Jets to be fuelled by lemons

Dr Claudia Vickers, from the University of Queensland’s (UQ) Australian Institute for Bioengineering and Nanotechnology, hopes to use a chemical found in lemons and other citrus fruit to make renewable jet fuel.

Dr Claudia Vickers says limonene one day could be a renewable, clean aviation fuel. Photo: David Sproule.

Dr Vickers explained that the volatile chemical limonene, which contributes to the smell of citrus fruits, “was first identified in turpentine oil in the late 1800s and is now used as a flavour and fragrance in foods, household cleaning products and perfumes”.

As well as holding promise as an anticancer agent, the chemical is also an ideal jet fuel component. In fact, limonene extracted from citrus peel had been successfully used in demonstration flights in the past. “However, large-scale limonene production from citrus peel is impractical,” Dr Vickers said.

That’s why Dr Vickers is modifying baker’s yeast to produce a synthetic form of the chemical; a process which should “provide a route to much greater yields of limonene which are easier to extract”, she said.

At present yields are not high enough to be commercially viable, but Dr Vickers plans to further modify the yeast to improve this. Furthermore, the same technology could be used to make a variety of other sustainable products from limonene, including rubbers, plastics and paints.

Dr Vickers recently received a UQ Foundation Research Excellence Award worth $80,000 for her work with lemons and yeast. UQ Deputy Vice-Chancellor (Research) Professor Max Lu congratulated her during the award ceremony, noting, “Chemicals derived from yeast can play a role in futureproofing the Queensland economy by capturing part of the $2 trillion global chemical market”.

Her research into synthetic limonene builds on earlier Queensland Government-funded research which demonstrated that sucrose from sugarcane is one of the best biofuel feedstocks available in the state.

Dr Vickers noted, “Alternative energy sources … are unlikely ever to replace high-energy density fuels such as jet fuel.” Green chemicals, however, have relatively high prospects, particularly “as the amount of easily extractable fossil fuels decreases and the demand for alternatives to petrochemicals increases”, she said.

A United States Department of Agriculture report predicts that green chemicals produced using biomass will represent 22% of the chemical market by 2025.