Synthetic jet fuel blends receive final stamp of approval and pave the way for jet biofuel certification
A USAF B-52 carries out a Fischer-Tropsch test flight in 2006, in which two of the aircraft's eight engines ran on a natural gas-based FT fuel blend
Thu 13 Aug 2009 – The ASTM International Committee on Petroleum Products and Lubricants has formally adopted a new specification that will enable the use of synthetic fuels in commercial aviation. The specification, which had been provisionally called DXXXX, has a new number, D7566, and will sit alongside the current D1655 conventional jet fuel standard. Initially, D7566 only specifies up to 50/50 blends of synthetic fuel produced from the Fischer-Tropsch (FT) process, although this includes FT fuels made from renewable biomass-to-liquid (BTL) sources. However, the specification is to be structured, via annexes, to accommodate different classes of alternative fuels and approval for bio-synthetic paraffinic kerosene (Bio-SPK) is anticipated before the end of next year.
The specification describes the fuel properties and criteria necessary to control the manufacture and quality of these fuels for drop-in aviation use.
The relatively fast approval of the use of synthetic jet fuel blends in commercial, private and military aviation has been welcomed by representatives of the US aviation industry.
“This action by ASTM occurs a mere two years since the first formal synthetic paraffinic kerosene (SPK) tests by the US Air Force of gas-to-liquid (GTL) fuel on a B-52 aircraft. It should eliminate any doubt among investors and fuel suppliers that aviation can act in a unified and timely manner to qualify new fuels that meet our exacting requirements,” commented Richard Altman, Executive Director of the Commercial Aviation Alternative Fuels Initiative (CAAFI), a collaborative effort of airlines, engine and airframe manufacturers, airports, universities, the FAA and others to advance the production and acceptance of alternative aviation fuels.
The President and CEO of the Air Transport Association of America, James C. May, said: “The unanimous passage of this specification is significant for all consumers of jet fuel. For the airline industry specifically, this brings us one step closer to our aim of widespread production of cleaner, alternative fuels that will help the industry meet its environmental goals while enhancing the security and competitiveness of its energy supply.”
The Aerospace Industries Association (AIA) said the approval of FT-SPK would help pave the way for the approval of additional renewable fuels, such as Bio-SPKs. “This is another step forward in our industry’s efforts to reduce our carbon footprint and secure energy independence,” said AIA President and CEO Marion Blakey.
The use of Bio-SPK as a technical terminology for jet biofuels has been recently championed by Boeing to replace the previously accepted hydrotreated renewable jet (HRJ) description, and appears to be gaining industry acceptance.
Dr James Kinder, Senior Engineer at Boeing Commercial Airplanes, says SPK is consistent with the terminology used in Annex A1 of the new ASTM specification, even though neither Bio-SPK or HRJ have been officially defined.
“In the research report presented to the ASTM community supporting the use of Bio-SPK in aviation, we included a detailed description of the process to make Bio-SPK from triglycerides as well as the similarity of the FT-SPK and Bio-SPK fuels,” he told GreenAir Online.
“My concern with using the term HRJ is that hydroprocessing is a generic chemical process term that describes the reaction of a material with hydrogen in the presence of a catalyst and it may lead to some confusion in describing the fuel. For example, jet fuel produced by using a starting material that was produced from an FT process also uses hydroprocessing to make jet fuel. The FT process only makes the starting material (olefins or long chain paraffins). The backend process (hydroprocessing) followed by separation makes the jet fuel. If biomass is used in the gasification process then BTL could be considered HRJ.
“In addition, I’m aware of at least three processes being promoted that could be considered HRJ that don’t start with triglycerides and some of these processes produce aromatic compounds which are not paraffins. Therefore, Bio-SPK is more specific in describing the type of paraffinic fuels that are produced from a triglyceride than HRJ and it is consistent with the terminology that is contained in the new specification.”