SAFs are nearly chemically identical to traditional fossil-based jet fuels and can be used seamlessly in conventional aircraft engines. What makes them ‘sustainable’ is the difference in their production: SAFs are made from sustainable sources like biomass or waste oils, unlike conventional jet fuels derived from fossil hydrocarbons.

What makes SAFs NET-ZERO?

SAFs emit CO2 when burned, which might raise the question: How can they be net-zero in terms of CO2 emissions? The answer lies in how they fit into the carbon cycle.

The carbon cycle is a continuous process where CO2 move between the atmosphere and Earth. It is a closed system, so the total carbon stays the same. Carbon from the atmosphere is absorbed as plants and trees grow, animals eat them, and then release CO2 when things decay. Indeed, it is a symbiotic balance of carbon release and absorption without additional CO2 entering the closed system.

In contrast, burning fossil fuels releases CO2 that has been out of the carbon cycle for millions of years, thereby adding new carbon to the atmosphere. 

SAFs are carbon neutral because they are made from carbon already in the cycle. For instance, plants, which grow by capturing carbon from the atmosphere and later release carbon when they decompose, are used to make SAFs. SAFs release carbon when burned, but they don’t add new carbon to the cycle because they are made from carbon that was already part of that cycle.

SAFs: Composition and Benefits

SAFs are low, zero, and even negative emission alternatives to conventional jet fuel, derived from sustainable sources like waste products, agricultural residues, and renewable energy. Chemically similar to traditional jet fuel, SAFs offer the advantage of a significantly lower carbon footprint.

The production of SAFs involves various methods, including refining waste materials, converting gases into liquids, and using electricity to generate liquid fuels. Current technologies enable SAFs to reduce greenhouse gas emission in the range of 26.1% to 94.2% [47]. Evolving SAF production technologies, particularly when specific feedstocks are combined with carbon capture techniques, can even achieve negative emissions, effectively removing more carbon from the atmosphere than they emit during their lifecycle.

Aviation faces a distinct challenge in its pursuit of decarbonization compared to other transport sectors like automotive and maritime. Aircraft require fuels with high energy density to overcome the forces of gravity, making every ounce crucial. This necessity for high-energy-density fuels is what makes SAFs particularly suitable for aviation, as they meet the energy requirements while offering a more sustainable alternative.

Drop-In Solution

SAFs serve as a “drop-in” solution, seamlessly compatible with existing aircraft engines without needing modifications. This compatibility allows airlines to adopt SAFs promptly, bypassing the need for new aircraft development or extensive infrastructural changes. SAFs are already in use, with many aircraft engines certified to operate with up to 50% SAF blend, demonstrating their immediate applicability and versatility. Looking ahead, it is expected that aircraft will soon be certified for 100% SAF use, and indeed, some aircraft have already successfully flown using 100% SAF.

SAFs present a viable and scalable option for reducing aviation’s carbon footprint in the short to mid-term. As a sustainable fuel, they offer a practical solution for the aviation industry to progress towards emission reduction.

INSIGHT: Visualizing SAFs in the Carbon Cycle

Imagine the atmosphere filled with carbon dioxide. You plant an acorn, and it sprouts into a mighty oak tree. As it grows, it absorbs carbon dioxide from the air, using it to build its trunk, branches, and leaves.

This carbon, once floating in the atmosphere, is now locked within the tree’s structure. Eventually, the tree reaches the end of its life and begins to decompose, a process that would naturally release the stored carbon back into the atmosphere, completing the carbon cycle.

Now, enter SAFs. Instead of allowing the tree to decompose and release its carbon, we intervene. We harvest the tree and convert it into a fuel suitable for aviation. When this fuel is burned in an aircraft’s engine, it releases carbon dioxide. However, this is the same carbon that the tree had previously absorbed from the atmosphere. Thus, there’s no increase in atmospheric carbon levels – we’ve simply borrowed what was already there and returned it. This circular process of absorbing and releasing without adding new carbon makes SAFs a sustainable choice for aviation, aligning with the natural carbon cycle yet not contributing to increased atmospheric