Sustainable aviation fuel (SAF) is emerging as the primary method of reducing carbon emissions from the world’s enormous commercial aviation sector, with California emerging as the major testbed in North America. Although the potential is great, SAF supplies are limited and costs are high. Even in the best-case scenario, major regulatory reforms are required for this promising fuel to realize its full economic potential.
According to new study, an experimental plant-based jet fuel could improve engine performance and efficiency while eliminating aromatics, the pollution-causing molecules added to traditional fuels.
Researchers examined a jet fuel produced by Washington State University that is based on lignin, an organic polymer that makes plants stiff and woody, in a study published in the journal Fuel. The researchers studied fuel parameters crucial to jet engine operation, such as seal swell, density, efficiency, and emissions, using a variety of tests and projections. Their findings indicate that this renewable fuel might be used with other biofuels to completely replace petroleum-derived fuels.
“We noticed some surprising findings when we tested our lignin jet fuel,” said Bin Yang, a professor in WSU’s Department of Biological Systems Engineering and the study’s corresponding author. “We found that it not only had increased energy density and content but also could totally replace aromatics, which are a real problem for the aviation industry.”
The lignin-based fuel we tested complements existing sustainable aviation fuels by enhancing density and, maybe more importantly, ring-swelling capability of blends. These sustainable blends bestow better energy densities and specific energies without employing aromatics while addressing our material needs.
Bin Yang
“Aromatics are associated with increased soot emissions, as well as contrails, which are estimated to contribute more to the climate impact of aviation than carbon dioxide,” said Joshua Heyne, co-author, University of Dayton scientist, and current co-director of the joint WSU-Pacific Northwest National Laboratory Bioproducts Institute. “Aromatics are still utilized in fuel today because we do not have solutions to some of the challenges they solve: they give jet fuel with a density that other sustainable technologies do not. Most notable is their capacity to swell the O-rings needed to seal metal-to-metal junctions, which they accomplish exceptionally well.”
“We want to fly safely, sustainably, and with as little impact on human health as possible,” Heyne continued. “The question is, how can we achieve all of this in the most cost-effective way possible?”
To address environmental issues, EPA regulations normally limit both the total volume percent and the percentage of aromatics. However, aromatics are still employed since alternative options are not yet viable. “[Aromatics] deliver jet fuel with a density that other sustainable technologies do not,” said Joshua Heyne, co-author and current co-director of the WSU-Pacific Northwest National Laboratory Bioproducts Institute. “Most notable is their capacity to swell the O-rings required to seal metal-to-metal junctions, which they accomplish quite well,” he continued.
Yang invented a patented method for converting lignin from agricultural waste into bio-based lignin jet fuel. This type of sustainable fuel could assist the aviation sector in reducing its reliance on increasingly expensive fossil fuels while fulfilling greater environmental criteria.
The qualities of the WSU-developed lignin-based fuel “provide enormous prospects for better fuel performance, improved fuel efficiency, lower emissions, and lower prices,” the authors said in Fuel. “The fact that these compounds exhibit sealant volume swell comparable to aromatics opens the way to developing jet fuels with essentially no aromatics, extremely low emissions, and extremely strong performance characteristics.”
The features of lignin-based gasoline “provide enormous prospects for improved fuel performance, higher fuel economy, lower emissions, and cheaper prices,” according to the authors. The research “Lignin-based jet fuel and its blending impact with conventional jet fuel” explained how the unique fuel molecules exhibit sealant volume swell akin to aromatics. “While meeting our material requirements, these sustainable blends give better energy densities and specific energies without the use of aromatics,” Heyne explained.
“The lignin-based fuel we tested complements existing sustainable aviation fuels by enhancing density and, maybe more importantly, ring-swelling capability of blends,” Heyne explained. “These sustainable blends bestow better energy densities and specific energies without employing aromatics while addressing our material needs.”
“This process creates a cleaner, more energy-dense fuel,” Yang added. “That’s exactly what sustainable aviation fuels need for the future.”
