Under Pressure To Revise Estimates, EPA Mulls Lifecycle Biofuel GHGs

Source: By Stuart Parker, Inside EPA News • Posted: Sunday, March 6, 2022

As EPA comes under growing pressure to increase its estimates of how much greenhouse gas emissions biofuels save over their lifetime, the agency is holding consultations that could result in changes that may boost programs encouraging biofuels use such as the renewable fuel standard (RFS), which are now limited by current GHG estimates.

EPA held a virtual workshop on biofuels’ lifecycle GHG emissions Feb. 28 and March 1, during which officials and a host of experts weighed different techniques to determine the properties of various biofuels, including corn ethanol, which remains the country’s dominant biofuel.

Agency officials did not support changes to EPA’s methodology, but invited an ongoing conversation with stakeholders on the controversial topic. “We are not going to make a decision today,” one EPA staffer told the meeting, adding that the agency encourages the public to “continue to supply input.”

At issue is EPA’s existing model to estimate GHG emissions from biofuels, which industry advocates say is decades out of date and contradicts newer estimates from the Department of Energy (DOE), California air regulators, Harvard University and others.

One leading model is the DOE Argonne National Lab’s Greenhouse Gases, Regulated Emissions, and Energy Use in Technologies (GREET) model.

Such newer models find corn ethanol produces GHG savings relative to unblended gasoline in excess of 40 percent. In comparison, the RFS now requires that corn ethanol attain a 20 percent GHG cut, in line with EPA modeling that estimates much lower GHG reductions.

The “best academic research, confirmed by federal agencies, shows homegrown ethanol and biomass-based diesel cut total, lifecycle climate emissions by 46-74 percent,” said a coalition of farm and biofuels groups including Growth Energy, National Farmers Union and Renewable Fuels Association in a March 2 joint statement calling for increased biofuel use.

While EPA has stuck by its earlier, lower estimates of GHG savings, the Department of Agriculture (USDA) has endorsed the GREET model. Various pro-ethanol lawmakers of both parties have urged EPA to adopt GREET, with some advancing draft legislation to achieve this.

The issue is crucial to the future of the RFS. In 2023, the program’s statutory targets for biofuel blending expire, and EPA then will have greater freedom to set blending levels itself. Higher estimates of biofuels’ GHG benefits would help justify increases in biofuel blending.

EPA is due to propose and finalize this year a “set” rule to establish blending mandates for at least 2023 and possibly other years as well. The agency has already proposed an increase in blending for 2022, but has yet to finalize that overdue rule.

Meanwhile, some biofuel supporters have called for the creation of a national low-carbon fuel standard (LCFS) that would allow biofuels to compete with other fuel types, including electricity, on a “technology-neutral” basis. California already operates an LCFS, under which much fuel demand is satisfied by biofuel. Others have advocated a higher national octane standard that would likely spur use of more biofuel.

The Biden administration plans to rely heavily on biofuels, including potentially ethanol, to make sustainable aviation fuel (SAF) to reduce carbon emissions from the aviation sector. And biofuels advocates are pressing both nationally and on a state-by-state basis for year-round use of 15 percent ethanol fuel (E15), which is currently prohibited in many states under federal court order.

Land-Use Change

Various presenters at the EPA workshop addressed land-use change, a core issue in lifecycle analysis of biofuels’ GHG emissions. Critics of the RFS have blamed the policy for conversion of land to corn ethanol or soybean production, with adverse environmental consequences.

“We really need to understand how much land is being converted to agriculture, what type of land is being converted to agriculture, and what are the emissions that result from making . . . these changes,” said EPA staffer Sharyn Lie.

In a recent study, researchers at the University of Wisconsin claimed that land-use change could mean the RFS leads to higher GHG emissions, not reductions as the Clean Air Act requires.

But speakers at the conference refuted this, pointing to numerous inaccuracies in estimates of cropland that are based on satellite imaging. For example, Dev Shrestha, a professor of chemical and mechanical engineering at the University of Idaho, said that overall, agricultural land has declined in the United States.

An “automated image classifier” for satellite data “has [an] average error rate of 28% compared to human classification when tested over various geographical areas,” Shrestha said.

Zia Haq, a DOE senior analyst, questioned whether various different models should be reconciled. These include EPA’s methodology, GREET, methods used by the California Air Resources Board, and also the International Civil Aviation Organization’s (ICAO) Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA).

Jim Hileman, chief scientific and technical advisor for environment and energy at the Federal Aviation Administration (FAA), called the CORSIA methodology “a rigorous means to do lifecycle accounting.”

“We are taking a holistic approach to address aviation’s impact on climate change,” Hileman said. Sustainable aviation fuels “are central to this approach — critical to reducing [carbon dioxide] emissions from aviation in near, mid, and long term.”

William Hohenstein, director of the Office of Energy and Environmental Policy within USDA’s Office of the Chief Economist, outlined increases in productivity that have grown the supply of biofuel feedstocks including ethanol.

Much of the increase has been due to farmers using more-efficient methods, according to Hohenstein’s presentation, with corn acreage relatively stable since 2007, but soybean production showing a marked increase since then. Total cropland has declined slightly since 2007, he said.

“Farmers decided to intensify management, improve yields, and return land to production to meet increasing demand,” Hohenstein said. “Potential remains to continue to increase yield and intensify production, especially in regions that are well below production potential.”