What ICAO and CORSIA actually approve

The International Civil Aviation Organization’s Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) does not certify SAF directly — it publishes default life-cycle emission values for a defined set of production routes, each separately approved under fuel-industry standard ASTM D7566. Four families cover almost everything commercially relevant today: HEFA (Hydroprocessed Esters and Fatty Acids, Annex A2, made from fats, oils and used cooking oil), FT (Fischer-Tropsch, Annex A1, built from syngas — either biomass-derived or, in the power-to-liquid variant, from captured CO₂ and hydrogen), ATJ (Alcohol-to-Jet, Annex A5, built from ethanol or isobutanol), and SIP (Synthesized Iso-Paraffins, from fermented sugars). Emissions performance varies sharply across them: Fischer-Tropsch pathways report the steepest reduction against fossil jet fuel (86–104%), followed by hydrothermal liquefaction (77–80%), with sugarcane- or corn-stover-based ATJ trailing at 60–75% — still a large cut, just not in FT’s range.

What none of the promotional material around SAF emphasises is that every one of these routes consumes hydrogen — not as an incidental input, but as a specific, chemically necessary step. The difference between pathways is not whether hydrogen is needed, but how much, and that turns out to be the single biggest lever on what a litre of SAF actually costs.

The flow scheme: where hydrogen actually enters each pathway

Laid out step by step, per ICAO’s own SAF-conversion-process documentation and the relevant ASTM D7566 annexes, the three routes relevant to India look like this:

That structural difference is the whole story. HEFA and ATJ are upgrading processes — they start with a carbon-and-hydrogen-rich feedstock (fat, oil, or alcohol) that already looks roughly like a fuel, and use hydrogen to clean it up and stabilise it. FT/power-to-liquid is a construction process — it builds the hydrocarbon chain from scratch out of CO₂ and hydrogen, so hydrogen isn’t a finishing touch, it’s the primary feedstock.

Quantifying it: grams of hydrogen per litre of SAF

India-specific figures, laid out in a 2026 analysis by the sustainability advisory Xynteo on hydrogen’s role in India’s SAF roadmap, put HEFA and ATJ at roughly 50 kilograms of hydrogen per tonne of finished SAF, and power-to-liquid at roughly 660 kilograms per tonne — more than thirteen times as much. Converting at SAF’s typical density (~0.8 kg per litre), that works out to roughly 40 grams of hydrogen per litre for HEFA/ATJ against roughly 500–530 grams per litre for PtL.

The ATJ figure is the weaker of the three: the Xynteo source groups it with HEFA at the same ~50 kg/tonne order of magnitude rather than publishing a separately derived ATJ-specific number, and separate technical literature on ATJ describes the hydrogen-balance approach differently — some integrated ATJ refinery designs reach hydrogen self-sufficiency by reforming a small share (on the order of 5%) of the incoming ethanol itself, rather than sourcing external hydrogen at all. Both descriptions are consistent with ATJ needing much less hydrogen than PtL; neither pins the ATJ number down as precisely as the HEFA and PtL figures are pinned down here.

Why PPAC and MoPNG are specifically backing the alcohol-to-jet route

India’s Ministry of Petroleum and Natural Gas, together with the Ministry of Civil Aviation and the DGCA, has cleared a specific regulatory framework allowing ethanol blending into aviation turbine fuel via the Alcohol-to-Jet pathway, ahead of the 1% SAF mandate on select international routes from 2027. The logic is straightforward: India already runs a large, government-supported ethanol-blending programme for petrol (the EBP programme, covered elsewhere on this blog), and periodically produces more sugarcane- and grain-based ethanol than that programme alone can absorb. ATJ gives that surplus ethanol capacity a second, higher-value market, without requiring India to import feedstock (as HEFA increasingly does, once domestic used-cooking-oil supply is exhausted) or to build an entirely new hydrogen-and-carbon-capture supply chain (as PtL would).

The technology readiness signal is real and recent: Petroleum and Natural Gas Minister Hardeep Singh Puri inaugurated an integrated SAF demonstration plant (built by Praj Industries under licence from Axens’ Jetanol™ ATJ technology) that has now validated both ATJ feedstock routes — bio-isobutanol first, and bio-ethanol subsequently — making Praj, on the available reporting, the first company globally to demonstrate a fully integrated end-to-end ATJ process on both feedstocks. Separately, Indian Oil Corporation is reported to be building a dedicated ATJ-SAF unit at its Panipat refinery, using LanzaJet’s alcohol-to-jet technology on an ethanol feedstock, targeted for commissioning in 2027-28.

The demand curve: India’s SAF mandate in crore litres, and the hydrogen behind it

India’s SAF blending targets are indicative, not yet fully locked into a binding schedule, but the numbers most consistently reported are 1% by 2027, 2% by 2028, and 5% by 2030, applying first to international and later potentially to domestic routes. Against an assumed Air Turbine Fuel (ATF) consumption baseline of roughly 16 million tonnes by 2030, Xynteo’s analysis puts the 2027 1% target at roughly 140 million litres (14 crore litres, ~112 kilotonnes) of SAF, and the 2030 5% target at roughly 800 kilotonnes, which converts to roughly 100 crore litres at SAF’s typical density.

The spread between the two hydrogen-demand scenarios is the actual finding here: meeting the 2030 target through HEFA/ATJ-heavy supply would need on the order of 40 kilotonnes of green hydrogen a year; meeting the same target through a PtL-heavy supply mix would need roughly 528 kilotonnes — more than thirteen times as much, for the exact same volume of fuel and the exact same blending mandate. In practice, the realistic near-term mix is overwhelmingly HEFA (IOCL’s UCO-based Panipat capacity) with ATJ arriving from 2027-28, so the SAF mandate’s actual near-term draw on India’s green-hydrogen supply is closer to the lower end of that range — it only climbs toward the higher end if and when PtL capacity is actually built at scale, which as of this writing exists in India only as an MoU-stage exploration (NTPC Green Energy and Honeywell UOP, on captured CO₂ and hydrogen feedstock) rather than committed capacity.

The price trajectory: why green hydrogen's cost curve is the SAF blending mandate's real constraint

This blog has already tracked India’s actual green-hydrogen cost curve in detail: recent SIGHT-scheme tenders cleared at $4.11–4.21 per kilogram (₹387–397), against the National Green Hydrogen Mission’s own $1.50/kg by 2030 target, with roughly $2–2.50/kg cited elsewhere as the more realistic global threshold for commercial viability (see this blog’s piece on the levelised cost of hydrogen for the full breakdown). SAF pricing sits directly downstream of that curve. At today’s roughly $4–5/kg hydrogen cost, Xynteo’s analysis puts power-to-liquid SAF at $8–10 a litre — several multiples above HEFA SAF, which the trade press currently prices around $1,800 a tonne globally (roughly $1.45/litre), itself already a 2–5× premium over conventional jet fuel depending on route and period.

There is a partial escape route already visible in India-specific modelling: a hybrid Power-and-Biomass-to-Liquid (PBtL) pathway, which tops up biomass-derived syngas (from agricultural residue) with green hydrogen rather than building the entire carbon backbone from captured CO₂, has been costed by the Berkeley-based India Energy & Climate Center at roughly $1.41 a litre assuming a $3/kg hydrogen price — already close to the SIGHT-tender range cited above, and dramatically cheaper than pure PtL because it needs far less green hydrogen per litre of output. Whether PBtL, ATJ, or HEFA ends up carrying most of India’s SAF volume as the mandate tightens toward 2030 is still an open question, but the direction of the argument holds regardless of which one wins: hydrogen-intensive SAF only becomes affordable at the volumes the mandate implies once green hydrogen itself gets close to its $1.50–2.50/kg target range — the SAF blending curve and the hydrogen price curve are not two separate policy stories, they are the same story, priced in two different units.

Sources and caveats