The development of alternative fuels is gathering speed — the interest being driven by environmental and cost concerns.
For aircraft jet engines wide scale deployment is still some way off. Any new fuel would have to meet a number of criteria, making research a delicate balancing act. In addition to the obvious need for reducing carbon dioxide emissions (CO2), it would help to limit overall fuel dependency and price as well as to become compatible with existing infrastructure. In some cases, this not only precludes redesigns of jet engines but also storage and distribution methods at the airport.
Francis Couillard, CFM, international general manager of environmental affairs, also identifies the need to meet stringent characteristics such as thermostability and heating values. “This would affect the size of the tank,” he says. “For example hydrogen would need a tank four times as large as kerosene.”
Most research is centred on the Fischer-Tropsch (FT) process, a technology dating from the World War II when Germany realized fuel shortages could become crucial. FT effectively produces a synthetic crude oil from a natural resource such as coal to which conventional refining processes can then be applied.
The benefits of FT include compatibility with current hardware and distribution methods and a relatively abundant supply of raw material. However, Couillard says environmentally-speaking there is no interest in producing fuel from coal because the process still relies on a natural resource, generating greenhouse emissions and causing enviromental damage.
“The same reasons limit gas usage,” he says. “It means the most efficient way forward is biomass, which could be wood, plants or organic residues. Biomass or BTL (Biomass to Liquid) has the potential to reduce CO2 emissions by up to 80 percent.”
Unfortunately, there is no industrialization of biomass as yet and the matter is largely out of engine manufacturers’ hands, involving as it does the fuel companies, State authorities and all other stakeholders.
“There is a lot to demonstrate and validate,” says Couillard. “Substantiation is a long process and it needs a lot more work worldwide.”
Only a handful of companies have commercialized their FT technology. Sasol in South Africa is one example. The company has been producing semi-synthetic fuels (50 percent normal fuel and 50 percent FT fuel) for the aviation industry since 1999, spurred on by shortages in Johannesburg.
Certification for a synthetic jet fuel is nevertheless drawing close. Pratt&Whitney, General Electric and Rolls Royce as well as industry partners such as Honeywell are in the final stages of obtaining approval with tests concluding in three key areas: endurance, ignition and emissions.
CFM mother companies’ Snecma (SAFRAN Group) and General Electric, are also involved in the development of alternative aviation fuels. Snecma is currently working with laboratories and universities worldwide and has helped define specifications of future bio fuels in a European context. A SAFRAN group company has also performed some tests of a gas turbine using a synthetic fuel.
Meanwhile, the first BTL plant should come online in late 2007, a partnership between Shell and CHOREN Industries in Germany. This will use a wood chips base to make the synthetic fuel.
Transforming ground ops
While widespread biofuel for jet engines is a few years away, work on so-called ‘first generation’ fuels such as bioethanol promise much for conventional engines.
The ground support fleet could be transformed — and may well need to be. The US Environmental Protection Agency and Federal Aviation Administration both have airport emission reduction programs in place while environmental concern remains a hot topic in Europe.
Eastern Aviation Fuels is the exclusive distributor of branded aviation fuels for Shell Oil Products US.
Daniel M. Hancock talks about the changes resulting from alternative fuels and advanced powertrain technologies.
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