Proprietary technology, patented by Green Fuels Research (GFR), overcomes the key obstacle to use of fatty acid methyl esters (FAME) in aviation biofuel – low-temperature performance – and is expected to improve oxidative stability and provide relative flexibility with choice of feedstock. The fuel has been demonstrated at laboratory scale and meets or exceeds key ASTM requirements for jet fuel. It is now ready for pilot-plant scale-up, detailed characterization and commercialization.
Biodiesel based on FAME is well established as a fuel for road transport, heat and power, etc, and can be made from a wide range of feedstocks. When properly made, it meets ASTM requirements for road fuel.
Utility of such FAME for aviation fuel is, however, limited by its low-temperature properties, with gelling and waxing common at sub-zero temperatures. This is generally a result of a combination of a high proportion of saturated fatty acids in feedstock or a high proportion of longer-chain fatty acids. There is also the potential for oxidative instability with some biofuels.
Fractionation of a FAME mixture removes components responsible for low-temperature gelling as well as for oxidative instability. Processing of the resulting fractions saturates polyunsaturated fatty acids and shortens chain lengths yielding a blend of esters and alkanes with a high proportion of C9 alkane (nonane). Multiple fractions may be separated and blended to improve fuel properties. No significant waste stream is generated; by-products of the process generally have commercial value with benefits for process economics and likely fuel price point.
Fuel has been produced using this process, using Camelina sativa oil feedstock, in laboratory scale quantities. This fuel meets primary ASTM specifications for Jet-A fuel, as well as specifications for Jet-A1 and JP-8 fuels. A freeze point below the requirement for Jet-A1 suggests that this fuel will have good low-temperature properties.
The technology is the subject of US Patent 8,715,374, granted in May, 2014.
Feedstocks and economics
The feedstock used for laboratory demonstration of fuel, C. sativa oil, is unlikely to be the commercial choice. However, use of fractionation means that differences between feedstock species in lipid composition are relatively unlikely to affect final fuel composition and properties; rather this will influence yield as the proportion of initial triglyceride separated as a fuel fraction will vary. Several species of agricultural interest (soy, corn, canola, sunflower, and others) and Used Cooking Oil (UCO) should have good potential for commercial yields of fuel from this process; for sustainability reasons it is desirable that fuel can be made from feedstock outside the food chain and reported compositions of lipids from a number of algal species suggest this approach should also be suitable in the future once this feedstock becomes commercially viable.
In comparison to other technologies being used or developed for aviation biofuel, the GFR process is interesting for its integration potential with an existing biodiesel industry already generating tens of millions of litres of fuel every year. We believe this is a near-market approach to delivering realistic quantities of aviation biofuel with few technological obstacles and an attractive, real-world economic profile.
We are engaged in scale-up and pre-production process engineering, preparatory to extended testing with selected partners. This work is part-funded by the UK Department for Environment and Climate Change. We are open to discussions with interested parties from the aviation, aerospace, biofuel and fuel supply-chain industries. For an initial discussion, feel free to contact firstname.lastname@example.org.