On October 19, 2004, the world’s first exclusively biofuel powered production aircraft received its certification, allowing it to be flown operationally. That aircraft was (and is) the Neiva (now Embraer) EMB-202A Ipanema crop duster. This is the most recent version of a design that first flew in 1970 as the Embraer EMB-200 Ipanema, and complements the conventionally fuelled EMB-202 model.
Powered by a Lycoming IO-540-K1J5 piston engine, the EMB-202A uses 100% ethanol fuel derived from sugar cane. Brazil has already developed a nationwide network for sugar-cane-derived ethanol fuel for motor vehicles, creating the supply framework which made the EMB-202A both feasible and competitive. Further, maintenance costs are lower than for its conventionally powered sister. In addition, while the conventionally fuelled EMB-202 has a power output of 300 HP (about 221 kW), that for the EMB-202A is higher at 320 HP (about 235 kW). The EMB-202A consequently has a better take-off, climbing, speed and altitude performance than the EMB-202.
Up to October 2014, 269 EMB-202As had been sold, and another 205 EMB-202s converted to EMB-202As, giving a total biofuel- powered fleet of 474. This is about 40% of the total Ipanema fleet operating in Brazil today. “Ethanol is efficient and costs less and it is an alternative that pleased customers – many of whom have their own sugar cane plantations,” highlighted Embraer Ipanema sales manager Fábio Bertoldi Carretto on the tenth anniversary of the certification of the EMB-202A. “Not surprisingly, over 80% of new [Ipanema] aircraft are sold with [sic] this configuration.” On average, ethanol is 25% cheaper than conventional fuel.
Unfortunately, ethanol is totally unsuitable as a fuel for turbine (turbofan, turbojet and turboprop) engines, as it lacks the required energy density. Jet and turboprop engines use kerosine-grade fuels, sometimes referred to as aviation turbine fuels but more frequently simply called jet fuels. The most widely used type is Jet A-1. For this reason, research into biofuels for jet and turboprop aircraft has been focused on what are called second-generation biofuels.
Biofuels are fuels produced from biological resources – algae, plants, bushes as well as waste biomass – that are renewable. When burnt as fuel, they do not release additional carbon dioxide (CO2) into the atmosphere, as the CO2 they release was originally absorbed by their precursor plants when they were alive. In principle, biofuels could be derived from any plant material. In practice, given the energy density required by fuels for jet and turboprop engines, and the aviation industry’s desire to avoid using food crops as fuel sources (which would drive up food prices), the list of feasible alternatives is more restricted.
From an airline point of view, there are three main reasons to use biofuels. These are: creating a diversified fuel supply, economic (and social) benefits, and environmental benefits.
On the environmental front, although bio- fuels are not quite carbon neutral – fuel has to be expended in raising, harvesting, processing and transporting them – they do release about 89% less emissions over their lifecycles than fossil fuels do. Biofuels also do not contain impurities such as sulphur, so reducing sulphur dioxide and soot emissions as well.
Fuel accounts for some 30% of airline operating costs, according to the International Air Transport Association (Iata). In recent months, the global oil price trend has been downwards, but the unpredict- ability and frequent volatility in the price are constant concerns for the aviation industry, making planning and budgetting for operational costs very difficult. Biofuels could, in the future, cut costs. The raising of nonfood second- generation biofuel feedstock crops on land that is suitable for them but marginal for food crops would also bring socioeconomic benefits to the rural areas concerned. Because they can be produced in a wide variety of locations, using different feedstocks, biofuels provide a diversified fuel supply. This can greatly reduce price volatility.
The development, testing and evaluation of biofuels for aviation, and the development of the infrastructure to sustainably produce and distribute them and ensure their availability at airports worldwide are major concerns of the Air Transport Action Group (Atag), which is an industry group – the only such group which represents all elements of the air transport industry. Its membership is divided into four categories: funding members, associate members, active members and partnership organisations. The funding members are (in alphabetical order): Airbus, ATR, the Airports Council International, Boeing, Bombardier, CFM, the Civil Air Navigation Service Organisation, Embraer, GE Aviation, Honeywell, Iata, Pratt & Whitney, Rolls-Royce and Safran.
Another global body, with a specific focus on driving forward the development and commercialisation of sustainable biofuels for aviation is the Sustainable Aviation Fuels Users Group, which was set up in 2008. Its membership comprises 27 of the world’s leading airlines and air freight operators from all continents and including South African Airways (SAA). Airliner manufacturers Airbus, Boeing and Embraer are among the affiliate members.
Second-generation nonfood biofuel crops include, but are not restricted to, algae, camelina, jatropha and halophytes. All algae contain lipid oil, although the amount varies from species to species. Camelina is an annual, many-branched plant which grows to between 30 cm and 120 cm in height and produces seed pods with many small oily seeds. It can be grown on marginal agricultural lands. In nature, Camelina is very widely distributed around the world. Jatropha is a bush that usually grows to between 3 m and 5 m in height. Again, it produces oily seeds and grows well in poor and marginal soils. It is drought-resistant. Halophytes are plants that grow, indeed can thrive, in water with a high salinity content. There are many families of halophytes and the seeds of the Salicornia species could be used to produce oil.
Although these are currently the main feedstocks for second-generation aviation biofuels, they are by no means the only ones. In Australia, for example, they are looking at Mallee trees (a species of eucalyptus) as a feedstock. It all cases, oil is extracted from the plant itself, or (more usually) it seeds or even its leaves. This oil is then refined. Following a different track, US company Amyris, which has a Brazilian subsidiary, has developed an aviation jet biofuel from sugar cane, known as farnesane.
Aviation biofuels can also be produced from used cooking oils and biomass from municipal waste. The first plant to produce biofuels from municipal waste biomass is now being built by a partnership of British Airways (BA) and Solena Fuels, at Thurrock, in Essex, near London. It will produce 50 000 t/y of jet biofuel, all of which will be bought by BA.
Over the past several years, a number of projects, programmes and industry collaborations to investigate and develop jet biofuels have been set up in a number of countries. These include Australia, Brazil (with two programmes), Canada, Chile, France, Germany, India, Mexico, the Netherlands, New Zealand, Spain, Thailand, the United Arab Emirates, the UK and the US (with three programmes, two of which are regionally based). In addition, there are also regional and multilateral collaborations under way, such as the Nordic Initiative for Sustainable Aviation, which embraces Denmark, Finland, Iceland, Norway and Sweden and the South-East Asia Sustainable Aviation Fuel Initiative.
South Africa is another country interested in the development and production of biofuels for jet aircraft. Following the National Climate Change Response White Paper of October 2011, all State-owned companies were ordered to draw up policies concerned with climate change and develop detailed plans to cut their carbon emissions. These instructions naturally applied to State-owned national carrier SAA.
In September 2012, the Department of Public Enterprises (DPE) organised a Multi-Partner Aviation Biofuels Workshop, near Pretoria. This was attended by a wide range of interested parties, including potential suppliers, users, academics, development agencies and others. It was suggested that SAA employ biofuels for 50% of its jet fuel needs at O R Tambo International Airport by 2020. It quickly became clear that such a target was extremely unrealistic, and there has since been little public activity regarding aviation biofuels by the DPE.
However, SAA has been far from inactive. In October 2013, the airline signed a memorandum of understanding (MoU) with Boeing to cooperate in the development and implementation of a “sustainable aviation biofuel supply chain in Southern Africa”, in the words of their joint press release. Then, in August last year, SAA and Boeing announced that they had formed a partnership with Dutch aviation biofuels company SkyNRG to produce aviation biofuel from cross-bred nicotine-free tobacco plants. As a result, “we can leverage knowledge of tobacco growers in South Africa to grow a marketable biofuel crop without encouraging smoking”, noted SAA environmental affairs head Ian Cruickshank at the announcement of the partnership.
The cross-bred tobacco plant is named Solaris. It was developed in Italy by a company named Sunchem Holdings, starting some 12 years ago. The development process, which maximises flower and seed production and minimises leaf production in the plant, did not involve any genetic modification. Solaris contains no nico- tine and cannot be used to make cigarettes. Test farming of the plant in South Africa started before the creation of the partnership between SAA, Boeing and SkyNRG. The plant is also being trialled in Brazil, Bulgaria, Egypt, Namibia and the US, as well as, of course, Italy.
“A typical season, over three harvests, yields 9 t of seed per hectare, which, following a process of mechanical extraction, equates to 3 t of oil and 6 t of high-protein press cake (which is an animal feed integrator),” reports Sunchem Biofuel Development South Africa project manager Samantha Bartle. So the plant can simultaneously act as a feedstock for aviation biofuels and animal feeds. “The conversion of the oil into jet [fuel] is 1.4 t of oil = 1 t of biojet fuel.”
FROM TESTING TO SERVICE
Potential biofuels for jet aircraft were and are first developed and tested in a laboratory. They must meet exactly the same specifications as those for Jet A-1 fuel. This is because fuel, on modern airliners, is not just used to drive the engines. It also serves as a lubricant, as a cooling fluid and as a hydraulic fluid. The specifications for Jet A-1 are a minimum flashpoint of 38 ºC, a freezing point of at least –47 ºC, a minimum combustion heat of 42.8 MJ/kg (this is the amount of energy released during combustion per kilogramme of fuel), a maximum viscosity of 8 000 mm2/s, a sulphur content of no more than 0.30 parts per million and a density of between 775 kg/m3 and 840 kg/m3.
Laboratory tests are followed by ground tests, with jet engines being run at different power settings, all the way from ground idle to take-off power. The time taken for the engine to start, the performance of the biofuel in acceleration and deceleration and the consistency of the fuel ignition in the engine are all tested. The engine exhaust is tested for emissions and smoke. And other tests ensure that the biofuel does not have an adverse effect on any of the materials used in the manufacture of the aircraft or the engines.
Only once all these tests have been completed can flight tests be undertaken. The first demonstration flight of a jet airliner using biofuel took place on February 24, 2008. A Virgin Atlantic Boeing 747 flew from London to Amsterdam using a blend of 20% biofuel and 80% Jet A-1. No passengers were carried. The biofuel employed was produced from coconut oil and babassu nut oil. A string of test flights by different operators followed, using jet and turboprop aircraft manufactured by Airbus, Bombardier, Boeing and Embraer, powered by engines from CFM International, General Electric, Pratt & Whitney and Rolls-Royce. Feedstocks used included algae, camelina, jatropha, sugar cane and used cooking oil.
The success of these flights has led international standards organisation ASTM International to approve jet biofuels produced from algae, waste biomass, oil seeds and sugar cane. These biofuels may be blended with Jet A-1 up to a ratio of 50:50. This cleared the way for the use of biofuels on scheduled commercial air services. The first commercial jet airliner flight using biofuel (blended with Jet A-1) was by KLM Royal Dutch Airlines, from Amsterdam to Paris, on June 29, 2011, using a Boeing 737-800 carrying 171 passengers. (KLM had previously carried out the first biofuel demonstration flight with passengers on board, on November 23, 2009.)
There have been many more passenger-carrying jet biofuel flights since then, in Europe, North America, South America, Asia and Australasia. And developments continue. On December 3, 2014, a Boeing 787 ‘ecoDemonstrator’ aircraft became the first aircraft to fly using “green diesel” fuel, widely used in terrestrial transport. The aircraft flew using a blend of 15% green diesel and 85% jet fuel to power its port (left side) engine. Green diesel uses vegetable oils, waste cooking oils and waste animal fats as its feedstocks.
Already in 2011, in his foreword to Atag publication Powering the Future of Flight, the group’s executive director, Paul Steele, wrote: “From a standing start just a few years ago, the aviation industry has embraced the concept of biofuels with enthusiasm . . . Rigorous testing, both on the ground and in the air, has shown that biofuels can deliver equal (and sometimes better) performance than the current fuel . . . The second- generation biofuels . . . when refined, are virtually identical to the Jet A-1 fuel we currently use. This means we can simply drop them into the current fuel supply . . . More biofuel can be added to the system as it comes on stream.”
Currently, jet biofuels are used in blends with Jet A-1, but, in principle, airliners could be flown using 100% biofuels in their tanks. “The [Solaris] biojet fuel produced is on speci- fication Jet A-1; hence, it could power a plane on its own,” points out Bartle. “The biggest challenge now lies in ensuring a steady, reliable, cost-effective and sustainable supply of this new energy source,” noted Steele in his foreword. The production, processing and/or refining and distribution infrastructure for aviation jet biofuels still needs to be developed. Bartle gives an idea of the scale required. “For example, SAA uses one-billion litres of jet fuel a year. This equates to about 433 000 ha of cultivation of Solaris, which is 3% of arable land in South Africa (and 10% of the under- utilised land in the country).” Moreover, prices have to be brought down. Ethanol for piston-engined aircraft may be cheaper than conventional fuel, but jet biofuels are still more expensive than Jet A-1.
Atag has proposed six steps in the creation of a viable aviation jet biofuels industry. These are: foster research into new feedstocks and refining processes; derisk public and private investments in aviation biofuels (the more investment, the greater the production, the lower the price); establish incentives for airlines to use biofuels as soon as possible; ensure commitment to strong international sustainability standards; understand the local opportunities for growth provided by the production and refining of feedstocks; and set up collaborations which embrace the entire biofuels supply chain.