Air traffic has been steadily increasing for the last years. Moreover, fuel availability at a reasonable cost seems more and more uncertain. Climate change implies that greenhouse gases emissions should be reduced. In this context, the search for new alternative fuels for aircraft seems to be a promising solution.
Nevertheless, aeronautic represents a very specific transportation mode, due to its usage (short range, middle range, long range with the same fuel, worldwide distribution of the fuel…) and its compulsory security constraints.
In the first part of the European project ALFA-BIRD (Alternative Fuels and Biofuels for Aircraft development - FP7), a selection of the best candidates to become the fuels for the future of aircraft has been done. The selection process was very complex, due to multiple criteria (physical properties, economical issued, environmental issues…). A first matrix of 12 blends has been defined including: FSJF (Fully Synthetic Jet Fuel), FT-SPK (Fischer-Tropsch Synthetic Paraffinic Kerosene), Naphthenic cut, HVO (Hydrotreated Vegetable Oils), hexanol, furane and FAE (Fatty Acid Esters) in different amounts.
The FSJF consists of 50% FT-SPK and 50% of severely hydrogenated coal tar kerosene. FT-SPK and HVO are paraffinic compounds. FT-SPK fuels are well known products and a huge work has already been done to certify this product, leading to ASTM D7566. Moreover, there is a strong potential in term of availability due to multiple sources (Biomass, Coal, Gas, Waste). HVO displays chemical composition and physical properties close to FT-SPK ones, but their certification for aircraft use is still under discussion in May 2011 and could lead to a standardization before the end of the year. The naphthenic compounds represent products that come from direct liquefaction/pyrolysis of coal or biomass. Concerning the oxygenated compounds, the study of their potential use in aeronautics is very original and can be considered as a long-term view.
This first fuel matrix of 12 blends were evaluated following the standard jet fuel characterization. Thanks to this first study, 4 fuels were pointed out : FSJF, FT-SPK, a blend of FT-SPK and 50% naphthenic cut, and a blend of FT-SPK and 20% hexanol. This fuel matrix allows evaluating the potential of several chemical families: paraffinic, naphthenic and oxygenated compounds. This is also representative of a short, middle, and long term views. These 4 fuels will be deeply evaluated in term of combustion, material compatibility, stability during the second part of the ALFA-BIRD project.