On Nov. 24, the Renewable Fuels Association hosted a press conference featuring several experts in the field of biofuel life cycle greenhouse gas (GHG) analysis and agricultural land use. The speakers addressed the flawed arguments made by ethanol opponents during a media call hosted earlier in the day by the American Petroleum Institute.

Geoff Cooper, senior vice president of the RFA, opened the call noting that the API’s call featured convoluted arguments aimed at undermining the globally accepted carbon accounting methodologies for bioenergy. He noted researchers Timothy Searchinger and John DeCicco continue to claim GHG emissions from biomass and biofuels are no different—or even worse—than emissions from fossil fuels. “In our view, recent analyses using broadly accepted consensus accounting methods demonstrate those claims are just absurd,” Cooper said.

Cooper discussed the difference between the carbon lifecycles of biofuels and fossil fuels. He noted the carbon life cycle of biobased fuels is relatively rapid. Biomass feedstocks absorb CO2 from the atmosphere. That absorbed carbon is then converted into liquid fuels, which are burned, rereleasing the carbon dioxide back into the atmosphere where it is reabsorbed by the next generation of biofuel feedstock. Alternatively, when fossil fuels are burned, carbon that has been sequestered for millions of years is vented into the atmosphere. “It’s baffling to me that someone could argue these carbon cycles are somehow the same, or that one isn’t better than the other,” Cooper said. “In other words, they are pretending that plants do not absorb CO2.”

Stefan Unnasch, senior partner with Life Cycle Associates, detailed the carbon accounting approach for biofuels during his presentation, noting that the life cycle approach is the best metric for GHG emissions because it takes into account that the short-cycle carbon found in biofuels was recently removed from the air. He also addressed indirect land use change, noting the modeling methodology used in calculating indirect land use changes emissions isn’t perfect but provides a good estimation of what occurs in the real world. The alternative of requiring every farmer in the world to track land use changes is impossible, he said. “In a perfect system you would have international accounting for every hectare of land, but we don’t have that, so the alternative is to treat biofuels as short-cycle carbon and have an additional indirect land use effect, which takes into account the net shift in crops globally,” Unnasch said.

Susan Boland, a scientist with Life Cycle Associates, briefly discussed carbon intensity values determined by a recent analysis. The study reexamined the U.S. petroleum carbon intensity baseline using the latest information on the mix of petroleum feedstocks and crude oil refining and processing. The results indicate the petroleum baseline is approximately 97 grams of CO2 per megajoule, a level higher than the 93 grams of CO2 per megajoule level used by the U.S. EPA in renewable fuel standard (RFS) regulations. The study also determined that ethanol producers have significantly improved the way they make biofuel, resulting in carbon intensity scores lower than those originally assumed by EPA. According to Boland, the RFS has resulted in cumulative savings of approximately 353 million metric tons to date.

Steffen Mueller, principal economist at the Energy Resource Center at the University of Illinois at Chicago, discussed the GREET model, which is the gold standard for life cycle modeling in the U.S. He noted that although the model shows biofuels have resulted in small but positive land use change emissions, ethanol produced from corn grain and corn stover have been shown to provide substantial GHG emissions savings when compared to gasoline. The latest version of GREET shows corn ethanol in the range of 63 to 66 grams of CO2 per megajoule, significantly less than the 94 grams of CO2 per megajoule associated with gasoline. Savings are even greater for corn stover ethanol.

Finally, Wally Tyner, an energy and agricultural economist at Purdue University, addressed the difference between the method EPA and other government agencies use to account for life cycle GHG emissions and the method used by Searchinger and DeCicco.