Used Cooking Oil for Aviation Fuel

Introduction to Solution Traditional drilling for crude oil contributes an immense amount of pollution to the Earth’s atmosphere. A study conducted by Stanford University in 2018 found that “on average, oil production emitted 10.3 grams of emissions for every megajoule of crude.” In 2022, 11.89 thousand barrels of crude oil were produced in 2022—or around 69 million megajoules. This oil is used, in part, to fuel aviation, which overall, as of 2018, contributed to 2.5 percent of all carbon emissions. Further, aviation has broader climate change implications due to the release of “contrails, NOx, water vapor, sulfate aerosol gases, soot, and other aerosols.” While this is a relatively small amount compared to other contributors—such as ground vehicles—airlines have attempted to combat their contributions to the climate crisis through integrating more sustainable aviation fuel (SAF) into their oil supply. SAF is fuel made from sources including corn grain, algae, agricultural and forestry residues, solid waste and dedicated energy crops. It has been found to have “fewer aromatic components than kerosene”—the typical jet fuel—which allows them to reduce emissions of contributors other than CO2.  Recently, the used cooking oil from restaurants has become another valuable source for airlines to find SAF. In May 2022, Dallas-Fort Worth airport partnered with Neste, an oil refining company, to collect the oil used in onsite restaurants—including 5 McDonald’s locations—to convert used fry oil to airline fuel. Neste’s subsidiary, Mahoney Environmental, takes the used up oil from restaurants to convert the oil. It currently collects from 90,000 businesses in the United States, and is one of hundreds of companies that collect oil from various restaurants around the globe. In 2023, the first transatlantic commercial flight fueled 100 percent by SAF traveled from London’s Heathrow airport to New York’s JFK airport.  According to the Washington Post, the cooking oil moves through an intense process to convert it into aviation fuel; first, the grease is maintained at 140º during transit to keep its liquid consistency. Then, Neste uses a clay substance to strip out unwanted chemicals, including “sodium left over from salty foods, phosphorus and various metals.” A catalyst removes the oxygen molecules, and the “straight hydrocarbon chains are bent into spiky, irregular branches that won’t stack up and lump themselves into a solid, even at very low temperatures.” While SAF and used cooking oil help with minimizing emissions of certain fossil fuels and particles, they do not minimize emissions of CO2. Also, critics have accused SAF in airline emissions as being a greenwashing scheme, arguing that the crops used to create SAF would be better put to use by growing food. Finally, according to the World Economic Forum, “sustainable aviation fuel currently costs around four times as much as conventional jet fuel,” resulting in low incentive to replace traditional fuel production pathways with SAF.  According to Dr. Colin Murphy, our guest for this week, policy pathways and airline incentives can encourage SAF usage. About our guest Dr. Colin Murphy is the Deputy Director of the Policy Institute for Energy, Environment, and the Economy, and