Aviation makes about2% of global carbon emissions, and if you add other polluting gases, industry is responsible for about 3% of the total human-caused global warming.
One way to reduce the aviation industry's climate impact is to use new fuels. These alternatives, often referred to as Sustainable Aviation Fuels (SAFs), are produced from a variety of sources and can be used extensively on existing aircraft. They could be the key to helping this sector meet its climate goal:Net zero carbon emissions by 2050.
New directives in the EU and US are driving these new fuels and airlines are pushing for themadvertising campaignpresenting their efforts to convert fuel sources.
But while alternative fuels could be a climate solution for aviation, their actual impact depends on many factors. Here's everything you need to know about the future of kerosene and the climate.
What are SAF?
Currently, airplanes mainly burn aviation fuel, also known as kerosene - a fossil fuel with a mixture of carbonaceous molecules. The mix of these molecules can vary, but the main ingredient is single, energy-filled carbon and hydrogen chains. Alternative fuels have the same basic chemical composition as fossil fuels; The difference is that SAFs come from renewable sources.
These fuels fall into two main categories: biofuels and synthetic electric fuels.
Biofuels come from various biological sources; Some are derived from waste such as used cooking oils, agricultural waste, or landfills, while others can be made from crops grown specifically for fuel, from corn to palm trees to switchgrass.
Producing fuels from biological sources requires breaking the intricate chemical structures that plants make for energy storage. Fats and carbohydrates can be broken down into smaller pieces and purified, sometimes in existing refineries, to produce the individual chains of carbon-rich molecules that make up the main component of jet fuel.
Electric fuels (also called e-fuels), on the other hand, do not start with plants. Instead, they start with two main building blocks: hydrogen and carbon dioxide.
While both can come from different sources, the most environmentally friendly way to produce electronic fuels starts with hydrogen, produced by breaking water down into its components using renewable electricity, in addition to carbon dioxide, which has been removed from the atmosphere through direct carbon capture. Air. These are then combined and turned into electrically powered chemical reactions.
Manufacturing electronic fuels is expensive today because the process is inefficient and not yet widely deployed on a commercial scale. But experts say aviation will need to rely on them to meet its 2050 goal. This is because they are the most effective at reducing carbon emissions and are not constrained by refueling or collection logistics like fuels made from plants or waste.
So how do SAFs contribute to climate protection?
Like conventional kerosene, alternative fuels produce carbon dioxide and other emissions when burned on airplanes to generate electricity.
The difference is that SAFs can offset your carbon emissions depending on how they are made. In an ideal world, the alternative fuel manufacturing process would soak up so much carbon that when the fuel is burned, carbon dioxide emissions are essentially offset.
However, this is often far from reality. Today, the process of producing alternative fuels can be linked to carbon emissions themselves, either because of the energy required to produce them or because they affect ecosystems in ways that release carbon.
"Not all SAFs are the same," he saysMatthew Mirolo, aviation policy manager for the non-profit group Transport & Environment.
Alternative fuels fall on a spectrum in terms of reducing carbon emissions, he saysNikita Pawlenko, Head of the International Council on Clean Transportation's fuel program. On the one hand, synthetic fuels made from carbon sucked from the air by direct air capture, and whose production facilities are powered entirely by renewable electricity, will reduce emissions by almost 100% compared to fossil fuels.
At the other end of the spectrum, some agriculturally-derived biofuels can actually produce more carbon emissions than fossil fuels, Pavlenko says. This is often the case with biofuels made from palm oil, as can be the case with growing this cropdecimate rainforests. Even synthetic e-fuels can match the impact of kerosene when made with electricity from fossil fuels.
Today, most commercially available alternative aviation fuels are made from fats, oils and greases. When derived from waste sources such as used cooking oils, these fuels reduce carbon emissions by an estimated 70 to 80% compared to fossil fuels.
It's worth noting that while SAFs can achieve net-zero carbon emissions, burning fuels still produces other types of pollution, including other greenhouse gases and particulate matter. Fuels can also contribute to the formation of contrails, which trap heat in the atmosphere.
What's next for SAFs?
A few other technologies are also being discussed to reduce the climate impact on aviation, including:hydrogen- z.Bbattery powered aircraft. However, without further technological advances, these options could be limited to smaller aircraft flying shorter routesMost global carbon emissions today come from flights over 900 miles(1,500 kilometers). This is where SAFs can help. Alternative fuels are attractive to the airline industry because it is a drop-in solution that requires little modification to aircraft and airport infrastructure. (Depending on the mix of chemicals in the fuel, aircraft may need minor adjustments in the future to run at 100% SAF.)
Many net-zero plans for aviation, like that ofInternational Air Transport Associationpredict that AFSs will account for most of the industry's climate progress in the coming decades. Several in the last yeartest flightsdistributed by100% SAFspicked up. However, alternative fuels account for less than0.2% of the world aviation fuel supplyby 2022. Great progress is therefore needed to provide alternative fuels that are truly climate-friendly.
One of the biggest challenges in getting SAFs airborne is expanding the offering. Although fats, oils and greases form the basis of most SAFs commercially available today, not enough used cooking oil potato chips are eaten in the world to meet the world's need for kerosene alone. In fact, even with increased collection, waste fats, oils and greases are unlikely to account for more than 5% of the world's fuel supply, says Pavlenko.
Some new biofuels, such as those made from agricultural waste, MSW and resistant crops such as switchgrass, are beginning to appear on the market; Some plants are currently under construction or producing jet fuel from these sources around the world, and the carbon emissions savings achieved can range from 50 to 90%.
Recent policy changes in the US and European Union aim to boost the alternative fuels market.RefuelEU Aviation, an agreement signed in April, mandates that refueling at EU airports must include 2% SAFs by 2025 and 70% by 2050. The EU rule only considers SAFs from residual sources, advanced biofuels and e-fuels, not crop-derived fuels. There is also a specific goal for e-fuels to increase production.
The US, on the other hand, recently agreednew alternative fuel tax credits, aiming to help expensive options reach price parity with fossil fuels. the tax creditslast until 2027and apply to all fuels that reduce carbon dioxide emissions by at least 50% compared to fossil fuels. However, details on how the reductions are calculated have yet to be released.
Ultimately, alternative fuels represent one of the most direct ways to reduce the climate impact of aviation, but only certain types will ultimately benefit the climate. "The SAFs are a solution, but they have to be implemented well," says Mirolo. Otherwise they run the risk of becoming “a remedy worse than the disease”.