Safran on the biofuel trail
Aviation is responsible for around 2% of global CO2 emissions associated with human activities, and this figure is rising as traffic increases. It is for this reason that numerous aviation industry players are seeking to reduce the sector's environmental impact.. The primary objective is to halt the rise in CO2 emissions by 2020 and then to reduce them by 50% by 2050. "It is clear that these objectives can only be met via a package of technological solutions relating to engines and aircraft, as well as the optimization of air traffic", explains Nicolas Jeuland, Safran's fuels of the future expert. "Sustainable alternative fuels are considered to represent one of the key factors in meeting this goal." The Group is thus working actively with its partners on the development of less polluting alternative fuels, within the context of the Air Transport Action Group and the Committee on aviation environmental protection.
A biofuel / kerosene mix
Four types of biofuel (see box) are certified for blending with kerosene. The biofuels in question require no adaption to engines and each of them has demonstrated perfect compatibility with all materials and equipment via the certification process. The blend proportions differ depending on the processes used: 10% farnesane (see box) for 90% kerosene, for example, or up to 50% biofuel with the HEFA technique. "It isn't feasible today to develop engines dedicated to a single type of alternative fuel because it has to be possible to refuel aircraft all over the world", specifies Nicolas Jeuland, Safran's fuels of the future expert. The so-called "drop-in1" fuel blend thus has a major role to play today in reducing CO2 emissions in the aviation sector."
Safran has been testing alternative fuels in its engines since 2007. Dozens of in-flight tests have been conducted on the Toulouse – Paris route using a farnesane and kerosene mixture on Airbus A321 aircraft fitted withCFM56 engines operated by Air France-KLM, within the context of the Lab' Line for the Future project supported by the DGAC (French Department for Civil Aviation). "Globally, it is estimated that some 2,500 commercial flights have taken place over the past five years using alternative fuels of various types", continues Nicolas Jeuland.
Economic and ecological stakes
Large-scale recourse to these alternative fuels is nevertheless governed by the principle of economic sense as well as genuine ecological benefits. Thus, a high-output production process may raise environmental issues if it involves using coal or non-sustainable crops (this is mostly the case for palm oil, for example). "A number of other factors also come into play, such as the fact that, due to their chemical composition, some alternative fuels deliver an additional environmental benefit by reducing turbine output particle emissions", adds Nicolas Jeuland.
Safran is thus seeking to evaluate the strengths and weaknesses of each of these biofuel processes and validate their compatibility with the technologies in question: "The challenge is to identify which one of the existing solutions will be economically viable and the most environmentally friendly, be it in terms of the raw materials required, the production methods employed or their use", concludes the expert.
1 A "drop-in" fuel is one that can be used as a partial or complete substitute for conventional kerosene with no operational impact (no changes required to infrastructures, particularly airports) or changes required to aircraft or engines, either existing or under development.
Four processes for the production of alternative fuels
There are currently four main production processes for fuels certified for aviation use, based on plants derived from non-food crops, leading to a reduction in greenhouse gas emissions compared to the traditional use of kerosene.
• The Fischer-Tropsch process produces fuel from biomass: lignocellulose (straw, forestry residues, etc.), from natural gas or coal via a gasification step. Result: a reduction in greenhouse gas emissions of up to 90%, depending on the biomass used.
• The HEFA (Hydroprocessed Esters and Fatty Acids) process uses the oils extracted from oil-containing plants and microalgae. Result: reduction in greenhouse gas emissions of up to 60%.
• The DSHC (Direct Sugar to Hydrocarbons) process concerns the production of farnesane, a substance derived from the biological transformation of sugar into a chemical compound called farnesene. Once hydrogenated, this compound can be directly incorporated into a fuel such as kerosene to the tune of 10%. Result: a reduction in greenhouse gas emissions of between 70 and 80% depending on the sugar-based raw material used.
• The Alcohol to Jet refining process is used to convert sugars into isobutanol, and then aviation fuel. Result: reduction in greenhouse gas emissions of up to 60%.