Some airlines are stepping away from kerosene-based jet fuel to an unlikely alternative: used cooking oil. The kitchen staple was first used on a short 2011 KLM Royal Dutch Airlines passenger flight but has since powered a transatlantic Virgin Atlantic flight. The now historic Virgin flight was a test-case to show that flights can solely run on this cooking oil fuel, though most commercial flights use a blended ratio. The greasy fat is gathered from hotels and fast-food chains like McDonalds and Burger King in the hopes of playing a part in the aviation industry’s goal of net-zero emissions by 2050. So far, sustainable aviation fuel, or SAF, has powered over 360,000 commercial flights, according to the U.S. Department of Energy.
There are many types of SAFs ranging from crop-based biofuels to alcohol-based, but those made from waste products like used cooking oil have a lower carbon footprint. The cooking oil is cleaned and processed to resemble traditional flight fuel and planes generally don’t need to be converted to use it. SAF is estimated to reduce flight emissions by as much as 85% but some environmental organizations say that, depending on the source, SAF might not be as climate-friendly as it seems.
On top of the emissions reductions, research by the Poznan University of Technology and Air Force Institute of Technology indicates this fuel reduces particulate matter released from flights. Air quality changes due to aviation are estimated to cause roughly 8,000 deaths every year.
The benefits of SAF sound promising, so why aren’t more airlines using this to mitigate the industry’s annual contribution of 2.5% emissions?
One reason is scale: aviation requires massive amounts of fuel and cooking oil gathering efforts — even if ramped up — likely wouldn’t be enough to meet this demand. “There’s only so much of that type of oil in the world, and there’s even less of it that can be sourced sustainably,” Joshua Heyne, director of Washington State University’s Bioproducts, Sciences, and Engineering Lab, told Melissa Hobson for National Geographic. Another is cost, SAFs are more expensive to produce than traditional fuel.
To fill this gap, other sources like crops are used, which scientists and environmental organizations say is the opposite of sustainable. Food systems currently contribute around a quarter of greenhouse gas emissions while nearly 10% of people globally experience hunger. Growing more crops to feed flights, not humans would “increase net emissions while diverting valuable cropland away from food production,” according to The World Resources Institute.
Europe has avoided crop-based fuels for this reason while the U.S. is still toying with the idea. President Trump seeks to continue Biden’s tax credits on SAFs which might mean further expansion of unsustainable crop-based fuels.
“Using crops like corn and soybeans to produce fuel instead of food not only increases food prices and global hunger, it spurs farmers around the world to tear down more forests and plow up more grasslands to create new farmland to replace the lost food,” Michael Grunwald, author of “We Are Eating the Earth: The Race to Fix Our Food System and Save Our Climate,” wrote for Yale Environment 360.
Although the cooking oil used to fry your takeout might be a promising way to bring down aviation emissions, it faces challenges to meet global demand, while other sources of SAFs may negate the whole concept of sustainability altogether.
