The International Air Transport Association estimated that global aviation sector corresponds to 900 million tons of CO2 annually and accounts for 2.5% of CO2 emissions. The aviation industry has set the target to achieve net zero emissions by 2050. Sustainable Aviation fuel (SAF) is estimated to be the solution to decarbonize the aviation industry.
Sustainable aviation fuel is used to power aircraft. It is basically a biofuel and exhibits properties similar to jet fuel. Depending on the feedstock used to produce it, these fuels can either reduce the emission of greenhouse gases or have a net negative greenhouse gas footprint. As per US Environmental Protection Agency, aviation greenhouse gases accounts for 9-12% of US’s transportation greenhouse gas emissions. The feedstock for Sustainable Aviation fuel (SAF) could be corn grain, oil seeds, algae, agricultural, and forestry residue, wood mill waste, municipal solid waste, fats, oils, greases etc. Currently, Sustainable Aviation fuel (SAF) is produced through 8 certified technologies for its commercial use in the aviation industry.
Fischer Tropsch Technology: In this technology, synthetic gas is converted into Sustainable Aviation fuel (SAF) and other fuels through FT synthesis. ASTM has certified two different FT processes to produce Fischer Tropsch straight paraffinic kerosene jet fuel (FT-SPK) and Fischer Tropsch Straight paraffinic kerosene with aromatic compound (FT-SAK/A). FT-SPK is produced from forestry waste, grasses and MSW and it was approved in 2009. Whereas FT-SPK is produced from agricultural, forestry waste, wood and energy crops, MSW and the technology was approved in 2015. Currently both biofuels are blended up to 50%.
Hydrotreated Esters and Fatty Acids (HEFA): HEFA was approved in 2011. The feedstock used are vegetable oils, waste oils, fats. Firstly, Oxygen is removed from the feedstock through hydrodeoxygenation and then the straight chain paraffinic molecules are cracked and isomerised into jet fuel. Sustainable Aviation fuel (SAF) produced from HEFA process is used with 50% blend.
Synthesized Iso-Paraffins (SIP): SIP is produced by microbial conversion of C6 sugars into farnesene, which are converted into Sustainable Aviation fuel (SAF) after hydrogen treatment. This pathway is used by Amyris with up to 10% blend after it was approved in 2014.
Alcohol to Jet Synthetic Paraffinic Kerosene (ATJ-SPK): Sustainable Aviation fuel (SAF) is produced from alcohol by removing oxygen from alcohol and then through oligomerisation process. Use of ethanol and iso-butanol is approved for ATJ technology. The source of alcohols could be agricultural waste products. ATJ technology with iso-butanol was approved in 2016 with 30% blend and currently GEVO uses it. ATJ technology with ethanol is used by ARA and Euglena and its was approved in 2018 for 50% blend.
Catalytic Hydrothermolysis Synthetic Jet Fuel (CHJ): The feedstock for this process is plant oils, waste oils, soyabean oil, jatropha oil, algal oil etc. Fatty acids from these feedstocks is subjected to catalytic hydrothermolysis followed by hydrotreatment, hydrocracking and fractionation to produce Sustainable Aviation fuel (SAF).CHJ technology was approved in 2020 and ARA and Euglena are currently using it 50% blend.
High Hydrogen Content Synthetic Paraffinic Kerosene (HHC-SPK): Biologically derived hydrocarbon such as algae and fatty acids esters are hydro-processed for saturation and for removal of oxygen to produce Sustainable Aviation fuel (SAF). Technology was approved in 2020 and can be used with 10% blend.
Producing Sustainable Aviation fuel (SAF) has some benefits such as it brings new opportunities for farming communities, improving environment as well as boosts the performance of aircrafts. Farmers can earn more revenue during off seasons by growing and providing biomass crops to the Sustainable Aviation fuel (SAF) market. There are some major benefits on environment due to Sustainable Aviation fuel (SAF), if biofuels are produced from manure, sewage sludge and other wet waste then it keeps out methane gas from environment and reduces pollution on watersheds. Sustainable Aviation fuel (SAF) enables comparatively cleaner air surrounding the airport. Since Sustainable Aviation fuel (SAF) is composed of less aromatic components, they are clean burning fuel and hence reduces the emission of harmful gases surrounding the airport during take-off and landing.
US aviation company, Southwest Airlines has collaborated with National Energy Renewable Laboratory of USA on wet waste flight demonstration project in 2019 to make Sustainable Aviation fuel (SAF) commercially viable for aircrafts. Under this project, Sustainable Aviation fuel (SAF) will consist of combination of renewable iso-paraffins and straight chain paraffins and will be blended with up to 70% concentration in conventional jet fuel.
There are many other developments going on regarding the use of Sustainable Aviation fuel (SAF) in aircrafts. Airbus’ A321neo took with its both engines powered by Sustainable Aviation fuel (SAF) which is 100% unblended from Toulouse, France in March 2023. A321neo is the first Airbus single Aisle aircraft to run on 100% Sustainable Aviation fuel (SAF) (bio jet fuel). Currently, the commercial and military aircrafts and helicopters of Airbus are certified to fly up with 50% blend of Sustainable Aviation fuel (SAF). Airbus will evaluate the emissions of unblended Sustainable Aviation fuel (SAF) through the A321neo to achieve its goal of using 100% Sustainable Aviation fuel (SAF) by 2030.
Indian aviation industry is also taking initiatives for development in Sustainable Aviation fuel (SAF). On March 2022, Spice JET, Boeing and CSIR, (Indian Institute of Petroleum) announced to explore the opportunities for Sustainable Aviation fuel (SAF) in the Indian aviation industry. CSIR will supply Sustainable Aviation fuel (SAF) to Spice jet to decarbonise its aviation fleet. GMR group is also partnering with French companies, Safran, Axens and Airbus for the development of Sustainable Aviation fuel (SAF) based on agricultural products. A memorandum of understanding was signed at Wings, India in March 2022.
As per news released by PRNewswire in March 2023, Boeing has agreed to buy more than double the quantity of Sustainable Aviation fuel (SAF) from last year. Boeing will purchase 5.6 Million gallons of Sustainable Aviation fuel (SAF) produced by Neste (the world’s leading producer of SAF, renewable diesel, and renewable feedstock, headquartered in Finland) for its commercial operations in the USA for 2023. Neste will provide Neste My Sustainable Aviation fuel blended with 30% blend produced from renewable waste.
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