Could jet fuel grow on trees? ANU finds promise in Australian gum-leaf

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Eucalyptus oils from certain gum tree species could be refined to make high energy jet fuel, an ANU study has found.

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Oil from the leaves of the iconic Australian native gum tree could be used to make a renewable jet fuel of the future, according to the results of an international study being led by the Australian National University.

The main goal of the ANU led study, which has been conducted in collaboration with US-based Oak Ridge National Laboratory, University of Tennessee and University of Florida, is to find an alternative to fossil fuels for powering modern jet aircraft.

lemon-scented-gum

According to ANU lead researcher, Carsten Kulheim, this goal has been difficult to achieve, due to the high energy density required.

“Renewable ethanol and biodiesel might be okay for the family SUV, but they just don’t have a high enough energy density to be used in the aviation industry,” Dr Kulheim said.

The international study, which has been published in Trends in Biotechnology, hopes to overcome this problem using a component of eucalyptus oil called monoterpenes, which are contained in the leaves of certain species of gum tree.

Certain monoterpenes commonly found in eucalyptus oils such as pinene and limonene, can be refined through a catalytic process, resulting in a fuel with energy densities suitable for jet fuel, the study has found.

“If we could plant 20 million hectares of eucalyptus species worldwide, which is currently the same amount that is planted for pulp and paper, we would be able to produce enough jet fuel for 5 per cent of the aviation industry,” said Dr Kulheim.

ah1p1841 Carston Kulheim
ANU’s Carsten Kulheim

And while this would initially be more expensive than fossil fuels to make on a mass scale, it would produce significantly less net carbon emissions.

The study’s main focus is to find a way to boost production of monoterpenes to obtain industrial scales of jet fuel, using genetic analysis, advanced molecular breeding, genetic engineering and improvements to harvesting/processing of the oils.

Co-researcher David Kainer, a PhD candidate at the ANU Research School of Biology, said the knowledge gained through the research could be used to enhance yield through breeding techniques and genetic selection.

“We can double, perhaps even triple, the yield that we can get per hectare to make a bigger dent in the aviation fuel industry,” he said.

“We’re looking for species that have the right type of oil and in addition to that, since the oil is in the leaves, they need to grow a lot of leaves in a short amount of time.

“Eucalyptus plantations globally produce up to 200kg of oil per hectare per year, but by selecting the best genetic stock they could produce more than 500kg of oil per hectare,” Kainer said.

“We can plant these trees on marginal lands that have low rainfall, and we can also plant them in agricultural systems that have salinity problems and help them defeat that problem.”

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11 Comments
  1. john.boland 2 years ago

    tell us what species without having to access the article. some of us know a lot about native plants and this would help.

  2. Gordon 2 years ago

    Mallees (which describes the form of the tree, rather than a species) – I don’t know which particular species though.
    This idea has been around for quite a while:
    http://oilprice.com/Latest-Energy-News/World-News/Virgin-Australia-To-Experiment-With-Eucalyptus-Oil-As-Biofuel.html

    http://www.abc.net.au/news/2014-05-21/mallee-tree-oil-could-be-used-for-jet-fuel/5467680

  3. Farmer Dave 2 years ago

    Twenty million hectares providing enough jet fuel for 5% of current demand? This does not look like a business as usual solution to me! We should not be surprised at the low yield per hectare per year, because the fundamental process, photosynthesis, while extremely important, is not very efficient in energy terms.

    I don’t want to denigrate the work reported on here, though. Even if the aviation industry as we now know it does not survive the phase-out of fossil fuels, we still would like to have emergency services such as rescue helicopters, and we need to fuel such essential services with fuels other than fossil fuels. Work such as this is important, but will not enable business as usual without fossil fuels.

    • A Wall 2 years ago

      Photosynthesis is highly efficient, that’s not the problem. The problem is that aviation uses such an incredibly huge amount of energy.

      • Farmer Dave 2 years ago

        I agree that aviation uses a lot of energy. However, I think we have differing definitions of “highly efficient”. According to the references I found, photosynthesis converts from 3% to 6% of the incident solar radiation to chemical energy, which does not fit my definition of efficient.

        This low efficiency is the reason why Miles Harding’s comment about scale is so important.

        • A Wall 2 years ago

          Yes, but I think you’re comparing it to a solar PV panel, which only produces electricity. By comparison, a tree is a self-assembling, self-replicating solar to chemical storage facility. That is a fundamental difference in kind.

          There is a larger question though — given the length of time that evolution has been optimising photosynthesis, is it even possible for humans to design/build systems that have a better whole-system efficiency in converting sunlight into stored energy? I don’t think we can answer this yet.

          I totally agree with Miles’ comment. I can’t see a way to sustainably fly aircraft at anything like current scale (unless we make some fundamental new advances in physics)

    • Chris Fraser 2 years ago

      It would be interesting to know just how the aviation industry thrives on business commuting at 2016 levels. This would be a much larger proportion than rescue helicopter miles.if we could just improve other low carbon technologies such as teleconferencing and remove some business trips, the energy provided through the new biofuel would rise as a proportion of total fuel usage.Climate denialists could use such well-made points to fortify their assertion that efforts to decarbonise the economy are futile. But for others the challenge has been clearly set.

  4. Ian 2 years ago

    Of all the renewable energy ideas this has got to be the fruit right at the tippy top of the tree overexposed and shrivelled. Plenty of low hanging fruit like solar PV, wind energy, public transport, high speed rail, and the like but then again, what seems silly like solar bikeways or highways may actually be the technology of the future. The degradation of natural areas will probably make tourist airtravel pointless anyway, who would want to travel across the world to see gumtree plantations on ‘marginal lands’.

  5. Miles Harding 2 years ago

    There’s that little problem of scale again.

    While it’s refreshing to see a proposal that acknowledges the scale of the airliner problem, I suspect that there are no fixes apart from actually stopping flying.

    A couple of years back, I was at a talk on bio-jet fuel that was promoting algae as the solution. The metric from that talk was 200Ha of intensely farmed algae could produce enough fuel for one airliner, presumably somewhere sunny and warm. This sounded pretty impressive whether of not it’s exactly correct isn’t really important here.

    The problem is that the world currently has about 30,000 airliners in regular service, so to fuel all of them with algae bio-jet would require 6MHa, or a strip of land 6000km long x 10km wide. We’d definitely be able to see those jet fuel farms from space.

    Back to the forest…
    Lets do a back-calculation to see how much eucalypt forest is needed for a single airliner. The fleet size the story talks of is about 1500 aircraft, so each one will be responsible for consuming about 13,000Ha of forest produced oil. This is still a lot of, even marginal, land to divert to a single use. I can’t see much relief from pulp and paper demands, particularly as packaging will have to move from oil based plastics to renewable paper based packaging at the same time as the avaiation industry is being forced off kerosene.
    This will also occur at the same time that trucking and shipping will be scrambling away from oil, so this sector will be competing for the same resources.

    My read of the scaling limits for biofuels is that it is probably possible to produce enough to make specialised use of them for areas that are vital to society, such as farming or some transport. Possibly, this could also include some aviation, but even 5% of the current fleet is likely a stretch.

    Food production may also impinge on biofuels, as our overpopulated world struggles to feed itself in an environment of diminishing agricultural resources. Food production is looking to be impacted from many sides, including topsoil loss, nutrient depletion and aquifer depletion. Much of our fertilisers are either mined or produced from hydrocarbons, which will make them less available as the cnetury progresses.

    It’s hard to see aviation being high in the priorities of a starving world.

  6. Coley 2 years ago

    “We can plant these trees on marginal lands that have low rainfall, and we can also plant them in agricultural systems that have salinity problems and help them defeat that problem.”
    The salinity bit puzzles me? Do gums like saline conditions?
    However any projects that involves the planting of more trees rather than the rampant deforestation we currently encourage gets me vote.

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