Biofuels for Air Travel

Biofuels in Aviation - An Overview

Since 2003, various studies and reports have investigated the potential for use of biofuels in aviation. In recent months, EC-funded R&D projects have been initiated to map a way forward for the introduction of sustainable biofuels to help reduce dependence on fossil fuels in air transport and reduce GHG emissions by the air industry.

Globally, various feedstocks and conversion technologies for production of biofuels for aviation are currently being investigated.

© Copyright Boeing
A Virgin Atlantic 747-400 prepares for take-off from London Heathrow to Amsterdam using a sustainable biofuel blend composed of babassu and coconut oils blended with kerosene-based jet fuel. Boeing partnered with GE, Imperium Renewables and Virgin Atlantic to conduct the first commercial flight using sustainable biofuels as part of its efforts to guide the industry toward fuels that have a low-carbon-lifecycle footprint to help reduce impacts to climate change

Hydrogen has also been suggested as an aircraft fuel of the future. In reality, hydrogen aircraft would require new engines and airframes, which are unlikely to be seen for at least several decades. Hence, at the present time novel liquid fuels are the only realistic alternative for commercial air transport. These include new fuels synthesised from gas (GTL) and coal (CTL) as well as those derived from biomass.

The potential use of synthetic jet fuels is just one of a wide range of long term solutions being introduced or considered to reduce the sustainability of air transport. In the more immediate future, projects such as the €1.6 billion public-private CLEAN SKY Joint Technology Initiative (JTI) aim to increase efficiency by accelerating development of new engine and aircraft design and other measures.

At the same time, biofuels are gaining increasing interest from airlines and airplane manufacturers. Following successful demonstration flights of commercial aircraft using various biofuel blends, the ASTM Aviation Fuel Subcommittee in June 2009 passed a new fuel specification that would enable the use of synthetic fuels (including biofuels) in commercial air transport.

In September 2008, the Sustainable Aviation Fuel Users Group SAFUG was formed to accelerate the development and commercialization of sustainable aviation fuels. Support and advice is provided by leading environmental organisations including the Natural Resources Defense Council and the Roundtable on Sustainable Biofuels (RSB). SAFUG members (including many of the world's leading airlines) agree to contribute to robust sustainability and certification regimes via the RSB global multi-stakeholder process. All members subscribe to a sustainability pledge stipulating that any sustainable biofuel must perform as well as, or better than, kerosene-based fuel, but with a smaller carbon lifecycle.

UPS the world's largest package delivery company has also indicated that it is considering use of biofuels to help meet its pledge to cut the carbon emissions of its airline by an additional 20% by 2020.

Biofuels in Aviation - Studies and Reports

A 2003 study by Imperial College - The Potential for Renewable Energy Sources in Aviation - investigated renewable alternatives to kerosene, the fuel currently used by jet aircraft. This concluded that bioethanol cannot be used for air transport due to its low energy density, and because it doesn't combust effectively in 'thin air' at high altitude. The Imperial study also concluded that methanol and biogas are unsuitable for air transport for both technical and safety reasons. However, hydrogen, Fischer-Tropsch (FT) kerosene and biodiesel could all theoretically be used in aviation.

More recently, research has focued on production of 'bio jet oil' via a number of novel routes such as catalytic pyrolysis / refining and catalysis of plant sugars.

The 2007 report Alternative Technology Options for Road and Air Transport published by ETAG (European Technology Assessment Group) for the European Parliament, suggested that due to tighter operational and safety criteria for novel aviation fuels, biofuels will predominantly be used in the road transport sector for the forseeable future. However, this assessment was made before the successful test flights of Boeing and AIRBUS aircraft, and the landmark ASTM Aviation Fuel Subcommittee decision to establish a specification for synthetic aviation fuels.

The establishment of SAFUG and increasing investments in biojet fuel R&D indicate that biofuels are now most definitely on the radar of major airlines.

The ICAO Workshop on Aviation and Alternative Fuels (WAAF) held on 10-12 February 2009 included 30 presentations, with several covering use of biofuels.

In the UK, the Sustainable Aviation strategy group brings together researchers, airlines and other stakeholders contributing to a number of key documents proposing a way forward for sustainabile air travel.

In July 2009, a research summary was published by Policy Exchange, UK entitled Green Skies Thinking - promoting the development and commercialisation of sustainable jet fuels

© Copyright Boeing
A Boeing lab technician conducts automated freeze-point testing on jet fuel samples at the Boeing Commercial Airplanes Fuels and Lubricants Test Laboratory in Seattle. Boeing is exploring second-generation biofuel testing to identify renewable alternative fuel sources for aviation uses as part of the company's environmental initiative.

Biofuels in Aviation - Feedstocks and conversion technologies

2nd Generation biofuels derived from Jatropha and Camelina have been successfully blended with Jet A fuel in demonstration flights.

Airbus has teamed with Honeywell Aerospace; UOP, a Honeywell Company; International Aero Engines (IAE); and JetBlue Airways to pursue development of a sustainable second-generation biofuel for use in commercial aircraft.

In August 2008, The world's first algal based jet fuel was produced by Solazyme. It passed the most critical ASTM D1655 specification tests.

In January 2009, the Defense Advanced Research Projects Agency (DARPA) awarded Science Applications International Corporation (SAIC) a $25m contract to develop an integrated process for developing Jet Fuel (JP-8 replacement) from algae.

A 100% renewable jet fuel produced by the Energy & Environmental Research Center (EERC), University of North Dakota, under a $4m contract with DARPA has been tested by the AFRL and met JP-8 specification criteria.

Arizona State University Laboratory for Algae Research & Biotechnology, Heliae Development, LLC and Science Foundation Arizona are also collaborating in the development of kerosene-based jet fuel derived from algae.

The Virent BioForming® Process for catalytic conversion of plant sugars into liquid hydrocarbon fuels could also potentially be used to produce jet fuel from sustainable feedstocks.

EC Projects on use of Sustainable Biofuels in Aviation

SWAFEA Sustainable Way for Alternative Fuel and Energy in Aviation
A 26 month study (starting May 2009) with €5.1m funding from DG-TREN involving 19 partners from aviation and fuel industries, airlines, research and consultancy to develop a vision and road map for sustinable deployment of alternative fuels and energies in aviation

ALFA-BIRD
ALFA-BIRD gathers a multi-disciplinary consortium that aims to develop the use of alternative fuels in aeronautics, with key industrial partners from aeronautics (engine manufacturer, aircraft manufacturer) and fuel industy, and research organization covering a large spectrum of expertise in fields of biochemistry, combustion as well as industrial safety. Bringing together their knowledge, the consortium will develop the whole chain for clean alternative fuels for aviation. The most promising solutions will be examined during the project, from classical ones (plant oils, synthetic fuels) to the most innovative, such as new organic molecules. Based on a first selection of the most relevant alternative fuels, a detailed analysis of up to 5 new fuels will be performed with tests in realistic conditions.

Clean Sky JTI

The Clean Sky JTI is one of the largest European research projects ever, with a budget estimated at €1.6 billion, equally shared between the European Commission and industry, over the period 2008 - 2013. This public-private partnership will speed up technological breakthrough developments and shorten the time to market for new solutions tested on Full Scale Demonstrators.

"Clean Sky will demonstrate and validate the technology breakthroughs that are necessary to make major steps towards the environmental goals sets by ACARE - Advisory Concil for Aeronautics Research in Europe - the European Technology Platform for Aeronautics & Air Transport and to be reached in 2020:"

50% reduction of CO2 emissions through drastic reduction of fuel consumption
80% reduction of NOx (nitrogen oxide) emissions
50% reduction of external noise
A green product life cycle: design, manufacturing, maintenance and disposal / recycling

This will be achieved by technologies in areas such as loads and flow control, Aircraft Energy Management, NOx and CO2 reduction, rotorcraft, regional aircraft, trajectory management, smart fixed-wing aircraft, etc.

Demonstration flights using biofuel blends

In February 2008, Virgin Atlantic carried out a test flight of a Boeing 747 Jumbo from London to Amsterdam with a 20% blend of coconut and babassu oil in one of the aircraft's fuel tanks. However, the company concedes that there are no immediate plans to use similar mixtures in commercial flights. More info

Also in February 2008, an Airbus A380 used a 40% blend of GTL (gas to Liquid) in a flight from Bristol to Toulose, paving the way for future use of BTL. "Analysis of data from the A380’s historic flight powered by an alternative fuel derived from gas (GTL) has shown that use of the GTL blend had no adverse impact on the engine, aircraft systems or materials, and that it behaved like conventional kerosene."

In December 2008, a blend of 2nd Generation biofuel from Jatropha was used in one Rolls Royce engine for a two hour test flight of an Air New Zealand Boeing 747-400. More info

Bio-Derived Synthetic Paraffinic Kerosene (Bio-SPK) has been used by Boeing in flight tests of several different aircraft between 2006 and 2009. Performance was as good as (or better than) Jet A fuel.
View evaluation report

In January 2009, Japan Airlines (JAL) used a 50:50 blend of Jet A fuel and 2nd generation synthetic kerosene, mainly produced from Camelina, in one Pratt & Whitney engine of a Boeing 747-300.
View JAL press release