As U.S. EPA finalizes its unprecedented rule aimed at reducing the national power sector’s carbon footprint, the agency is also focusing its aim on another greenhouse gas emitter: airlines.

EPA is expected to take a significant step toward regulating the aviation industry’s carbon footprint as soon as this week, by issuing what’s called an endangerment finding. The analysis—“a determination of whether emissions cause or contribute to air pollution which may ... endanger public health,” as EPA describes it—would set the stage for an eventual new regulation limiting airplanes’ emissions.

It’s the latest step in a lengthy, drawn-out process that has frustrated environmental groups and led to a 2012 federal court ruling ordering the agency to weigh in on the matter (ClimateWire, Sept. 9, 2014).

“The administration has already set reasonable limits on trucks and power plants, but when it comes to airplanes, EPA has not put any limits on that sector,” said Deborah Lapidus, director of the Flying Clean Alliance. “Airlines have a responsibility just like any other industry, and EPA should be holding them to that.”

A 2012 EPA report found airplanes produce 8 percent of the U.S. transportation sector’s greenhouse gas emissions. Cars and light trucks, by contrast, account for 62 percent.

But one study found that the aviation industry may triple its carbon footprint by 2050. The International Council on Clean Transportation study argued that if the world’s airplanes were their own country, they would spew more greenhouse gases than all but six other nations (ClimateWire, Jan. 5).

Biofuels, batteries or some other solution?

While many stakeholder groups expect the findings as soon as Friday, EPA isn’t publicly commenting on the timeline. Spokeswoman Liz Purchia noted that the finding is being reviewed by the Office of Management and Budget. “When the review is complete,” she said via email, “and the action is signed by the administrator, the agency will post it online for public review and comment.”

It seems clear that, regardless of the timing, EPA is on a path to regulating airplanes’ greenhouse gas emissions. The key question, then, is, how to get them lower.

In a carpeted, wood-paneled room at the National Academy of Sciences yesterday, a committee of experts from academic, military, government and industry circles tried to come up with an answer.

The session was part of a two-day conference tied to a National Research Council study aimed at developing a research agenda for reducing aviation’s carbon footprint.

The conversation among industry representatives kept coming back to two approaches—biofuels and batteries—each with its own set of upsides and flaws.

“Boeing believes that biofuels and other types of alternative fuel sources are a near-term solution to reduce carbon emissions,” Boeing senior manager Robert Stevenson told the committee. “The big challenge is getting it producible, and making sure it’s produced in a cost-effective way.”

Alan Epstein, a vice president for technology and environment at engine manufacturer Pratt & Whitney, agreed. “[Biofuels are] legal to use, and the engine manufacturers and airplane manufactures have approved those fuels for use in their vehicles,” he said. “So the only challenge to the airline is, where can they buy one at a price they can afford?”

“I don’t want to minimize the notion that a lot of research and development still needs to be done in the biofuels area,” conceded U.S. Department of Energy senior analyst Zia Haq. “These are expensive fuels.”

‘It’s going to take a while to get there, if ever’

Another more incremental option could be putting more high-powered batteries on aircraft in order to reduce the demands on carbon-spewing engines.

The emissions reductions of battery retrofits would be marginal, said Stevenson, adding that the likely benefit would be a 1 percent reduction of a plane’s emissions. “But you would be applying that 1 percent across the entire flying fleet,” he said, arguing that it could be better than waiting to develop a more effective technological breakthrough. “It’s a smaller benefit, but you’re able to spread that out over a larger number of airplanes.”

As for using batteries to ultimately propel planes through the sky, Stevenson called the prospect “dire.”

“I think the general conclusion is, unless there is a specific change in technology, a specific leap in technology, it’s going to take a while to get there, if ever,” he said.

But, as John Kinney, director of advanced technology development at General Electric, pointed out, the history of aviation is filled with those types of technological leaps. Just look at the Smithsonian’s National Air and Space Museum, where a Concorde aircraft sits yards away from an early Wright brothers model.

“We started with a 12-horsepower engine,” said Kinney. “I doubt at the time the Wright brothers thought, ‘Let’s put 300 passengers on this.’”

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500