Aviation biofuel
Aviation biofuel is a biofuel used for aircraft. It is considered by some to be the primary means by which the aviation industry can reduce its carbon footprint. After a multi-year technical review from aircraft makers, engine manufacturers and oil companies, biofuels were approved for commercial use in July 2011. Since then, some airlines have experimented with using biofuels on commercial flights. The focus of the industry has now turned to second generation sustainable biofuels that do not compete with food supplies nor are major consumers of prime agricultural land or fresh water. NASA has determined that 50% aviation biofuel mixture can cut air pollution caused by air traffic by 50–70%.
The sustainable aviation fuels certification and production pace seems insufficient to meet the IATA target of halving the CO2 emissions by 2050.
The first flight using blended biofuel took place in 2008. Since then, more than 150,000 flights have used biofuels. Only five airports have regular biofuel distribution today, with others offering occasional supply. Trials of using algae as biofuel were carried out by Lufthansa, and Virgin Atlantic as early as 2008, although there is little evidence that using algae is a reasonable source for jet biofuels. By 2015, cultivation of fatty acid methyl esters and alkenones from the algae, Isochrysis, was under research as a possible jet biofuel feedstock.
As of 2017, there was little progress in producing jet fuel from algae, with a forecast that only 3 to 5% of fuel needs could be provided from algae by 2050. Further, algae companies that formed in the early 21st century as a base for an algae biofuel industry have either closed or changed their business development toward other commodities, such as cosmetics, animal feed, or specialty oil products.
Rationale for aviation biofuels
is poised to grow, as air travel increases and ground vehicles use more alternative fuels like ethanol and biodiesel. Currently aviation represents 2% of global emissions, but is expected to grow to 3% by 2050. In addition to building more fuel efficient aircraft and operating them more efficiently, or reducing air travel altogether, changing the fuel source is one of the few options the aviation industry has for reducing its carbon footprint. While solar, electric and hydrogen propelled aircraft are being researched, it is not expected they will be feasible in the near or medium term due to aviation's need for high power-to-weight ratio and globally compatible infrastructure.Concerns and challenges
that is stored for long periods of time is more likely to oxidize, especially at low temperatures, causing it to gel. Some additives improve the cold weather tolerance of biodiesel, but only by a few degrees. 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. Manufacturers are starting to use a synthetic rubber substitute called Viton for seals and hoses. Viton isn't adversely affected by biofuels. The US Air Force has found harmful bacteria and fungi in their biofueled aircraft, and use pasteurization to disinfect them.Industry commitments and collaborations
The International Air Transport Association supports research, development and deployment of alternative fuels. IATA thinks a 6% share of sustainable 2nd generation biofuels is achievable by 2020, and Boeing supports a target of 1% of global aviation fuels by 2015. This is in support of the goals of the aviation industry reaching carbon neutral growth by 2020 and a 50% decrease in carbon emissions by 2050A group of interested airlines has formed the Sustainable Aviation Fuel Users Group. The group was formed in 2008 in cooperation with support from NGOs such as Natural Resources Defense Council and The Roundtable For Sustainable Biofuels. Member airlines represent more than 15% of the industry, and all member CEOs have signed a pledge to work on the development and use of sustainable biofuels for aviation.
Boeing is joining other aviation-related members in the Algal Biomass Organization.
Production routes and sources
is a mixture of a large number of different hydrocarbons. The range of their sizes 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. Only tests have been done so far with blending in SPK in considerably higher concentrations.
Bio-SPK
The first route involves using oil which is extracted from plant sources like Jatropha, algae, tallows, other waste oils, Babassu and Camelina to produce bio-SPK by cracking and hydroprocessing.The growing of algae to make jet fuel is a promising but still emerging technology. Companies working on algae jet fuel are 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
The second route involves processing solid biomass using pyrolysis to produce pyrolysis oil or gasification to produce a syngas which is then processed into FT SPK.ATJ-SPK
Research is also being done on the alcohol-to-jet pathway where alcohols such as ethanol or butanol are de-oxygenated and processed into jet fuels. Some companies such as LanzaTech have already managed to create ATJ-SPK from CO2 in flue gases. The ethanol is hereby produced from CO in the flue gases using microbes. LanzaTech has successfully demonstrated its technology at Pilot scale in NZ –using Industrial waste gases from the steel industry as a feedstock for its microbial fermentation.Future production routes
Routes that use synthetic biology to directly create hydro-carbons are being researched.Also, the production of Fischer-Tropsch hydro-carbon fuels through the use of a solar reactor is being researched by the SUN-TO-LIQUID project.
Commercial and demonstration flights
Since 2008, a large number of test flights have been conducted, and since ASTM approval in July 2011, several commercial flights with passengers have also occurred.Demonstration flights
Commercial flights
Regular flights
By 2019, Virgin Australia has fueled more than 700 flights and flown more than 1 million kilometers, domestic and international, using Gevo's alcohol-to-jet fuel. 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.British Airways wanted to convert household waste into jet fuel with Velocys.
United Airlines committed to of sustainable aviation fuel for 10 years from Fulcrum BioEnergy, after its $30 million investment in 2015, and will develop up to five biofuel factories near its hubs.
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.
At its sites in Singapore, Rotterdam and Porvoo, Finland's Neste should improve its renewable fuel production capacity from a year by 2020, and is increasing its Singapore capacity by to reach in 2022 by investing €1.4 billion.
Environmental effects
A life cycle assessment by the Yale School of Forestry on jatropha, one source of potential biofuels, estimated 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. In addition, biofuels do not contain sulfur compounds and thus do not emit sulfur dioxide.Many different standards exist for certification of sustainable biofuels. One such standard often cited by airlines is the one developed by the Roundtable For Sustainable Biofuels. Nearly all such standards include a minimum amount of greenhouse gas reduction and consideration that biofuels do not compete with food.