to predict future greenhouse gas emissions, say Fargione and Plevin. The problem is that even those models are unable to give precise estimates for how much will be emitted from various sources 12 years from now.
Lifecycle analysis is an attempt to measure every way in which the increased production of a biofuel affects the total amount of greenhouse gas emitted. But these effects are difficult enough to measure now, let alone predict for the future.
When a forest is razed to make way for a new field of a biofuel crop, for instance, a huge amount of carbon is released from the organic matter that used to keep carbon sequestered in the forest. This is known as an “indirect land use change”.
Other examples abound. Fertilizers used on corn result in the emission of nitrous oxide, which is the biggest single contributor to greenhouse gas emissions from corn ethanol, according to Plevin. And increased demand for corn has caused farmers to abandon rotation methods in favor of planting corn in the same field year after year. That method requires yet more fertilizer, and also lowers crop yields, which causes even more land to be converted to cornfields, according to a paper Fargione co-authored.
“More progress is urgently needed across a range of feedstocks to improve the sustainability of biofuel production,” says Fargione.
In some ways, though, biofuel production appears to mitigate greenhouse gas emissions. Where biofuel crops outcompete rice crops or livestock farms, according to Plevin, they cause methane emissions to drop, because both types of agriculture are major sources of methane.
But this scenario would result in considerably lower food production, Plevin says, which would in turn trigger new greenhouse gas emission. When he and some researchers from Purdue University held food consumption constant and modeled a situation in which biofuel crops outcompete rice and livestock, indirect land use change increased by 40 percent to keep the level of food production steady.
“It’s an inexact assessment, but there are emissions associated with reductions in food,” Plevin says.
EPA Counting on Increasing Yields
Finally, the EPA’s rosy outlook for 2022 relies heavily on the assumption that crop yields will increase by that year, due to improvements in farming and refining technology. Plevin isn’t so sure — in part, because the effects of climate change on agricultural yield are still somewhat uncertain. One recent study by the International Food Policy Research Institute, for example, indicates that by 2050, irrigated corn crops in developed countries will yield between 1 and 9 percent less than they did in 2000.
“At the very least, we have to say that there’s uncertainty in those projections into the future, and that the further out we go there’s more doubt that the numbers we’re using are the right numbers,” according to Plevin.
The EPA used several economic models to estimate crop yields in 2022, one of which came from the Food and Policy Research Institute (FAPRI) at Iowa State University. Bruce Babcock, professor of economics and director of the university’s Center for Agricultural and Rural Development, which hosts FAPRI, says it’s “impossible” to predict exact future yields, even with the FAPRI model.
Babcock thinks the models should be used to inform decisions, and that the EPA chose the best models for estimating future emissions. But he agrees with Plevin, Martin and Fargione that those estimates are not yet sound enough to warrant mandates regulating the production of biofuels.
“My opinion is that the models are not reliable to stand up in a court of law, and I use that standard because regulations have the force of law,” Babcock says.
Martin, Fargione and Plevin think more effort should be invested in researching and developing unconventional biofuels, such as cellulosic fuels, frequently made from grasses and scrub trees. The EPA’s first renewable fuel standards required cellulosic biofuel production to reach 100 million ethanol-equivalent gallons in 2010, but the new standards reduced that to a paltry 6.5 million gallons, indicating how poorly the cellulosic biofuel industry is doing.
“The overall goals of EISA and the course the nation has set for getting to lower-carbon biofuels really depend on the successful commercialization of cellulosic biofuels,” says Martin. “Even to achieve the corn numbers [the EPA] is showing in 2022, we need to make the transition away from relying on current biofuels.”
Ultimately, Plevin says, the government shouldn’t be asking itself “how to regulate within a given mandate, but ‘Should we have a mandate at all?’”
“I think it’s reasonable to think about the biofuels which you can say, on principle, are much lower-risk,” he says, such as cellulosic fuels and fuel from algae, which don’t require land use changes.
“Let’s put our money into those. Or wait until 2022, when you know the yields, and the risk is reduced.”
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(Photos, top to bottom: bravesirrobin/CC BY 2.0; spencerthomas/CC BY 2.0)