Work is underway by a team that includes Qatar Airways, Airbus, Rolls-Royce, Shell and Qatar Petroleum to gain approval for a 50% mix of gas-to-liquid (GTL) kerosene with Jet A1 fuel by the end of this year. The advantages are expected to include lower emissions and greater range for the aircraft due to the higher energy density of the GTL kerosene.

Unveiled at last November's Dubai air show, the project's aim is to eventually enable widespread use of the synthetic fuel produced by Qatar's Pearl GTL complex.

Located in the country's industrial city Ras Laffan, Pearl GTL is the world's largest integrated GTL project, which will produce 140,000 barrels per day of high quality GTL fuels and product when it becomes fully operational in 2010, including 12,000 barrels per day (or around 500,000t per annum) of GTL kerosene. Testing this year is using fuel from the GTL pilot plant in Bintulu, Malaysia.

Talks are underway with the Delft University in the Nether­lands and Pratt & Whitney to undertake initial flight trials of GTL kerosene using its Cessna Citation flying laboratory.

Later tests involving an airliner will be undertaken by Qatar Airways teamed with Airbus and R-R, using one of the airline's A340-600s. "We will fly back-to-back trials with and without GTL measuring specific range to establish fuel efficiency and to evaluate emissions," says the airline. Once approval is received from the American Society of Test Methods, the US regulatory body for international fuel standards, GTL tests will be carried out on Qatar Airways revenue services.

Approval of the 50% GTL blend is expected by year-end and during 2009 tests will be undertaken to gradually increase the GTL mix. GTL is extremely pure so as the mix is increased there is insufficient lubrication for engine seals, meaning that hardware changes would be required.

Another solution is to mix GTL with a biofuel, which has impurities to aid lubrication. Qatar Airways is evaluating algae and vegetable based biofuels for the GTL mix, with the former viewed as the leading candidate.

From an environmental perspective, GTL kerosene reduces sulphur and particulate emissions, while its higher energy density improves fuel efficiency and lowers carbon emissions. "Widespread use at major hub airports like Heathrow will provide a noticeable improvement in local air quality," says Qatar Airways.

Source: Flight International