Queensland researchers have been mixing waste from essential oil production with fuel, and found they can still achieve similar performance.

The production of orange, tea tree, eucalyptus and other essential oils relies on therapeutic grade products, so there is a substantial volume of low-value waste oil sitting unused.

QUT researchers have tested a range of waste oils for performance and emissions as a 10 per cent oil/90per cent diesel blend in a 6-cylinder, 5.9 litre diesel engine.

Essential oil blends produced almost the same power as neat diesel, with a slight increase in fuel consumption.

“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,” QUT PhD researcher Ashrafur Rahman said.

“Orange, eucalyptus and tea tree are either native or grown extensively in Australia for essential oil production.

“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.”

A report on the tests has been published in the journal Energies.