Essential oils with plants

Sweet essential oils could improve scent of diesel exhaust, study shows

Image credit: Dreamstime

An Australian study suggests that waste essential oils could be blended with diesel for a less offensive-smelling blend which performs just as well as pure diesel.

In many countries, diesel- and petrol-fuelled cars are on their way out for good; these cars will be phased out by 2040 in the UK and France, and in China by an unspecified date. Historically, diesel cars have been celebrated for their fuel economy, although the diesel emissions scandal – which engulfed Volkswagen and numerous other automakers – has tarnished their reputation as environmentally responsible alternatives to petrol cars.

In addition to the health concerns surrounding their higher-than-measured emissions of nitrous oxide (NOx) and compounds in their carcinogenic exhausts, the pungent scent of the exhaust has been criticised for becoming the dominant smell in cities like London.

According to research conducted by Ashrafur Rahman, a PhD student at Queensland University of Technology, this smell could be reduced by combining diesel with waste essential oils. According to Rahamn, only “therapeutic-grade” essential oil – concentrated oil containing volatile aroma from the non-fatty parts of plants – can be used for aromatherapy, perfume and cosmetics.

This means that a substantial volume of lower-grade oil is left over, unable to be used.

Rahman tried combining the leftover, sweet-scented orange, tea tree and eucalyptus oils with diesel in different proportions and poured the blend into a 5.9l diesel engine and tested each of the essential oil blends for performance and emissions. Rahman found that a blend of 10 per cent essential oil mixed with 90 per cent diesel performed nearly as well as pure diesel.

“Our tests found essential oil blends produced almost the same power as neat diesel with a slight increase in fuel consumption,” said Rahman. “Diesel particulate emissions, which are dangerous to human health, were lower than pure diesel, but nitrogen oxide emissions, a precursor to photochemical smog, were slightly higher.”

Rahman commented that the abundant supplies of waste essential oil in Australia meant that the introduction of less unpleasant diesel exhaust could be a possibility.

“Orange, eucalyptus and tea tree are either native or grown extensively in Australia for essential oil production,” he said. “We see the main use for an essential oil/diesel blend would be in the agricultural sector, especially in the vehicles used by the producers of these oils.

“With further improvement of some key properties, essential oils could be used in all diesel vehicles.”

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