You can be forgiven for getting confused over biofuels - there are so many feedstock-to-fuel pathways under development that it is hard to keep them straight.
But one thing has been common across all the test and demo flights conducted so far, by manufacturers, the military and airlines - they have been limited to 50% blends of biofuel and conventional jet fuel.
All photos: ARA/NRC
Now Canada's National Research Council (NRC) has flown a Dassault Falcon 20 bizjet (above) burning 100% unblended biofuel in its two* GE CF700-2D2 engines. The fuel, called ReadiJet, has been developed by Applied Research Associates (ARA) and Chevron Lummus Global with funding support from the US Air Force Research Laboratory.
The hour-long flight over Ottawa on Oct 29 used biofuel produced from carinata, an industrial oilseed crop, supplied by Canadian company Agrisoma Biosciences. A member of the mustard family, carinata is inedible - it's a laxative and tastes bad, so it can't be used in food, says ARA, but it can be grown on fallow land in hotter, drier climates.
What's important about this flight is the 100% biofuel bit. So far, synthetic jet fuels approved for use in aircraft - produced from biomass either via the Fischer-Tropsch process or by hydroprocessing - are limited to a maximum 50% blend because they are not exactly the same as conventional jet fuel.
Fischer-Tropsch and so-called "hydroprocessed esters and fatty acids" (HEFA) pathways produce synthetic paraffinic kerosenes (SPK) that have only straight-chain hydrocarbons. ARA's ReadiJet also contains the cycloparaffins and aromatics that present in petroleum-based jet fuel. This allows it to be used unblended, as the NRC flight demonstrated.
ARA hopes to get approval for its fuel to be used in aircraft by the end of 2013. Advantages claimed for the company"s "catalytic hydrothermolysis" process are that it requires only a small production footprint and that the capital and operating costs for a biorefinery will be lower than for HEFA SPK, and more competitive with conventional jet fuel.
Environmentally, ARA says its process reduces the amount of hydrogen needed, and therefore the carbon dioxide generated, during production. And 100% biofuel, versus a 50% blend, will maximize the life-cycle reduction in greenhouse-gas emissions that comes with using biomass as the feedstock. For the Ottawa test flight, an NRC Lockheed T-33 (above) flew behind the Falcon to measure airborne emissions generated by the biofuel.
*NOTE - Edited to correct to reflect that both of the Falcon engines burned 100% biofuel