On the opposite finish of the spectrum, some crop-based biofuels can truly produce extra carbon dioxide emissions total than fossil fuels, Pavlenko says. That’s incessantly the case for biofuels constructed from palm oil, since rising that crop can decimate rainforests. Even artificial e-fuels can method the impression of jet gas in the event that they’re produced utilizing electrical energy from fossil fuels.

Right this moment, most commercially obtainable various jet fuels are constructed from fat, oils, and greases. In the event that they’re derived from waste sources like used cooking oils, these fuels scale back carbon dioxide emissions by roughly 70% to 80% in contrast with fossil fuels.

It’s price noting that whereas SAFs can method net-zero carbon dioxide emissions, burning the fuels nonetheless produces different varieties of air pollution, together with different greenhouse gases and particulate matter. The fuels may contribute to formation of contrails, which entice warmth within the ambiance. 

What’s subsequent for SAFs?

There are just a few different applied sciences on the desk for reducing local weather impacts in aviation, together with hydrogen– and battery-powered planes. Nonetheless, with out additional technical progress, these choices could also be restricted to smaller planes flying shorter routes, and most international carbon dioxide emissions right now come from flights over about 900 miles (1,500 kilometers). That’s the place SAFs may assist. Various fuels are engaging for the aviation trade as a result of they’re a drop-in answer, requiring little adjustment of plane and airport infrastructure. (Planes would possibly want small changes to run on 100% SAFs sooner or later, relying on the combination of chemical substances within the gas.)

Many aviation net-zero plans, just like the one printed by the Worldwide Air Transport Affiliation, assume that SAFs will make up the vast majority of the trade’s local weather progress within the coming a long time. Over the previous yr, a number of take a look at flights powered by 100% SAFs have taken off. Nonetheless, various fuels made up lower than 0.2% of the worldwide jet gas provide in 2022. So there’s quite a lot of progress wanted to produce various fuels which are truly useful for the local weather.

One of many essential challenges to getting SAFs into the skies is increasing the provision. Whereas fat, oils, and greases are the premise of most commercially obtainable SAFs right now, the world doesn’t eat sufficient french fries for used cooking oils to fulfill international jet gas demand alone. In truth, even with elevated assortment, waste fat, oils, and greases in all probability gained’t present greater than 5% of worldwide jet gas provide, Pavlenko says.

Some new biofuels, like these constructed from agricultural residue, municipal strong waste, and hardy crops like switchgrass, are beginning to enter the market; just a few services are below building or producing jet gas from these sources worldwide, and the carbon dioxide emission financial savings they obtain can vary from 50% to 90%.

Latest coverage strikes in each the US and the European Union are geared toward boosting the marketplace for various fuels. RefuelEU Aviation, a deal finalized in April, requires that gas provide at EU airports embrace 2% SAFs by 2025 and 70% by 2050. The EU rule will solely rely SAFs from waste sources, superior biofuels, and e-fuels, not crop-derived fuels. It additionally has a selected goal for e-fuels that’s geared toward boosting their manufacturing.

The US, alternatively, lately handed new tax credit for various fuels, geared toward serving to costly choices attain worth parity with fossil fuels. The tax credit final till 2027 and apply to any gas that reduces carbon dioxide emissions by no less than 50% in contrast with fossil fuels, although the main points on how reductions are calculated haven’t been launched but.

In the end, various fuels current one of the easy pathways to reducing the local weather impacts from aviation, however solely sure varieties will find yourself benefiting the local weather. “SAFs are an answer, however they should be very correctly performed,” Mirolo says. In any other case, they danger changing into “a remedy that’s worse than the illness.”