Making Flying Cleaner

Flying is just about the most polluting thing many of us do.

According to Google Flights, a nonstop flight from New York to San Francisco produces, on average, more carbon dioxide per economy class passenger than a person living in Cameroon does in a year, as my colleague Hiroko Tabuchi wrote recently.

This week the Biden administration announced new moves to make aviation cleaner, proposing guidelines for how fuel producers can qualify for tax credits as part of a program to increase production of more sustainable jet fuel, my colleagues Max Bearak and Dionne Searcey wrote.

The guidelines are not yet final, but what caught my attention is that they allow corn-based ethanol to be part of the answer. Among experts, ethanol can be divisive and its environmental benefits are fiercely debated, even two decades after the U.S. started mixing it with gasoline.

Today, I want to lay out why the aviation industry generates so much pollution and explain the debate over ethanol.

Air travel is responsible for 3 percent of global carbon emissions, and those emissions are growing faster than those of rail, cars and trucks, or ships. Finding a way to lower that number is one of the most difficult pieces of the energy transition, in part because the technology isn’t quite there yet to provide a solution on the scale we need.

Airplanes, Hiroko told me, also emit other pollution like nitrogen oxide and soot, and form contrails, all of which warm the planet further. Scientists estimate that the net warming effect of these may be up to three times as great as the warming caused by aviation’s carbon dioxide emissions alone.