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SAF Sustainable Aviation Fuel

January 11, 2021
Harold Goodwin
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As the Economist cautioned back in November 2018
"A report by America’s National Academy of Sciences says that even the cheapest negative-emissions technologies such as biomass with carbon capture and storage are still too limited in scale to make a big dent in atmospheric CO2. A study by Britain’s Royal Society and Royal Academy of Engineering said a carbon price of $100 a tonne may be needed to make most negative-emissions projects feasible. The danger is that policymakers will delay curbing emissions now in the hope of being able to remove large amounts of greenhouse gases from the air in the future. In fact, both are needed on a massive scale."

When burned SAF produces the same amount of CO2 emissions as conventional jet fuel. SAF is preferred because its production process absorbs CO2, leading to a reduction in CO2 emissions of 70 to 100 per cent on a life-cycle basis.

SAF has the advantage of being a drop-in fuel, compatible with fuelling infrastructure and engines.

The technical feasibility of SAF from vegetable or waste oils is now proven, the product is certified, and some airlines use the fuel regularly as part of the mix ion the tanks. The feedstock, supply chain and the production and refining are costly. The biggest problem is the competition for land use - “food versus fuel”. Cathay Pacific and United Airlines have invested in producing fuel frim household waste and the fermentation of wood waste is a possibility. 


  • Used cooking oil and other non-palm waste oils from animals or plants.
  • Other sources including forestry waste (such as waste wood), energy crops (fast growing plants) and algae.

Biofuels Digest 

Solid waste from homes and businesses, such as packaging, paper, textiles, and food scraps that would otherwise go to landfill or incineration.

Synfuels: power-to-liquid fuels (PtL)
The use of synfuels derived from hydrogen and captured carbon emissions could become a scalable option. Such synfuels require water, renewable electricity to produce hydrogen, and CO2. The efficacy of synfuels to reduce greenhouse gas emissions requires that the Hydrogen is produced using green electricity and the CO2 needs to be extracted from the carbon cycle (taken from the air with direct air capture). McKinsey's analysis suggests that while current SAF costs are high in relation to kerosene cost, they will come down over time and could reach breakeven between 2030 and 2035, in an optimistic scenario. more

PtL uses renewable electricity, carbon dioxide captured from air and water to form a sustainable fuel that chemically resembles conventional jet fuel. Despite more R&D work being required and high implementation cost, PtL has advantages over other SAFs. It is “drop-in” capable, uses renewable feedstock and does not require as much land compared to other types of SAF.

Canadian SAF+ Consortium 

Direct Air Capture
Direct Air Capture can be used to pump CO2 underground and store it permanently underground. It is also possible that captured CO2 can be used to create aviation fuel.

June 2o20 the International Energy Agency reviewed progress on DAC.
The CO2 can be permanently stored in deep geological formations or used in the production of fuels, chemicals, building materials and other products containing CO2. When CO2 is geologically stored, it is permanently removed from the atmosphere, resulting in negative emissions. There are currently 15 direct air capture plants operating worldwide, capturing more than 9 000 tCO2/year, with a 1 MtCO2/year capture plant in advanced development in the United States. In the SDS, direct air capture is scaled up to capture almost 10 MtCO2/year by 2030. This is within reach but will require several more large-scale demonstrations to refine the technology and reduce capture costs. more

Dec 10, 2020 United Airlines announced that they plan to be 100% green by reducing its greenhouse gas (GHG) emissions by 100% by 2050. They plan to advance towards carbon neutrality by committing to a multimillion-dollar investment in revolutionary atmospheric carbon capture technology known as Direct Air Capture. Scott Kirby, United's chief executive officer. said "These game-changing technologies will significantly reduce our emissions, and measurably reduce the speed of climate change – because buying carbon offsets alone is just not enough. Perhaps most importantly, we're not just doing it to meet our own sustainability goal; we're doing it to drive the positive change our entire industry requires so that every airline can eventually join us and do the same." Rather than simply taking a conventional approach to decarbonization by relying solely on the purchase of carbon offsets, United intends to make a multimillion-dollar investment in 1PointFive, Inc., a partnership between Oxy Low Carbon Ventures, a subsidiary of Occidental (NYSE:OXY), and Rusheen Capital Management. 1PointFive's mission is to curb the rise in global temperatures by physically removing carbon dioxide (CO2) from the air using Direct Air Capture technology licensed from Carbon Engineering. more

Battery Powered 

Heart Aerospace’s first electric airliner to be operational by 2026.  all-electric aircraft ES-19 will sport a range of 400km with 215 knots of top speed. The airliner is also claimed to be capable of operating from shorter runways that are just 750 meters long. The new electric drivetrain, coupled with the new battery technology, will be able to push the aircraft to achieve a reasonable range, claims the company. They claim "Electrification changes the equation for regional air travel. Electric aircraft are affordable to buy, operate and maintain. Simple, reliable electric motors reduce maintenance costs by 90% compared to turboprops, and intelligent electronic monitoring reduces inspection needs. Most importantly, fuel costs go down by 50-75%."

Israeli firm Eviation has developed  Alicewhich they say will carry nine passengers for up to 650 miles (1,040km) at 10,000ft (3,000m) at 276mph (440km/h). It is expected to enter service in 2022. It is powered by three rear-facing pusher-propellers, one in the tail and two counter-rotating props at the wingtips to counter the effects of drag. It also has a flat lower fuselage to aid lift. Eviation has already received its first orders. US regional airline Cape Air, which operates a fleet of 90 aircraft, has agreed to buy a "double-digit" number of the aircraft. source

In 2017 Airbus, Rolls-Royce and Siemens teamed up to develop a hybrid-electric engine plane technology as part of a push towards cleaner aviation. In the E-Fan X programme, they planned to put an electric engine with three jet engines on a BAe 146 aircraft. This was abandoned in 2020



A Guide to Sustainable Aviation Fuels

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