For years, Sustainable Aviation Fuel (SAF) has been pitched as the saviour of air travel’s climate footprint. Politicians point to it, airlines market it and investors circle it. But scratch the surface and the maths, physics and logistics tell a different story - SAF will never scale to the percentages that really matter - never ever.
Aviation burns approximately 350 million tonnes of jet fuel every year. To make 30% of that SAF would mean producing somewhere between 100 - 110 million tonnes annually. Putting that in perspective, today, SAF contributes less than 1% of jet fuel demand.
HEFA (Hydroprocessed Esters and Fatty Acids) made from used cooking oil, tallow and vegetable oils is today’s dominant SAF pathway. It’s by far the easiest to commercialise but utterly capped by feedstock. Jet cut from HEFA equates to approximately 15 - 35% of product, so to supply 30% SAF, we’d need 300 - 700 million tonnes of waste lipids every year.
When you run HEFA through a refinery process, you don’t get 100% jet fuel out the other end. You get a slate of products including renewable diesel (HVO) (the majority product) naphtha (lighter hydrocarbons). Jet fuel range (SAF) is only a slice of the barrel, so if you put in 100 tonnes of used cooking oil, you might get 15 - 25 tonnes jet fuel (the “jet cut”). For this reason, HEFA is a side-stream supplier of SAF, not a dominant source. Even if you maxed out all global used cooking oil and fats, most of it comes out as road diesel, not jet.
Global used cooking oil supply is currently around 30 million tonnes. Add in animal fats and you still miss the target by a factor of 10.
Another source of SAF is the gasification/Fischer Tropsch route which promises jet fuel from crop residues, forestry offcuts and municipal waste. On paper it works (in practice) although the yield is around 0.1 tonne jet per tonne of dry biomass, so to hit 30% SAF you'd need around 1 billion tonnes of biomass every year; biomass that's also needed in power generation, heating, soil health and has multiple material uses.
Even if technically viable, mobilising and processing that volume sustainably is closer to fantasy than policy.
Lastly, there's the Power-to-Liquid (PtL) and the energy maths bites hard; SAF needs 23–28 kWh per litre of jet so a meaningful 30% SAF (120–130 billion litres) would need approximately 2,700 - 3,500 TWh per year which equates to about 10% of total global electricity generation in 2023.
In addition, there's the 400 million tonnes of CO₂ (estimated) to be captured and processed which ultimately means that building that scale of renewables, electrolysers, CO₂ capture and PtL plants is not a policy ambition, it’s a civilisational undertaking.
Even the EU’s bold ReFuelEU regulation only mandates 6% SAF by 2030. Current build-outs globally don’t get close to double digits. 30% is not on the map. Not in the 2030s, not in the 2040s. More like this (flying) - link - more like this (SAF) - link
HEFA (Hydroprocessed Esters and Fatty Acids) made from used cooking oil, tallow and vegetable oils is today’s dominant SAF pathway. It’s by far the easiest to commercialise but utterly capped by feedstock. Jet cut from HEFA equates to approximately 15 - 35% of product, so to supply 30% SAF, we’d need 300 - 700 million tonnes of waste lipids every year.
When you run HEFA through a refinery process, you don’t get 100% jet fuel out the other end. You get a slate of products including renewable diesel (HVO) (the majority product) naphtha (lighter hydrocarbons). Jet fuel range (SAF) is only a slice of the barrel, so if you put in 100 tonnes of used cooking oil, you might get 15 - 25 tonnes jet fuel (the “jet cut”). For this reason, HEFA is a side-stream supplier of SAF, not a dominant source. Even if you maxed out all global used cooking oil and fats, most of it comes out as road diesel, not jet.
Global used cooking oil supply is currently around 30 million tonnes. Add in animal fats and you still miss the target by a factor of 10.
Another source of SAF is the gasification/Fischer Tropsch route which promises jet fuel from crop residues, forestry offcuts and municipal waste. On paper it works (in practice) although the yield is around 0.1 tonne jet per tonne of dry biomass, so to hit 30% SAF you'd need around 1 billion tonnes of biomass every year; biomass that's also needed in power generation, heating, soil health and has multiple material uses.
Even if technically viable, mobilising and processing that volume sustainably is closer to fantasy than policy.
Lastly, there's the Power-to-Liquid (PtL) and the energy maths bites hard; SAF needs 23–28 kWh per litre of jet so a meaningful 30% SAF (120–130 billion litres) would need approximately 2,700 - 3,500 TWh per year which equates to about 10% of total global electricity generation in 2023.
In addition, there's the 400 million tonnes of CO₂ (estimated) to be captured and processed which ultimately means that building that scale of renewables, electrolysers, CO₂ capture and PtL plants is not a policy ambition, it’s a civilisational undertaking.
Even the EU’s bold ReFuelEU regulation only mandates 6% SAF by 2030. Current build-outs globally don’t get close to double digits. 30% is not on the map. Not in the 2030s, not in the 2040s. More like this (flying) - link - more like this (SAF) - link
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