A timber harvest can often leave what's called a "slash pile" of leftovers that are usually burned. On Monday Alaska Airlines flew a number of commercial passengers across the United States by burning some of that woody biomass as fuel.

United Airlines began using a mix of conventional jet fuel and biofuel made from feedstocks, agricultural waste and some natural oils in regularly scheduled flights earlier this year, but Monday's flight appears to be the first with fuels derived from wood.

The flight from Seattle to Washington, D.C. burned a 20 percent blend of alternative jet fuel made from stumps and branches leftover after timber harvest or forest thinning in the Pacific Northwest. U.S. Department of Agriculture funding and a partnership involving Washington State University (WSU), the Northwest Advanced Renewables Alliance (NARA) and Gevo, Inc.led to the development of the sustainable fuel.

Gevo has a patented alcohol-to-jet-fuel process that it adapted to convert wood waste into isobutanol and then convert to jet fuel meeting the international standard used for commercial flights. For this demonstration, excess woody leftovers from privately managed forests owned by private industry and local Native American tribes were sent to Gevo's facilities in Missouri and Texas to be transformed to fuel.

A sample of sustainable jet fuel made from woody forest leftovers Alaska Airlines

Air travel using conventional jet fuel has an outsized carbon footprint that contributes to climate change, motivating researchers and the aerospace industry to look for "greener" alternatives like biodiesel, diesels made from natural waste oils and even "solar" fuel made from air and water. Boeing is also participating in a similar effort to create fuels from forest waste.

According to WSU, if every Alaska Airlines flight from Seattle used the same 20 percent blend, the resulting reduction in in greenhouse gas emissions would be equivalent to taking about 30,000 cars off the road for a full year.

Sources: Gevo, Alaska Airlines, Washington State University