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USDA is making air travel more sustainable with soy fuel innovations

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Scientists at the USDA Agricultural Research Service in Peoria, Illinois, pioneered a way to turn soybean oil into a better biofuel for jet aircraft.

Fatty acids from soybean oil can be made into a number of industrial products normally made from petroleum, including fuel, inks, and paints. One of the attractions of herbal products is that they recycle carbon from the atmosphere. This makes plants a far more renewable resource than petroleum and other fossil fuels, which add carbon to the atmosphere when extracted from the earth and used.

However, soy aviation fuels developed to date contain inadequate amounts of “aromatic” compounds that give the fuel the desired density and help keep jet engine seals pliable and functioning properly. The current shortage of aromatics in soy jet fuel means less of it can be blended with conventional petroleum-derived jet fuels, said Ken Doll, research chemist at the ARS National Center for Agricultural Utilization Research in Peoria.

Biofuel admixtures are one of the aviation industry’s ways to reduce its “carbon footprint” or overall emissions of greenhouse gases, especially carbon dioxide (which amounted to 905 million tonnes in 2018).

One approach to making soy fuel involves using a noble metal called ruthenium to catalyze reactions that chemically change the structure and properties of the unsaturated fatty acids in the oil. The problem with this approach is that too few aromatic compounds are produced, noted Doll with the bio-oil research division at the ARS center.

To get around the problem, he and his ARS colleagues Bryan Moser and Gerhard Knothe replaced ruthenium with iridium as the main catalyst in a six-step process that they developed and received a patent in November.

In laboratory-scale experiments, applying the approach to high oleic soybean oil produced jet fuel formulations with 8 to 35 percent aromatics – a range that is compatible with conventional fuels and beyond what ruthenium-based processes can achieve.

The progress, about which the team recently reported in an online edition of the International Journal of Sustainable Engineering, opens the door to increased blending of bio and conventional aviation fuels as a measure to reduce emissions. The process also produces little or no naphthalene, a jet fuel component that emits soot when burned.

The researchers are now looking for an industrial partner to scale the process and further evaluate its commercial potential.

Her research also supports broader efforts by the ARS Center in Peoria to develop new value-added uses for agricultural raw materials or their waste by-products, as well as sustainable new methods of processing them. Ideally, for example, the iridium used to make soy fuel could be replaced or combined with an abundant catalyst like iron to cut costs, Doll said.

In addition to soy, other oilseed crops could be used, including inedible sources such as arable watercress. “We originally used soybean oil for its high quality, affordability and the existing refining processes. It is also a raw material that we have worked with in Peoria in the past,” added Doll. “But any oil that has significant oleic acid content would work.”

The efforts of the Peoria team also reflect the U.S. Department of Agriculture’s participation in the Sustainable Aviation Fuels Grand Challenge along with other federal agencies and stakeholders. The challenge is a multi-faceted government-wide commitment to produce 35 billion gallons of sustainable aviation fuel annually by 2050 using “home grown” and other renewable sources.

The Agricultural Research Service is the U.S. Department of Agriculture’s primary scientific in-house research agency. ARS focuses daily on solving agricultural problems affecting America. Every dollar invested in agricultural research results in an economic impact of $ 17.

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