Environmentalists have long believed that commercial flying damages the climate with the massive amount of CO2 that passenger jets emit globally; air travel accounts for about 2.5 percent of worldwide carbon dioxide emissions. The problem is rooted in the burning of fossil fuels, a process that essentially takes carbon buried beneath the Earth’s surface and releases it into the atmosphere. The process is thought to contribute to global warming.

Instead of adding to the amount of carbon in the air, the Oxford experiment would result in a “carbon-neutral” emission by aircraft. Essentially, a jet would extract the gas from the air while on the ground and re-emit it via combustion while in flight.

“We need to reuse the carbon dioxide rather than simply burying or trying to replace it in the aviation industry,” said Peter Edwards, a professor of inorganic chemistry at Oxford and a lead researcher on the project. “This is about a new and exciting, climate-conscious, circular aviation economy.”

Typically, jet fuel is derived from crude oil. It is a hydrocarbon, or nonrenewable organic compound consisting solely of hydrogen and carbon atoms. Jet fuel is similar to gasoline in that both come from fossil fuels. However, they go through different refining processes, which results in jet fuel being heavier, with a lower freezing point and more carbon atoms.

When the fuel is burned during travel, the hydrocarbons are released into the atmosphere as carbon dioxide. Oxford researchers investigated to reverse-engineer that process, turning the gas back into a usable liquid via “organic combustion.”

The biofuel industry was blossoming before the pandemic rattled the sector as Americans faced travel restrictions and a spreading respiratory pathogen, the novel coronavirus.

Global biofuel output hit record levels in 2019, and growth was projected to be 3 percent in 2020 before the coronavirus sharply reduced international travel. The sector could begin bouncing back to pre-pandemic levels in 2021, if travel increases and global fuel demand rebounds, the International Energy Agency said in a November report. However, if oil prices remain low, the biofuel sector could undergo a production pullback and face a negative longer-term outlook.

The two most common types of biofuels on the market are ethanol and biodiesel produced from a wide variety of vegetable oils and animal fats.

In the lab, Oxford researchers used oxides of iron, manganese and potassium as a catalyst, and added citric acid. They then introduced carbon dioxide from a canister. Heating this mixture to 300-degrees in flowing hydrogen created a liquid that they believe would act like jet fuel if produced at scale.

From here, the vision is to figure out how much CO2, hydrogen and catalyst would be required for a long flight. Then, the goal is to produce that amount, Edwards said. If successful, the development could join a long list of other aviation fuel alternatives meant to directly replace conventional jet fuel.

There has been some push by the airline industry to implement environmentally sustainable practices for years. In 2016, United Airlines kicked off an initiative to use biofuel to power flights between Los Angeles and San Francisco. On Dec. 10, it pledged to reduce all its greenhouse gas emissions by 2050, echoing broader industry targets.

Oxford researchers claim their novel technique for creating jet fuel would be cheaper than other biofuel methods that undergo a long process and rely on cobalt.

Aviation fuel experts outside of the experiment champion the idea but wonder whether it will be feasible at scale since it’s more complicated to extract carbon dioxide from the air than from a canister.

“Getting carbon dioxide directly from the air is a very difficult process because it’s so dilute. There’s so little carbon dioxide in the air, it’s only 400 parts per million or .04 percent,” said Terry Mazanec, a natural-gas chemist who is the chief operating officer at the bioenergy firm Lee Enterprises Consulting.

“While this is an interesting new development, the overall process isn’t something that’s going to be easily picked up and commercialized.”

The Oxford team wants within three years to complete a transatlantic trip based on its artificial fuel.