Is climate-friendly flying possible? Biden administration places a big wager.

Senior White House officials said the program would clean the airline industry while bringing prosperity to rural America.

But environmental groups and some scientists expressed reservations about the plan, which would award subsidies based on a scientific model that has previously been used to justify incentives for corn-based ethanol. Studies have found the gasoline additive is exacerbating climate change.

The new tax credits, created through President Biden’s signature climate law, are meant to spur production of jet fuels that create no more than half the emissions of the petroleum-based product. Each gallon of such fuel qualifies for a tax credit up to $1.75 per gallon.

“The concern is they will end up subsidizing fuels that take an enormous amount of land to produce,” said Tim Searchinger, a senior research scholar at Princeton University. In addition to corn-based ethanol, he said, the new subsidy could spur massive new production of biofuels made from vegetable oil, with farmland currently being used to grow food replaced with crops harvested for jet fuel production.

That, in turn, could unleash more deforestation around the world as land is cleared to backfill food production displaced in the United States, Searchinger said.

Administration officials said on a call with reporters Thursday that they are carefully weighing such concerns. Agencies are in the process of updating the scientific model for gauging climate friendliness of jet fuels, they said, and it will be revised to factor in the emissions impact of cropland converted from food to fuel production. Federal agencies plan to complete their revisions by March 1.

“The Sustainable aviation fuel industry is a potential 36 billion gallon industry that for all intents and purposes is just getting started,” Agriculture Secretary Tom Vilsack said on the call. “This is a big, big deal.”

The announcement thrusts the complicated politics of ethanol and biofuels into an election year. Subsidies for such products are hugely popular in some Midwestern swing states, and industry players are lobbying for maximum flexibility in what products could qualify for the new jet fuel subsidies.

Vilsack said the administration is eager to make eligible as many fuels derived from agricultural products as possible, including those made using nascent technologies such as “climate smart” agriculture and machinery to capture and store emissions. The effectiveness of such technologies is in dispute among scientists and climate economists.

“There are some who argue that when discerning the climate benefits of your fuel you should be allowed to take credit for carbon a crop absorbs and deposits into the soil,” said Mark Brownstein, a senior vice president overseeing energy transition work at the Environmental Defense Fund. “In theory, that make sense. But it turns out it is very hard in practice to document whether that is happening and the degree to which the carbon stays permanently stored in the ground.”

Jet travel is one of the most vexing climate problems. While it accounts for only two percent of U.S. greenhouse gas emissions, it is among the most stubborn of any sector. Those emissions are on the rise as the travel industry recovers from the covid-19 pandemic.

Unlike automobiles, jumbo jets cannot run on batteries. The immense amount of energy they consume makes electrification possible only for small planes making short trips. So the industry has turned to jet fuels that can run existing engines but release fewer emissions when burned. These products, which are typically mixed with traditional jet fuel, are marketed as “sustainable aviation fuel.”

Last month, Virgin Atlantic made the first transatlantic flight powered entirely by sustainable aviation fuel. A company news release claimed the flight emitted 70 percent less carbon than a flight powered by petroleum-based jet fuel.

But sustainable aviation fuel accounts for less than one percent of the jet fuel burned in the world. At the moment, much of it is made with waste products such as animal fats or french-fry grease. But the supply of such feedstocks will be exhausted quickly as airlines shift away from petroleum to meet their climate targets.

The United States and other countries are scrambling to ramp up production of low-carbon jet fuels that can be produced on a larger scale, aiming to not just meet climate goals, but also become dominant players in a fledgling industry with huge growth potential. Vilsack said there is a need for 36 million gallons of the fuel, which is more twice the amount of corn-based ethanol the U.S. produces annually. This new industry, he said, will support 400,000 jobs.

“You can do the math,” Vilsack said. “This is a tremendous opportunity.”