Thu 18 Dec 2008 – One of the major obstacles towards industry-wide adoption of non-conventional jet fuels has been the issue of certification. A meeting last week in Florida of ASTM International, which oversees the international standards and specifications for jet fuel, secured major progress towards a new framework that will soon lead to a new alternative fuels specification, provisionally called DXXXX, which will sit alongside the current D1655 conventional jet fuel specification. The creation of DXXXX is expected to speed up the approvals process and provide confidence to potential fuel producers.
Richard Altman, the Executive Director of the Commercial Aviation Alternative Fuels Initiative (CAAFI), called the outcome a huge step forward. “When we look back one day at the history of the development of alternative aviation fuels, this meeting will clearly have been a key event,” he told GreenAir Online.
Craig Fabian, Director of Technical Operations for the Air Transport Association of America, representing US airlines, said the session was “extremely positive” and that “great strides” had been made towards the adoption of the first generic alternative jet fuel blend.
The proposed new DXXXX specification – which is now targeted to be formally adopted at the next ASTM meeting in June 2009 – constructs a framework to enable the use of multiple alternative fuels, including both non-renewable and renewable blends, for aviation use, and targets complete interchangeability with D1655-specified conventional jet fuels. The specification describes the fuel properties and criteria necessary to control the manufacture and quality of these fuels.
“The framework, once adopted, will serve to allow multiple alternative fuels to happen, and to happen far more quickly,” says Altman.
DXXXX is being structured to accommodate different classes of alternative fuels in annexes (or appendices) to the specification. According to Mark Rumizen, Aviation Fuels Specialist with the Federal Aviation Administration (FAA) and a member of the CAAFI steering committee, each new class of fuel will be added upon completion of an evaluation process.
Rumizen says the ASTM aviation fuels subcommittee intends to add biofuels from hydroprocessing mechanisms, which ASTM is calling ‘hydroprocessed renewable jet’ (HRJ) fuels, as a specified blend percentage to DXXXX when the technical evaluation of these fuels is completed. “ASTM has established a separate task force to coordinate the evaluation of HRJ fuels and will work as expeditiously as possible to complete this task,” he adds.
Altman describes the biofuel blends that are being used in the Air New Zealand, Continental Airlines and Japan Airlines demonstration flights soon to take place as HRJ fuels. “DXXXX appendices for those biofuel types – contingent on the outcome of testing now in process and the resultant research reports – are targeted by CAAFI interests for approval as a blend within eighteen months to two years, assuming the DXXXX approval goes ahead as planned in June,” he says.
In the meantime, the initial annex of the DXXXX specification will include only a 50/50 blend of synthetic fuel produced from the Fischer-Tropsch (FT) process. Rumizen points out that this will include FT fuel made from renewable biomass sources, commonly referred to as BTL, or biomass-to-liquid. Required data to support that annex are already in hand. Those results were included in a technical report completed in September and adopted by the ASTM subcommittee last week.
“Our goal is to make sure certification is not the critical path to deployment of alternative fuels. This new specification framework serves to remove a key obstacle,” states Altman. “Building the facilities and ramping up production then becomes the key criteria.”
At the ASTM meeting, a revision was approved to D1655 that allows the use of synthetic FT coal-to-liquid (CTL) jet fuel from the SASOL refinery in South Africa. A semi-synthetic (i.e. blended) SASOL CTL fuel had been incorporated in the jet fuel specifications in 1999. “This approval was very limited, however, to a specific fuel formulation from a specific refinery, not a generic approval which we are working on now,” explains Rumizen. “Incorporation into the jet fuel specifications confirms that the SASOL fuel met the criteria of the spec and therefore is an approved jet fuel relative to certification.”
The use of synthetic fuels produced through the FT process, such as coal-to-liquid or gas-to-liquid, has come in for criticism because on a life-cycle basis they can emit even higher greenhouse gases than conventional jet fuels. The US Air Force, a major potential customer for alternative fuels, is mandated by law to ensure it only uses such fuels which do not exceed the GHG emissions of current oil-based fuels. Commercial airlines in the US have voluntarily agreed to follow similar lines.
Altman believes this obstacle can be overcome through carbon capture and blending CTL and BTL fuels (CBTL), citing a number of studies accomplished by major universities and government laboratories that have been made available to CAAFI’s environmental team (see graph below). He says CAAFI and its airline sponsors have seen the most active FT process interest largely from planned CBTL ventures in Ohio, Illinois and Mississippi that will use carbon capture technology.
In addition to the activities of its certification team, CAAFI’s environmental team is documenting and contributing to the full scope of life-cycle analysis (LCA) initiatives. According to Altman, the team is using unbiased US Government production assessment tools being developed by the US Air Force, the US Energy Department and the Environmental Production Agency, in concert with globally endorsed aircraft emissions predictions tools developed by the FAA in conjunction with ICAO, to establish a peer-reviewed, aviation-unique LCA methodology that users and purchasers can rely upon in making investment decisions globally.
“LCA case studies from UOP, Neste in Europe and other biofuel entities – all stakeholders in CAAFI’s environmental team – in addition to the FT providers, are included by the team to fine tune and bound the range of potential outcomes,” he adds.
Greenhouse gas emission rates for fuel production use (source: Princeton University studies, W. Harrison & R. Altman, March 2007)
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