Many airlines have conducted biofuel test flights over the past few years and, while individual fuel compositions may have varied, all used mixtures of conventional kerosene with biofuel, typically camelina or jatropha. Nothing more than such 50:50 fuel blends is permitted, anyway - and the biofuels were used in one aircraft engine while the other ran on Jet A1.
Every time, airline executives were wheeled out to say that the biofuel performed just as well as traditional, fossil-based kerosene, without posing major technical difficulties, and that the green crops offered a carbon-cutting way forward to more sustainable aviation.
Given that gas turbine engines are, in principle, quite simple powerplants, which can be fired with varying fuels (coal dust has, for example, been used for industrial gas turbines), such revelations come as no surprise. Instead, they begged the question: were biofuel test flights about improving scientific understanding, or perhaps more about spinning the PR wheel to establish an airline's green credentials?
However, when Lufthansa last year joined the group of airlines that have tested biofuel in flight, the carrier added value to the debate by employing the 50:50 biofuel blend on one aircraft over a six-month period, in order to assess any potential long-term impact on engine and fuel system health. None was found, and there seems to be little doubt that today's turbofans can be powered with biofuel in years to come.
Now, of course, a major challenge lies in finding ways in which such fuels can be produced in sufficient quantity at a competitive price. As the oil industry is not dependent on aviation, especially given the rising demand for other refinery products such as car fuel in the growing economies, airlines should not wait for their fuel suppliers to come up with the solution.
In the emergent paradigm, operators are not mere consumers, but are also responsible for sourcing and producing their own fuel. Fossil fuel may not run out soon, but it will become more expensive as living standards improve. Even if airlines choose to ignore the environmental argument - in the face of rising demand for greener transport in Europe, despite economic woes - they might still require alternative fuel to keep bills down.
Test flights have done their bit. Now, we need to see more biofuel sourcing projects, such as Lufthansa's engagement in camelina farming in Russia's Volga region or British Airways' support for a biofuel processing plant in east London. Biofuel works; let's get to work.
(This first appeared as the leading article in the 24 July issue of Flight International)