Later this summer, one United Airlines flight will be routine in all ways but one. The plane, heading from Los Angeles to San Francisco, will be flying on 70 percent traditional jet fuel—and 30 percent biofuel. And this is no one-off gimmick: At first, just four to five flights a day will be flying greener, but after about two weeks, the biofuel—made of food scraps, farm waste, and animal fat—will be added to the airline's overall fuel supply.

This isn't United Airlines' first brush with alternative energy; they've been experimenting with biofuel in test flights since 2009, and in 2011 the airline became the first in the country to partially power a commercial flight with a biofuel when it flew a Boeing 737-800 from Houston to Chicago on a blend of regular fuel and algae-based biofuel. That flight was ground-breaking, but primarily just a publicity stunt—at the time, biofuel production was far too costly to constitute a reasonable alternative.

Now, with newer biofuel technology and a $30 million investment in one of the largest producers of aviation biofuels, Fulcrum BioEnergy, United is ready to make a more permanent commitment to the alternative energy. (The first flight this summer will use fuel from a different company, AltAir Fuels.)

Switching from traditional fuel to biofuel has two primary benefits for the environment. First is the drastic cut in carbon emissions, which airlines have been pressured to address for years. Although the biofuel will represent less than half the total fuel used by the airline at first, Fulcrum says that its technology can cut an airline’s carbon emissions by 80 percent compared with traditional jet fuel—an amount that adds up over hundreds and thousands of flights. This will help the airline industry meet its publicized goal to cut greenhouse gas emissions to half of their 2005 levels—when planes emitted 318.5 million metric tonnes of carbon—by 2050.

Additionally, biofuel companies make use of the massive amount of organic waste humans produce: Studies have shown that 30 percent of the food produced in the U.S. is never eaten and makes up about 20 percent of landfills. Biofuels give this organic trash a new life as sustainable energy.

There are some concerns that biofuel isn't cost efficient or readily available enough to use regularly, but Fulcrum is pushing back against those claims. E. James Macias, Fulcrum’s chief executive, told The New York Times that his company could produce biofuel for "a lot less than" $1 a gallon, which would give airlines yet another incentive to make the switch: United bought its jet fuel for $2.11 a gallon, on average, in the first quarter. And in order to keep up their supply, Fulcrum has inked 20-year agreements with municipal waste management companies.

Although United Airlines will break barriers with their biofuel-powered flight this summer, they're not the only company looking to incorporate sustainable energy systems. British Airways is building a biofuel refinery near London’s Heathrow Airport, which will be completed by 2017; Alaska Airlines aims to use biofuels for flights from at least one of its airports by 2020; and Southwest Airlines has plans to purchase about three million gallons a year of jet fuel made from wood residues from Red Rock Biofuels. All of this is encouraging news coming from an industry that is one of the fastest-growing sources of carbon pollution around the world.

[h/t Grubstreet]