We've heard about airplanes powered by cooking oil, but what about aviation fuel made entirely from human excrement? Firefly Green Fuels, an aviation company based in Gloucestershire, United Kingdom, has done just that—and, unsurprisingly, the prospect of planes propelled by human waste is grabbing attention, as reported by CNN.

Although sustainable aviation fuel (SAF) has been around for a while, the concept of utilizing wastewater is a recent innovation. So, could this truly be the future of air travel?

Commercial aviation contributes to approximately 2.5% of global carbon emissions, playing a role in climate change.

Efforts to reduce the industry's impact are underway, with the development of electric and hydrogen-powered planes. However, the technology is still far from powering long-distance passenger flights.

Instead, the industry is looking to use SAF – the International Air Transport Association (IATA) estimates that it could contribute up to 65% to the emission reduction needed for aviation to reach net-zero by 2050.

SAF burns like conventional aviation fuel, producing the same amount of emissions as an airplane flies, but it has a lower carbon footprint throughout its entire production cycle, because it is typically made from plants that absorbed carbon dioxide (CO2) from the atmosphere when alive. Or, in the case of wastewater, it is made from plants and other foods that have been consumed by humans and passed through the digestive system. The absorbed CO2 is released back into the atmosphere when SAF burns, whereas burning fossil fuel-derived aviation fuel emits carbon that was previously locked away.