The Partnership for Air Transportation Noise and Emission Reduction at MIT and RAND Corp.’s Environment, Energy, and Economic Development Program joined forces recently to conduct a study sponsored by the Federal Aviation Administration. The resulting report, “Near-Term Commercial Feasibility of Alternative Jet Fuels,” has brought to light some interesting conclusions.

One of the report’s key findings is that in the next decade, up to three alternative jet fuels could be available in commercial quantities: Jet A derived, from Canadian oil sands and Venezuela’s very heavy oils (VHOs); Fischer-Tropsch (FT) jet fuel produced from coal, a combination of coal, and biomass, or natural gas; and hydrotreated renewable jet (HRJ or biojet) produced by hydroprocessing renewable oils.

According to the report, “All three are or can easily and inexpensively be made fully compatible with current aircraft and fuel-delivery systems.”

In brief, “Canadian oil sands and Venezuelan VHOs have the largest potential of several hundred thousand b/d of jet fuel, but their use would result in increased GHG [greenhouse gas] emissions. The prospects for FT jet fuels depend crucially on construction of a few pioneer commercial plants in the next few years. Production of commercial quantities of HRJ depends on the availability of appropriate feedstocks at competitive prices.”

Five kinds of prospective jet fuels were assessed by the study: conventional petroleum fuels, unconventional petroleum fuels, FT synthetic fuels, fuels from renewable oils, and alcohols.

Viability was based on the following criteria:
• Compatibility with current systems (existing commercial aviation infrastructure, which includes fuel delivery and storage and the existing fleet of aircraft);
• Maturity of the fuel-production technology – the production potential of the fuel in the next decade (which was in some cases limited by resource constraints and in others by the maturity of the fuel production technology, which could limit the number of commercial plants that could be built over the next decade);
• Production costs;
• Environmental benefits (lifecycle GHG emissions and emissions affecting air quality); and
• Relative merit for aviation use (as certain fuels more be more appropriate for automotive applications than for aviation).

Included in the study findings is the observation that in the next decade, alternative fuels will be available to reduce aviation’s impact on climate, even though supplies are limited.

“Certain HRJ and FT fuels are able to reduce the GHG emissions from aviation,” the report says. “For HRJ to be effective in reducing GHG emissions, it must be produced from oils that do not incur land-use changes, either directly or indirectly, that cause a large release of other GHGs. This constraint places a severe limit on the amount of climate-friendly HRJ that can be produced within the next decade. For FT jet fuels to be effective agents for GHG reduction, they must be produced from biomass or a combination of coal and biomass. In the former case, the fuels will be expensive and demand extensive cultivation of biomass for inputs. In the latter case, capture and sequestration of plant-site carbon emissions would be required, but overall costs would be much less, as would biomass consumption. As with HRJ, the provision of biomass must not incur land-use changes, either directly or indirectly, that cause a large release of GHGs.”

Several recommendations resulted from the study’s findings. One is that measures designed to lower GHG emissions should not treat commercial aviation separately from other sectors. Another is that any measures designed to promote alternative fuel use in aviation should consider the potentially large GHG releases associated with land-use changes required for cultivating crops for producing biomass or renewable oils. And there has to be support for long-term fundamental research that targets creation of middle distillate fuels for use in ground transportation and aviation.

The complete study is available here

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