EPA warns corn-based ethanol may not be green

The US government’s own scientists questioned whether corn-based ethanol is better for the environment than traditional petroleum-based fuels, nearly two decades after Congress first mandated its use.

The EPA’s Science Advisory Board — a panel with dozens of experts that reviews how the agency uses research and technical information — agreed to advance a report questioning ethanol’s carbon intensity and urging more study.

The board voted to adopt the draft, subject to minor revisions and approval from its chair, setting up its final release in coming weeks. While some panel scientists emphasized the group was not prejudging the results of more research, its decision is a blow to ethanol advocates championing a greater role for the alcohol as a cleaner option for fueling cars, trucks and planes. The action comes just as the US. Treasury Department develops guidance that will help dictate what products qualify for a tax credit meant to drive more sustainable aviation fuel.

At issue is a federal requirement that when EPA quotas compel renewable fuels, they generate no more than 80% the greenhouse gas emissions of gasoline and diesel across their entire life cycle — from the farm to final combustion. But the agency’s science advisers said there’s uncertainty about “how much cropland has expanded to grow corn for ethanol” as a result of annual biofuel-blending quotas under the US’s Renewable Fuel Standard.

Biofuel advocates warned the board against the move, arguing there’s a wealth of data showing that less US land is being used to produce corn as yields improve and that the end product is far better for the environment than the petroleum-based fuels it’s displacing.

The board suggested the EPA could better target incentives to the cleanest production — such as ethanol made at factories with carbon-capture technology trapping on-site emissions. Uncertainty around ethanol’s life-cycle emissions “might be reduced if the RFS allowed differentiated incentives or constraints,” the draft report said.