“We think it’s a big opportunity to improve the carbon intensity of existing biofuels, help meet the low-carbon fuel standard, reduce emissions [and] start building out CCS pipelines all across the United States,” said Daniel Sanchez, a researcher at the Carnegie Institution for Science who led the research published in the Proceedings of the National Academy of Sciences.
The fermentation process in which ethanol is created generates a nearly pure stream of carbon dioxide, and right now, for the most part, it ends up in the atmosphere. The United States’ 216 ethanol refineries emit 45 million tons of the global-warming gas each year in this manner, reports the study, which was co-authored by scientists from institutions in the United States and Austria.
But one installation, Archer Daniels Midland’s Decatur Plant in Illinois, is now burying some of that carbon dioxide instead, amounting to an expected 1 million tons or more per year. Other plants could follow, attracted by the relative simplicity of separating carbon dioxide from the ethanol-making process and incentivized by legislation that just passed Congress that gives a $50-per-ton tax credit for storing large volumes of carbon deep underground.
Sanchez says applying CCS to ethanol could be the bridge that finally leads to the development of a major bioenergy and carbon capture and storage (BECCS) industry — one that is well behind schedule, if you ask the scientists who think we will need it to pull billions of tons carbon dioxide out of the atmosphere annually later in this century.
But ethanol critics — who charge that the industry is driving up food prices, indirectly causing the clearing of additional land and more — seem unlikely to be placated by the burying of carbon.
Ethanol is a bad choice to begin with, and capturing carbon would only mitigate that, argued Tim Searchinger, a researcher at the World Resources Institute and Princeton University, in response to the new study.
“If you are going to produce ethanol, then it would be good to apply CCS, just as if you are going to burn coal, it is good to apply CCS,” Searchinger wrote in an email. “The danger is using this prospect of CCS to increase either. My concern with this article is that its discussion, without going into these issues, claims that doing so is not just less bad but good.”
Indeed, as the industry has grown in the past decade, supported by friendly government policies that require the blending of ethanol into gasoline, an epic environmental battle has ensued.
Ethanol proponents often say the fuel is “carbon neutral” because, while carbon dioxide is released when ethanol is burned (just as with gasoline), the corn plants the ethanol came from pulled an equal amount of carbon dioxide from the atmosphere as they grew. “Ethanol and other biofuels are simply recycling atmospheric carbon,” argues the Renewable Fuels Association, the ethanol industry’s trade organization.
But critics say that is too simplistic. There are other energy costs in the process of making ethanol, and there are additional environmental consequences of growing more corn, such as the transformation of prairie landscapes and large inputs of fertilizer that can eventually contribute to algal blooms.
Moreover, these critics say, the industry would have to go beyond simply burning plants and set aside additional land that stores carbon to create a greenhouse gas benefit. Instead, it’s been charged with having the opposite effect — incentivizing farmers around the world to convert more land to cropland, thus causing even more carbon dioxide to go into the atmosphere.
Into this mix comes the new study, which says that for a cost of less than $25 per ton, ethanol refineries could prep 27 million of the 45 million tons of carbon dioxide they emit to instead be transported by pipeline. There are costs for geological injection of the CO2 and for its transportation, but with the $50-per-ton tax credit, and even more favorable paybacks from California, it could be worth it.
Indeed, the study’s economic model finds that with a hypothetical tax credit of $60, the industry would probably develop an entire new pipeline network just to transport carbon dioxide. By sequestering carbon, the carbon intensity of ethanol could drop by 40 percent, it concludes — making the fuel more competitive against gasoline from an environmental standpoint.
“I think it’s a pretty positive story and one that comes from a pretty strained marriage of something I think a lot of environmental groups might not like separately, which is corn ethanol and carbon capture,” Sanchez said.
But Searchinger says Sanchez is relying in part on an analysis that assumes the carbon neutrality of biofuels, rendering it problematic.
“The assumption of carbon neutrality is so fundamentally incorporated into the literature and other analyses that people using them don’t even realize it,” he said.
Sanchez, however, says that he does not think ethanol is carbon neutral and that sequestering carbon from the process would not go so far as to make it carbon negative — in other words, it wouldn’t lead to a net subtraction of carbon from the air.
But it would take some carbon away, and if the same process were someday applied to more advanced biofuels like cellulosic ethanol, true “negative emissions” might be possible, he said.
“If I had to bet, I’d say the ethanol industry is the first industry in the U.S. to capture half of its emissions,” Sanchez said.