SAF 101: Feedstocks
As the aviation industry works to decarbonize, sustainable aviation fuel (SAF) has become one of the most promising tools to cut emissions without grounding air travel. Produced from renewable and waste-derived resources, SAF offers a potential life-cycle greenhouse gas (GHG) reduction of up to 85% compared to conventional jet fuel. But not all SAF is created equal — and the sustainability and carbon performance of the fuel largely depend on one critical factor: feedstocks.
From used cooking oil and beef tallow to purpose-grown crops and even captured carbon, feedstocks form the foundation of SAF. Their source, availability, and emissions profile determine how “sustainable” the fuel truly is. This article explores the landscape of SAF feedstocks, their environmental trade-offs, and what it will take to scale production while keeping carbon intensity low.
What Is a Feedstock?
A feedstock is a raw material used to produce another product. In the case of fossil fuels, crude oil is the feedstock. For SAF and other biofuels, feedstocks can include everything from vegetable oils and animal fats to algae and municipal solid waste.
Feedstocks for SAF are broadly categorized based on their origin and economic value. The International Civil Aviation Organization’s CORSIA framework divides them into five types:
- Primary products (e.g., carinata oilseed) are intentionally grown to produce biofuels or other products and have significant market value.
- Co-products and by-products (e.g., molasses) are secondary outputs of other production processes.
- Wastes (e.g., used cooking oil) and residues (e.g., agricultural waste) have low or no economic value and often face disposal challenges.
Using waste-based or low-value feedstocks is generally preferable from a sustainability and carbon intensity standpoint. That’s because such feedstocks avoid land-use changes, offer GHG reductions without competing with food systems, and use materials that would otherwise go to waste.
How Feedstocks Become SAF
Different SAF production technologies require different types of feedstocks. Today, three main conversion pathways dominate:
- HEFA (Hydroprocessed Esters and Fatty Acids): HEFA is the most commercially mature SAF technology. It uses fats, oils, and greases as feedstocks — everything from soybean and canola oil to used cooking oil and animal fats. Through hydrogenation and refining, these feedstocks are converted into a fuel that is chemically indistinguishable from conventional jet fuel.
- AtJ (Alcohol-to-Jet): This pathway uses ethanol — sourced from corn, sugarcane, or waste biomass — as the starting point. The ethanol is chemically converted into SAF through the oligomerization process. AtJ offers flexibility in feedstock sourcing but is still emerging at commercial scale.
- PtL (Power-to-Liquid): PtL fuels are made by synthesizing captured CO₂ with green hydrogen to create liquid hydrocarbons. This pathway represents a long-term vision for fully circular, fossil-free aviation fuel, but it is still in the very early stages.
Feedstock and Carbon Intensity: What’s the Link?
Carbon intensity (CI) is a measure of the total GHG emissions associated with producing and using a fuel, expressed as the amount of carbon dioxide (or equivalent emissions of another gas) produced per unit of energy (e.g., grams CO₂e/MJ). Carbon intensity includes emissions from feedstock cultivation or collection, transport, processing, and combustion. Lower carbon intensity means higher life-cycle carbon reductions from using the fuel in place of traditional fossil fuels.
Feedstock selection plays a major role in CI:
- Waste-derived feedstocks like used cooking oil and beef tallow generally have low carbon intensity because they avoid emissions associated with cultivation and land use.
- Virgin vegetable oils, especially those associated with deforestation or land-use change, can have significantly higher CI scores.
- Emerging feedstocks like algae and cover crops hold promise for ultralow CI due to carbon sequestration potential or minimal land-use impact.
At World Energy, we prioritize feedstocks with low carbon intensity, short transport distances, and minimal processing needs. Our primary feedstock today isbeef tallow, a domestically sourced waste product, which offers both low CI and reliable supply.
Feedstock Supply: Is There Enough?
The SAF conversation often prompts the question of whether there are enough feedstocks to meet demand. While limitations exist, the US Department of Energy projects that the domestic supply of feedstocks like fats, oils, greases, residues, and dedicated feedstock crops could be sufficient to support US SAF demand while also supplying other low-carbon fuels.
That said, no single feedstock or technology can meet the need alone. We need a diverse mix of SAF production pathways — with HEFA forming a foundational part of the solution in the near to medium term, and advanced technologies coming online over time.
Looking Ahead: The Future of SAF Feedstocks
World Energy is actively investing in the next generation of feedstocks to build long-term supply security and further reduce carbon intensity. Some of the most promising developments include:
- Cover crops like carinata, pennycress, and camelina: These oilseeds can be planted between food crop cycles, helping regenerate soil while producing SAF feedstock. They’re already nearing commercial volumes in South America and parts of the United States and are compatible with HEFA processing technology.
- CO₂-derived fuels: Capturing carbon from industrial sources and combining it with green hydrogen could unlock vast SAF potential without relying on biomass.
- Innovative materials: Feedstocks like algae, insect oil, and oleaginous yeast may one day offer high yields with low environmental impact — but most are still far from commercial readiness.
Sustainable aviation fuel is a powerful tool in the decarbonization of flight — but its effectiveness depends on what goes into making it. World Energy is committed to leading with integrity — choosing feedstocks that reduce carbon intensity, increase efficiency, and maximize sustainability. Innovating to improve what’s available today and expand options for tomorrow is the surest way to support the aviation industry on its path to net zero.
