Aeroplane flying over snowy city

Cycloalkanes could be the key to sustainable aviation fuel

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Scientists at Sandia National Laboratories in the United States have explored the properties of a molecule that could significantly reduce the aviation industry's carbon emissions.

Cycloalkanes are molecules composed of hydrogen and carbon atoms arranged in a ring structure using only single bonds. According to new research, they could be vital to the development of cleaner aviation fuel, as they might reduce the condensation trail formation and soot emissions caused by current fuel.

The Sandia team has published the findings of its investigation - made in collaboration with researchers at Los Alamos National Laboratory - in an article in Frontiers in Energy Research.

Currently, the aviation sector produces around 2.1 per cent of all human-induced carbon dioxide emissions.

Although the industry has been severely hit by the pandemic, it is nonetheless expected to make a full recovery in the next year and, by 2038, experts predict aviation will contribute 1.7 trillion dollars to the global GDP.

The growth in demand for aviation fuel over the next few decades will result in a worsening of the effects of climate change, so scientists are rallying to find solutions that will make the industry more sustainable.

“Unlike other forms of travel, such as cars and trucks, there is currently no foreseeable path to electrify the aviation sector,” said Sandia chemist Alexander Landera. “Therefore, mitigation efforts are necessary to decarbonise the aviation industry.”

To achieve this goal, the Sandia team has focused on reducing the aromatic content of aviation fuel by replacing it with cycloalkanes.

Aromatics are substances derived from refining crude oil. They are often used as a source of octane to increase the engine’s power and fuel efficiency. Traditionally, aromatics have been beneficial in fuel because they cause the O-rings in the engine to swell, an important function in maintaining engine seals and preventing fuel leaks.

However, aromatics also produce soot during combustion, which has a greenhouse effect and contributes to the heating of the Earth's atmosphere.

“Ideally, we would wish to remove all aromatics from fuel,” Landera said. “But if we can even replace a large portion of the aromatics with cycloalkanes, we find they make good candidates as far as their ability to cause O-ring swelling and their strong fuel properties.”

Cycloalkanes can also be produced from feedstock or renewable biological material, potentially making their production more sustainable.

Landera hopes that by building a database of these properties, his team's research will help pave the way for cycloalkanes’ inclusion in future aviation fuels and make sustainable aviation fuels a cost-effective reality.

Funded by the US Department of Energy’s Bioenergy Technologies Office, this research is part of Sandia’s overall mission to address the national and global security threats associated with the climate crisis. The laboratory has made significant discoveries in technologies related to this mission, including combustion research, solar thermal testing and wind farm technology.

“Climate change poses a threat to national and global security,” said Anthe George, senior manager of Sandia’s applied biosciences and engineering group. “Developing sustainable aviation fuel, with decreased carbon dioxide and soot emissions, will be pivotal to ongoing mitigation efforts against global warming.”

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