Aviation biofuel

An aviation biofuel or bio-jet fuel[1] or bio-aviation fuel (BAF)[2] is a biofuel used to power aircraft and is said to be a sustainable aviation fuel (SAF). The International Air Transport Association (IATA) considers it a key element to reducing the carbon footprint within the environmental impact of aviation.[3] Aviation biofuel could help decarbonize medium- and long-haul air travel generating most emissions, and could extend the life of older aircraft types by lowering their carbon footprint.

Refueling an Airbus A320 with biofuel in 2011

Biofuels are biomass-derived fuels from plants or waste; depending on which type of biomass is used, they could lower CO2 emissions by 20–98% compared to conventional jet fuel.[4] The first test flight using blended biofuel was in 2008, and in 2011 blended fuels with 50% biofuels were allowed in commercial flights. In 2019, the IATA was aiming for a 2% penetration by 2025.

Aviation biofuel can be produced from plant sources such as Jatropha, algae, tallows, waste oils, palm oil, Babassu, and Camelina (bio-SPK); from solid biomass using pyrolysis processed with a Fischer–Tropsch process (FT-SPK); with an alcohol-to-jet (ATJ) process from waste fermentation; or from synthetic biology through a solar reactor. Small piston engines can be modified to burn ethanol.

Sustainable biofuels do not compete with food crops, prime agricultural land, natural forest or fresh water. They are an alternative to electrofuels.[5] Sustainable aviation fuel is certified as being sustainable by a third-party organisation.

Environmental impact
Further information: Environmental impact of aviation and Biofuel § Greenhouse gas emissions

Plants absorb carbon dioxide as they grow, meaning plant-based biofuels emit only the same amount of greenhouse gases as previously absorbed. Biofuel production, processing and transport however emit greenhouse gases, reducing the emissions savings.[2] Biofuels with most emission savings are those derived from photosynthetic algae (98% savings, technology not yet mature) and from non-food crops and forest residues (91–95% savings).[2]

Jatropha oil, a non-food oil used as a biofuel, should lower CO2 emissions by 50–80% compared to Jet-A1.[6] Jatropha, used for biodiesel, can thrive on marginal land where most plants would produce low crop yields.[7][8] A life cycle assessment by the Yale School of Forestry on jatropha, one source of potential biofuels, estimated that using it could reduce greenhouse gas emissions by up to 85% if former agro-pastoral land is used, or increase emissions by up to 60% if natural woodland is converted to use.[9]

Palm oil cultivation is constrained by scarce land resources and its expansion to forestland causes deforestation and biodiversity loss, and direct and indirect emissions due to land-use change.[2] Neste Corporation's renewable products include a refining residue of food-grade palm oil, the oily waste skimmed from the palm oil mill's wastewater. Other Neste sources are UCO (used cooking oil) from deep fryers and animal fats.[10] Neste's sustainable aviation fuel is used by Lufthansa;[11] Air France and KLM announced 2030 SAF targets[12] and announced multi-year purchase contracts totalling over 2.4 million tonnes of SAF from Neste, TotalEnergies and DG Fuels.[13]

NASA has determined that 50% aviation biofuel mixture can cut particulate emissions caused by air traffic by 50–70%.[14] Biofuels do not contain sulfur compounds and thus do not emit sulfur dioxide.

Timeline
See also: Aviation biofuel demonstrations

The first flight using blended biofuel took place in 2008.[15] Virgin Atlantic flew the first flight by a commercial airline to be powered partly by biofuel, while commercial biofuel flights were likely to use feedstocks such as algae.[16] By then, airlines representing more than 15% of the industry formed the Sustainable Aviation Fuel Users Group, with support from NGOs such as Natural Resources Defense Council and The Roundtable For Sustainable Biofuels. They pledged to develop sustainable biofuels for aviation.[17] That year, Boeing was co-chair of the Algal Biomass Organization, joined by air carriers and biofuel technology developer UOP LLC (Honeywell).[18]

In 2009, the IATA committed to achieve carbon-neutral growth by 2020, and to halve carbon emissions by 2050.[19]

In 2010, Boeing targeted of 1% of global aviation fuels by 2015.[20]

US Marine Corps AV-8B Harrier II test flight using a 50–50 biofuel blend in 2011

By June 2011, the revised Specification for Aviation Turbine Fuel Containing Synthesized Hydrocarbons (ASTM D7566) allowed commercial airlines to blend up to 50% biofuels with conventional jet fuel.[21] The safety and performance of jet fuel used in passenger flights is certified by ASTM International.[22] Biofuels were approved for commercial use after a multi-year technical review from aircraft makers, engine manufacturers and oil companies.[23] Since then, some airlines have experimented with using biofuels on commercial flights.[24] As of July 2020, there have been published seven annexes to D7566, including as much types of biofuels: Fischer-Tropsch Synthetic Paraffinic Kerosene (FT-SPK, 2009), Hydroprocessed Esters and Fatty Acids Synthetic Paraffinic Kerosene (HEFA-SPK, 2011), Hydroprocessed Fermented Sugars to Synthetic Isoparaffins (HFS-SIP, 2014), Fischer-Tropsch Synthetic Paraffinic Kerosene with Aromatics (FT-SPK/A, 2015), Alcohol to Jet Synthetic Paraffinic Kerosene (ATJ-SPK, 2016), Catalytic Hydrothermolysis Synthesized Kerosene (CH-SK, or CHJ; 2020).[25]

In December 2011, the FAA awarded US$7.7 million to eight companies to develop drop-in sustainable fuels, especially from alcohols, sugars, biomass, and organic matter such as pyrolysis oils, within its CAAFI and CLEEN programs.[26]

From 2014, Solena planned to turn annually 500,000 tonnes of waste from the City of London that would normally go to landfill into biofuel to be used in the British Airways fleet,[27] but filed for bankruptcy in 2015.[28]

By 2015, cultivation of fatty acid methyl esters and alkenones from the algae, Isochrysis, was under research as a possible jet biofuel feedstock.[29]

By 2016, Thomas Brueck of Munich TU was forecasting that algaculture could provide 3–5% of jetfuel needs by 2050.[30]

In Fall 2016, to achieve its emissions reductions goals, the ICAO planned multiple measures including the development and deployment of sustainable aviation fuels.[31]

Dozens of companies received hundreds of millions in venture capital from 2005 to 2012 to extract fuel oil from algae, some promising competitively priced fuel by 2012 and a production of 1 billion US gal (3.8 million m3) by 2012-2014.[32] By 2017, nor were achieved and most companies had disappeared or changed their business plans to focus on cosmetics supplements, nutraceuticals, pet food additives, animal feed, pigments and speciality oils.[32]

In 2019, 0.1% of fuel was SAF:[33] the International Air Transport Association (IATA) supports the adoption of Sustainable Aviation fuel, aiming in 2019 for a 2% penetration by 2025: 7 million m3 (1.8 billion US gal).[34] By then, more than 150,000 flights have used biofuels and five airports have regular biofuel distribution: Bergen, Brisbane, Los Angeles, Oslo and Stockholm, with others offering occasional supply.[15]

In 2019, United Airlines purchased up to 10 million US gallons (38,000 m3) of SAF from World Energy over two years.[35]

That year, Virgin Australia had fueled more than 700 flights and flown more than one million kilometers, domestic and international, using Gevo's alcohol-to-jet fuel.[36] Gevo is committed to going after the entire gallon of sustainable aviation fuel, potentially leading to a negative carbon footprint. Virgin Atlantic was working to regularly use fuel derived from the waste gases of steel mills, with LanzaTech.[37] British Airways wanted to convert household waste into jet fuel with Velocys.[37] United Airlines committed to 900 million US gal (3,400,000 m3) of sustainable aviation fuel for 10 years from Fulcrum BioEnergy (to be compared to its 4.1 billion US gal (16,000,000 m3) fuel consumption in 2018), after its $30 million investment in 2015, and will develop up to five biofuel factories near its hubs.[37]

From 2020, Qantas will start using a 50/50 blend of SG Preston's biofuel on its Los Angeles-Australia flights, also providing fuel derived from non-food plant oils to JetBlue Airways during 10 years.[37] At its sites in Singapore, Rotterdam and Porvoo, Finland's Neste is expecting to improve its renewable fuel production capacity from 2.7 to 3.0 million t (6.0 to 6.6 billion lb) a year by 2020, and is increasing its Singapore capacity by 1.3 million t (2.9 billion lb) to reach 4.5 million t (9.9 billion lb) in 2022 by investing €1.4 billion ($1.6 billion).[37]

By 2020, International Airlines Group had invested $400 million to convert waste into sustainable aviation fuel with Velocys.[38]

In early 2021, Boeing's CEO Dave Calhoun said drop-in sustainable aviation fuels are "the only answer between now and 2050" to reduce carbon emissions.[39]

Production

Jet fuel is a mixture of various hydrocarbons. The range of their sizes (molecular weights or carbon numbers) is restricted by the requirements for the product, for example, freezing point or smoke point. Jet fuels are sometimes classified as kerosene or naphtha-type. Kerosene-type fuels include Jet A, Jet A-1, JP-5 and JP-8. Naphtha-type jet fuels, sometimes referred to as "wide-cut" jet fuel, include Jet B and JP-4.

"Drop-in" biofuels are biofuels that are completely interchangeable with conventional fuels. Deriving "drop-in" jet fuel from bio-based sources is ASTM approved via two routes. ASTM has also found it safe to blend in 50% SPK into regular jet fuels.[40][22] Only tests have been done so far with blending in synthetic paraffinic kerosene (SPK) in considerably higher concentrations.[41]

HEFA-SPK
Hydroprocessed Esters and Fatty Acids Synthetic Paraffinic Kerosine (HEFA-SPK) is a specific type of hydrotreated vegetable oil fuel.[2] As of 2020 this was the only mature technology.[15][2] HEFA-SPK fuel is considered to be a leading alternative replacement for conventional jet fuel by the CAA.[42] HEFA-SPK was approved by Altair Engineering for use in 2011.[43] HEFA-SPK is produced by the deoxygenation and hydroprocessing of the feedstock fatty acids of algae, jatropha, and camelina.[44]
Bio-SPK
This fuel uses oil that is extracted from plant sources such as jatropha, algae, tallows, waste oils, babassu, and Camelina to produce synthetic paraffinic kerosene (bio-SPK) by cracking and hydroprocessing. Using algae to make jet fuel remains an emerging technology. Companies working on algae jet fuel include Solazyme, Honeywell UOP, Solena, Sapphire Energy, Imperium Renewables, and Aquaflow Bionomic Corporation. Universities working on algae jet fuel are Arizona State University and Cranfield University. Major investors for algae based SPK research are Boeing, Honeywell/UOP, Air New Zealand, Continental Airlines, Japan Airlines, and General Electric.
FT-SPK
Another route involves processing solid biomass using pyrolysis to produce oil or gasification to produce a syngas that is processed into FT SPK (Fischer–Tropsch Synthetic Paraffinic Kerosene).
ATJ-SPK
Alcohol-to-jet (ATJ) pathway takes alcohols such as ethanol or butanol and de-oxygenates and processes them into jet fuels.[45] Companies such as LanzaTech have created ATJ-SPK from CO2 in flue gases.[46] The ethanol is produced from CO in the flue gases using microbes such as Clostridium autoethanogenum. In 2016 LanzaTech demonstrated its technology at Pilot scale in NZ –using Industrial waste gases from the steel industry as a feedstock for its microbial fermentation.[47][48][49] Gevo developed technology to retrofit existing ethanol plants to produce isobutanol.[50] Alcohol-to-Jet Synthetic Paraffinic Kerosene (ATJ-SPK) is a proven pathway to deliver a bio-based, low-carbon option to travelers.
Future production routes
Systems that use synthetic biology to create hydro-carbons are under development.
  • The SUN-to-LIQUID project is examining Fischer-Tropsch hydro-carbon fuels (solar kerosine) through the use of a solar reactor.[51][52][53]
  • Alder Fuels raw material is waste from forestry and agriculture. This is mainly structural polymers cellulose, hemicellulose and lignin. They are processed via pyrolysis. The result is condensed into greencrude, a hydrocarbon-rich liquid, which is turned into fuel in refineries.[54]
Piston engines
Small piston engines can be modified to burn ethanol.[55] Swift Fuel, a biofuel alternative to avgas, was approved as a test fuel by ASTM International in December 2009.[56][57]
Technical challenges
Nitrile-based rubber materials expand in the presence of aromatic compounds found in conventional petroleum fuel. Pure biofuels that aren't mixed with petroleum and don't contain paraffin-based additives may cause rubber seals and hoses to shrink.[58] Synthetic rubber substitutes that are not adversely affected by biofuels, such as Viton, for seals and hoses are available.[59] The United States Air Force found harmful bacteria and fungi in their biofueled aircraft, and use pasteurization to disinfect them.[60]

Economics

The International Energy Agency forecast SAF production should grow from 18 to 75 billion litres between 2025 and 2040, representing a share of aviation fuel getting from 5% to 19%.[15] By 2019, fossil jet fuel production cost was $0.3-0.6 per L given a $50–100 crude oil barrel, while aviation biofuel production cost was $0.7-1.6, needing a $110–260 crude oil barrel to break-even.[15]

As of 2020 aviation biofuel is more expensive than fossil jet kerosene,[1] considering aviation taxation and subsidies at that time.[61]

Sustainable aviation fuels
In 2016, Oslo Airport became the first international airport to offer sustainable aviation fuel as part of the fuel mix.

Sustainable biofuels do not use food crops, prime agricultural land or fresh water. Sustainable aviation fuel (SAF) is certified by a third-party such as the Roundtable For Sustainable Biofuels.[62]

Sustainable fuels can be created with renewable energy without biomaterial. Carbon can be sourced from CO
2 to make kerosene, etc. Hydrogen can be combusted or used in a fuel cell, although storage and transport remain challenging.

As of 2022, some 450,000 flights had used sustainable fuels as part of the fuel mix, although such fuels were ~3x more expensive than the traditional fossil kerosene.[63]

Certification

A sustainable aviation fuel (SAF) sustainability certification verifies that the product has satisfied criteria focused on environmental, social and economic "triple-bottom-line" considerations. Under many emission regulation schemes, such as the European Union Emissions Trading Scheme (EUTS), a certified SAF product may be exempted from carbon compliance liability costs.[64] This marginally improves SAF's economic competitiveness over fossil-based fuel. However, commercialisation and regulatory hurdles remain to achieve price parity and to enable widespread uptake.[65]

The first reputable body to launch a sustainable biofuel certification system was the European-based Roundtable on Sustainable Biomaterials (RSB) NGO.[66] Leading airlines and other signatories to the Sustainable Aviation Fuel Users Group (SAFUG) pledged to support RSB as the preferred certification provider.[67][68]

Criteria
EU RED II Recast (2018)
Greenhouse gas emissions from sustainable fuels must be lower than those from the fuels they replace: at least 50% for production built prior to 5 October 2015, 60% after that date and 65% after 2021. Raw materials cannot be sourced from land with high biodiversity or high carbon stocks (i.e. primary and protected forests, biodiversity-rich grasslands, wetlands and peatlands). Other sustainability issues are set out in the Governance Regulation and may be covered on a voluntary basis.
ICAO 'CORSIA'
GHG Reduction - Criterion 1: lifecycle reductions of at least 10% compared to fossil fuel. Carbon Stock - Criterion 1: not produced from biomass obtained from land whose uses changed after 1 January 2008 from primeval forests, wetlands or peatlands, as all these lands have high carbon stocks. Criterion 2: For land use changes after 1 January 2008, (using IPCC land categories), if emissions from direct land use change (DLUC) exceed the default value of the induced land use change (ILUC), the value of the DLUC replaces the default (ILUC) value.

Global impact

As emissions trading schemes and other carbon compliance regimes emerge, certain biofuels are likely to be exempted ("zero rated") by governments from carbon compliance due to their closed-loop nature, if they can prove their wider sustainability credentials. For example, in the EUTS, SAFUG's proposal was accepted[69] that only fuels certified as sustainable by the RSB or similar body would be zero rated.[70] SAFUG was formed by a group of interested airlines in 2008 under the auspices of Boeing Commercial Airplanes. Member airlines represent more than 15% of the industry, and signed a pledge to work towards SAF.[71][72]

In addition to SAF certification, the integrity of aviation biofuel producers and their product can be assessed by means such as Richard Branson's Carbon War Room,[73] or the Renewable Jet Fuels initiative.[74] The latter works with companies such as LanzaTech, SG Biofuels, AltAir, Solazyme, and Sapphire.[75]

Along with her co-authors, Candelaria Bergero of the University of California's Earth System Science Department stated that "main challenges to scaling up such sustainable fuel production include technology costs and process efficiencies", and widespread production would undermine food security and land use.[76]

Certified processes
AbbreviationConversion ProcessPossible FeedstocksBlending RatioCommercialization Proposals / Projects
HEFA-SPKSynthesized paraffinic kerosene produced from hydroprocessed esters and fatty acidsBio-Oils, Animal Fat, Recycled Oils50%World Energy, Universal Oil Products, Neste, Dynamic Fuels, EERC
FT-SPKFischer-Tropsch hydroprocessed synthesized paraffinic keroseneCoal, Natural Gas, Biomass50%Fulcrum Bioenergy, Red Rock Biofuels, SG Preston, Kaidi Finland, Sasol, Shell Oil Company, Syntroleum
SIP-HFSSynthesized kerosene isoparaffins produced from hydroprocessed fermented sugarsBiomass-derived sugar10%Amyris (company), Total S.A.
SPK/ASynthesized kerosene with aromatics derived by alkylation of light aromatics from non-petroleum sourcesCoal, Natural Gas, Biomass50%Sasol
ATJ-SPKAlcohol-to-jet synthetic paraffinic keroseneBiomass-derived ethanol or isobutanol50%Gevo, Cobalt, Universal Oil Products, Lanzatech, Swedish Biofuels, Byogy

See also

References
  1. "Sustainable aviation fuel market demand drives new product launches". Investable Universe. 2020-12-04. Retrieved 2022-12-12. Note: Investable Universe>About
  2. Doliente, Stephen S.; et al. (10 July 2020). "Bio-aviation Fuel: A Comprehensive Review and Analysis of the Supply Chain Components". Frontiers in Energy Research. 8. doi:10.3389/fenrg.2020.00110.
  3. "Developing Sustainable Aviation Fuel (SAF)". IATA.
  4. Bauen, Ausilio; Howes, Jo; Bertuccioli, Luca; Chudziak, Claire (August 2009). "Review of the potential for biofuels in aviation". CiteSeerX 10.1.1.170.8750.
  5. Mark Pilling (2021-03-25). "How sustainable fuel will help power aviation's green revolution". Flight Global.
  6. "A Greener Future?". Aircraft Illustrated. March 2009.
  7. Ron Oxburgh (28 February 2008). "Through biofuels we can reap the fruits of our labours". The Guardian.
  8. Patrick Barta (24 March 2008). "As Biofuels Catch On, Next Task Is to Deal With Environmental, Economic Impact". Wall Street Journal.
  9. Bailis, R. E.; Baka, J. E. (2010). "Greenhouse Gas Emissions and Land Use Change from Jatropha Curcas-Based Jet Fuel in Brazil". Environmental Science & Technology. 44 (22): 8684–91. Bibcode:2010EnST...44.8684B. doi:10.1021/es1019178. PMID 20977266.
  10. "Waste and residues as raw materials". Neste Corporation website. 15 May 2020.
  11. "Neste and Lufthansa collaborate and aim for a more sustainable aviation" (Press release). Neste Corporation website. October 2, 2019.
  12. "KLM Group's CO2 emission reduction targets for 2030 approved by SBTi" (Press release). KLM website. 16 December 2022. Retrieved 2023-01-02.
  13. "TotalEnergies and Air France KLM agree sustainable jet fuel deal". Reuters. 5 December 2022. Retrieved 2023-01-02.
  14. "NASA confirms biofuels reduce jet emissions". Flying magazine. March 23, 2017. Note: Firefox 'does not trust' the weblink 2022-12-22.
  15. Pharoah Le Feuvre (18 March 2019). "Are aviation biofuels ready for take off?". International Energy Agency.
  16. "First biofuel flight touches down". BBC News. 24 February 2008.
  17. "Our Commitment to Sustainable Options" (PDF). Sustainable Aviation Fuel Users Group.
  18. "First Airlines and UOP Join Algal Biomass Organization". Green Car Congress. 19 June 2008.
  19. "Carbon-Neutral Growth By 2020" (Press release). IATA. 8 June 2009. Archived from the original on 2021-04-14. Retrieved 2020-12-06.
  20. "Airlines May Get 1% of Fuel From Biofuels By 2015, Boeing Says". Bloomberg. 22 July 2010.
  21. "50 Percent Biofuels Now Allowed in Jet Fuel". Renewable Energy World. 1 July 2011.
  22. "Aviation Fuel Standard Takes Flight". ASTM. September–October 2011. D7566 Revision Adds Bioderived Components
  23. "Airlines Win Approval to Use Biofuels for Commercial Flights". Bloomberg. 1 July 2011.
  24. Bettina Wassener (9 Oct 2011). "Airlines Weigh the Advantages of Biofuels". NY Times.
  25. "ASTM approves 7th annex to D7566 sustainable jet fuel specification: HC-HEFA". Green Car Congress. May 14, 2020. Retrieved August 8, 2021.
  26. Meg Cichon (2 December 2011). "FAA Awards $7.7 Million for Advancement of Aviation Biofuels". Renewable Energy World.
  27. "British Airways to buy jet fuel from city waste". Reuters. 16 Feb 2010.
  28. "AirportWatch | Solena, the company meant to be producing jet fuel from London waste for BA, goes bankrupt". www.airportwatch.org.uk. Retrieved 2021-08-30.
  29. Chris Reddy; Greg O'Neil (28 January 2015). "Jet Fuel from Algae? Scientists probe fuel potential in common ocean plant". Oceanus magazine. Woods Hole Oceanographic Institution.
  30. "From green slime to jet fuel: algae offers airlines a cleaner future". Reuters. 15 June 2016.
  31. "Sustainable Aviation Fuels Guide" (PDF). ICAO. Dec 2018.
  32. Wessof, Eric (19 April 2017). "Hard Lessons From the Great Algae Biofuel Bubble". Greentech Media.
  33. 2021-03-25T14:13:00+00:00. "How sustainable fuel will help power aviation's green revolution". Flight Global. Retrieved 2021-03-28.
  34. "Sustainable Aviation Fuels Fact sheet" (PDF). IATA. May 2019.
  35. "Expanding our commitment to powering more flights with biofuel" (Press release). United Airlines. May 22, 2019.
  36. "Virgin Australia's sustainable aviation fuel flies one million kilometres" (Press release). Virgin Australia. 17 June 2019.
  37. Kerry Reals (Apr 26, 2019). "Biofuel Market Is Nearing A Tipping Point". Aviation Week & Space Technology.
  38. "BA begins offsetting domestic flight emissions". Flightglobal. 3 January 2020.
  39. Guy Norris (February 4, 2021). "Boeing Moves Forward With Airbus A321XLR-Competitor Plan". Aviation Week.
  40. "Standard Specification for Aviation Turbine Fuel Containing Synthesized Hydrocarbons". www.astm.org.
  41. Snijders, T. A.; Melkert, J. A. (December 22, 2011). "Evaluation of safety, performance and emissions of synthetic fuel blends in a Cessna Citation II". Conference Proceeedings of the 3AF/AIAA Aircraft Noise and Emissions Reduction Symposium, 25–27 October 2011, Marseille, France – via repository.tudelft.nl.
  42. Starck, Laurie; Pidol, Ludivine; Jeuland, Nicolas; Chapus, Thierry; Bogers, Paul; Bauldreay, Joanna (January 2016). "Production of Hydroprocessed Esters and Fatty Acids (HEFA) – Optimisation of Process Yield" (PDF). Oil & Gas Science and Technology – Revue d'IFP Energies nouvelles. 71 (1): 10. doi:10.2516/ogst/2014007. S2CID 45086444. Retrieved 3 November 2022.
  43. "Biofuel Factsheet - Aviation Biofuels" (PDF). European Technology Innovation Platform - Bioenergy. 2017. Archived (PDF) from the original on 29 June 2022. Retrieved 3 November 2022.
  44. "Producing sustainable aviation fuel".
  45. "ATJ-SPK (Alcohol to Jet Synthetic Paraffinic Kerosene) – Advanced BioFuels USA".
  46. "Jet Fuel Derived from Ethanol Now Eligible for Commercial Flights". Archived from the original on 2022-01-25. Retrieved 2020-12-22.
  47. Voegele, E. November 2009. "Waste to ethanol projects move forward", Ethanol Producer Magazine
  48. "Interview: LanzaTech CEO Jennifer Holmgren". www.triplepundit.com.
  49. Nagaraju, Shilpa; Davies, Naomi Kathleen; Walker, David Jeffrey Fraser; Köpke, Michael; Simpson, Séan Dennis (October 18, 2016). "Genome editing of Clostridium autoethanogenum using CRISPR/Cas9". Biotechnology for Biofuels. 9 (1): 219. doi:10.1186/s13068-016-0638-3. PMC 5069954. PMID 27777621.
  50. "Archived copy" (PDF). Archived from the original (PDF) on 2021-06-23. Retrieved 2021-11-23.{{cite web}}: CS1 maint: archived copy as title (link)
  51. "SOLAR-JET project terminated and succeeded by SUN-TO-LIQUID project". solar-jet.aero.
  52. "Press corner". European Commission - European Commission.
  53. "SUN to LIQUID project - SUN to LIQUID project". www.sun-to-liquid.eu.
  54. "Ways to make aviation fuel green". The Economist. August 17, 2022. ISSN 0013-0613. Retrieved 2023-02-23.
  55. "AGE-85 (Aviation Grade Ethanol)". South Dakota State University. 2006. Archived from the original on 2008-05-15.
  56. "Indiana Airline Fuel Developer Moves Ahead With Testing" (Press release). Purdue Research Park. December 14, 2009.
  57. Grady, Mary (December 15, 2009). "Efforts Move Forward To Produce Alternative Aviation Fuels".
  58. "Technical Report: Near-Term Feasibility of Alternative Jet Fuels" (PDF). Sponsored by the FAA. Authored by MIT staff. Published by RAND Corporation. Retrieved August 22, 2012.
  59. "Biodiesel FAQ" (PDF). University of Kentucky College of Agriculture, Food, and Environment. 2006. Retrieved August 22, 2012.
  60. "AFRL discovering what's "bugging" military aircraft". U.S. Air Force. 11 September 2016.
  61. "Sustainable Aviation Fuel: Review of Technical Pathways" (PDF). United States Department of Energy. Sep 2020.
  62. Kerry Reals (Oct 10, 2017). "Glacial Pace Of Advancements In Biofuel Threatens Emissions Targets". Aviation Week & Space Technology.
  63. "Ways to make aviation fuel green". The Economist. 2022-08-17. ISSN 0013-0613.
  64. "Sustainability schemes for biofuels". European Commission/Energy/Renewable energy/Biofuels. Retrieved 1 April 2012.
  65. "Sustainable Aviation Fuel". Qantas. Retrieved 2013-10-24.
  66. "RSB Roundtable on Sustainable Biomaterials | Roundtable on Sustainable Biomaterials" (PDF). Rsb.epfl.ch. 2013-10-17. Archived from the original (PDF) on 2011-12-22. Retrieved 2013-10-24.
  67. "Our Commitment to Sustainable Options". Archived from the original on April 25, 2012. Retrieved March 29, 2012.
  68. "Sustainable Aviation Fuel Users Group – SAFUG". Safug.org. Retrieved 2013-10-24.
  69. "Revision of the EU Energy Tax Directive - technical press briefing" (PDF). Ec.europa.eu. Retrieved 2013-10-24.
  70. "Sustainable Aviation Fuel Users Group : European Section" (PDF). Safug.org. Retrieved 2013-10-24.
  71. "Environment and Biofuels | Boeing Commercial Airplanes". Boeing.com. Retrieved 2013-10-24.
  72. "SAFUG Pledge; Boeing Commercial Airplanes". Safug.org. Retrieved 2015-07-10.
  73. "Renewable Jet Fuels". Carbon War Room. Archived from the original on 2013-10-30. Retrieved 2013-10-24.
  74. "Welcome". Renewable Jet Fuels. Archived from the original on 2013-10-29. Retrieved 2013-10-24.
  75. "Sustainable Sky Institute". Sustainable Sky Institute. Retrieved 2016-04-26.
  76. Bergero, Candelaria; et al. (30 January 2023). "Pathways to net-zero emissions from aviation". Nature Sustainability. 6 (4): 404–414. doi:10.1038/s41893-022-01046-9. S2CID 256449498.

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