HEFA — hydroprocessed esters and fatty acids — accounts for approximately 85–90% of all SAF produced globally. Of the estimated 1.9–2.4 million tonnes of SAF output in 2025, roughly 1.7–2.1 million tonnes comes from HEFA plants processing used cooking oil, animal tallow, and other waste lipids. It is the only fully commercialised SAF pathway: proven at scale, ASTM-certified, CORSIA-eligible, and compatible with existing airport infrastructure. It is also approaching a hard ceiling. Global sustainable supply of waste and residue oils tops out at approximately 4–5 million tonnes per year. SAF demand under current mandates will require 6–8 million tonnes by 2030. The gap — 2–4 million tonnes, or a 30–50% production shortfall — cannot be closed by HEFA alone.

This matters now because the capital decisions shaping 2030 supply were made in 2022–2024. Most HEFA capacity announced for the end of the decade is already under construction. The window for course correction is closing, and the next-generation pathways that could fill the shortfall — ATJ, Fischer-Tropsch gasification, power-to-liquid — are years behind the timeline the targets assume.

How HEFA Became Aviation’s Default SAF Pathway

HEFA dominates for a simple reason: it works. The technology converts lipid feedstocks — fats, oils, and greases — into drop-in jet fuel through hydroprocessing, a catalytic process already used at scale in petroleum refining. Production costs run €1,461–1,800 per tonne (EASA 2024 data), making it the cheapest SAF pathway available. No specialised blending equipment is required at the airport. Regulatory approval is established across every major jurisdiction.

New HEFA capacity continues to come online, and the US Department of Energy’s 2024 Pathways to Commercial Liftoff report projects HEFA at 66% of 2030 SAF production, with ATJ at 23% and all other pathways combined at roughly 11%. Neste, the world’s largest renewable fuels producer, operates approximately 600,000 tonnes per year of SAF capacity — all HEFA. But commercial maturity does not mean infinite scalability. As the ICCT stated in its 2023 SAF Grand Challenge analysis: “HEFA production is projected to level off and be surpassed by second generation cellulosic SAF” by the end of the decade. That projection assumed next-generation pathways would scale on schedule. They have not.

The Feedstock Numbers That Define the Ceiling

HEFA’s cost structure explains its vulnerability. Feedstock accounts for 60–70% of HEFA facility operating costs — a ratio that makes the pathway acutely sensitive to both supply volume and price. And the supply of sustainable lipid feedstocks has hard physical limits.

Used cooking oil is the single largest HEFA feedstock. Global generation is estimated at 15–20 million tonnes per year, but the sustainable, certification-compliant portion — the share that meets RED III or CORSIA eligibility — is far smaller. Conservative estimates put today’s verified sustainable UCO supply at 1.0–1.5 million tonnes per year, with an optimistic 2030 projection of approximately 2.0 million tonnes. Europe imports 95% of its UCO, drawing primarily from Malaysia, Indonesia, and China — supply chains documented for opacity and fraud risk.

Animal fats — tallow from beef rendering, white grease, distillers corn oil, and poultry fat — add approximately 0.8–1.2 million tonnes per year of sustainable supply, growing to perhaps 1.5 million tonnes by 2030. This is a byproduct of the livestock industry; growth is tied to global meat consumption, not SAF investment.

The combined sustainable feedstock ceiling for HEFA is therefore approximately 3.5–4.0 million tonnes per year under conservative assumptions, or 4.5–5.0 million tonnes under optimistic scenarios. That ceiling does not account for competing demand. Renewable diesel absorbs approximately 60% of available UCO and animal fat supply. SAF takes roughly 25%. The IEA projects total demand for vegetable oil, waste oils, and residue fats will increase 56% by 2035, driven primarily by renewable diesel growth. HEFA SAF is not competing for a growing pie; it is fighting for a fixed slice that other sectors are also claiming.

The feedstock ceiling is not theoretical — it is arithmetic. Global sustainable lipid supply tops out at 4–5 million tonnes per year. SAF demand by 2030 requires 6–8 million tonnes. No amount of refining capacity closes a gap that starts in the field and the fryer.

The Supply-Demand Gap Is Already Opening

SAF demand under current mandates is accelerating faster than feedstock supply can follow. The EU’s ReFuelEU regulation requires 2% SAF blending by 2025 and 6% by 2030 — approximately 1.0–1.2 million tonnes rising to 3.5–4.0 million tonnes from Europe alone. The US SAF Grand Challenge targets approximately 7.5 million tonnes by 2030, though realistic US output is closer to 2.0–2.5 million tonnes. Conservative 2030 global demand runs to 6–8 million tonnes.

Against a HEFA ceiling of 4–5 million tonnes, the shortfall is 2–4 million tonnes — a 30–50% deficit. EASA’s February 2025 assessment flagged Europe’s supply shortfall directly: the continent faces a real risk of failing to deliver both the 2% 2025 target and the 6% 2030 target without major non-HEFA investment.

Sustainability Rules Are Tightening the Ceiling Further

The EU’s RED III directive, effective from 2025, raises the minimum GHG reduction threshold for SAF from 50% to 70% versus the fossil baseline. It completely prohibits food and feed crops as SAF feedstock — eliminating virgin vegetable oils from eligibility. The effect is to force total HEFA reliance on waste and residue streams — precisely the feedstocks with the hardest supply ceiling.

The UCO fraud crisis compounds the problem. Transport & Environment and multiple investigative reports have documented ongoing mislabelling of virgin palm oil as used cooking oil in Asian-to-European supply chains. Verification relies on paperwork audits, not laboratory testing. Every tonne of fraudulently labelled UCO means the real sustainable supply ceiling is lower than published estimates suggest.

The UK has taken the most explicit regulatory position. Its SAF mandate caps HEFA at 92% of SAF volumes from 2027, declining to 35% by 2040 — an explicit acknowledgement that pathway diversification is not optional.

The Next-Gen Feedstocks: What Could Replace UCO

Alcohol-to-jet (ATJ) is the nearest-term alternative. LanzaJet and Gevo are leading commercial development, with ATJ producing approximately 0.2–0.3 million tonnes today and the US DOE projecting 0.8–1.2 million tonnes by 2030. ATJ’s advantage is feedstock abundance: global ethanol production exceeds 120 billion gallons per year. ATJ plants also build faster than HEFA — 2–3 years versus 3–4.

Fischer-Tropsch gasification converts biomass, forestry residues, agricultural waste, or MSW into SAF. The ICCT estimates the EU alone has 76.5 million tonnes of agricultural residues and 21.2 million tonnes of MSW potentially available by 2030. But FT is capital-intensive and complex. Realistic 2030 production: 0.1–0.3 million tonnes. Fulcrum BioEnergy’s 2024 bankruptcy is a cautionary signal on project execution risk.

Cover crops — camelina, carinata, and pennycress — offer feedstock without competing with food production. Oil yields run 0.32–0.42 tonnes per hectare (versus 3.72–3.92 for palm oil). Realistic 2030 contribution: 0.1–0.2 million tonnes.

Power-to-liquid bypasses lipid feedstocks entirely. PtL’s scaling challenge is well documented: production cost sits at €7,695 per tonne, no commercial plants are operational, and the pathway requires renewable electricity below $30 per MWh. Swiss startups like Metafuels and Synhelion are reaching pilot milestones, but commercial materiality is a 2035+ story.

Algae remains research-phase. No commercial SAF production exists from algae; cost estimates run $10–15 per litre. Contribution by 2030: zero.

What the Feedstock Ceiling Means for SAF Targets

By 2030, maximum achievable SAF supply looks approximately like this: HEFA at 3.8–4.9 million tonnes, ATJ at 0.8–1.2 million tonnes, FT at 0.1–0.3 million tonnes, cover crops at 0.1–0.2 million tonnes, PtL below 0.1 million tonnes. Total: roughly 5–6.5 million tonnes. Against 6–8 million tonnes of demand, the shortfall is 0.5–3 million tonnes.

For Europe specifically, the ReFuelEU 6% 2030 target requires approximately 3.5–4.0 million tonnes of SAF. European HEFA feedstock supply may deliver 1.5–2.0 million tonnes. The remainder must come from ATJ, FT, or imports. The gap is not speculative; it is arithmetic.

Key Takeaways

• HEFA’s feedstock has a hard physical ceiling. Sustainable UCO supply caps at approximately 2 million tonnes per year globally; combined with animal fats, total sustainable lipid feedstock reaches 4–5 million tonnes. That is the maximum HEFA SAF the world can produce, regardless of refining capacity or capital investment.
• Renewable diesel is competing for every tonne. Approximately 60% of available UCO and animal fat supply flows to renewable diesel. The IEA projects total demand for these feedstocks to rise 56% by 2035. HEFA SAF is not just supply-constrained; it is losing a bidding war.
• Next-generation pathways are 3–5 years behind the timeline targets assume. ATJ is the closest to scale at 0.8–1.2 million tonnes projected for 2030. FT, cover crops, and PtL collectively add less than 0.5 million tonnes by the same date. Algae contributes nothing before 2050.
• The 2030 supply-demand gap is 2–4 million tonnes. Current mandates require 6–8 million tonnes of SAF globally by 2030. Achievable supply is 5–6.5 million tonnes under optimistic scenarios. Europe faces the sharpest shortfall.
• The feedstock ceiling forces a policy choice between ambition and integrity. Regulators can relax sustainability rules, accelerate capital to non-HEFA pathways, delay mandates, or accept non-compliance. All four options carry real costs. The one option not available is pretending the ceiling does not exist.