In the accelerating push to decarbonise aviation and marine transport fuels, constraints around the sustained availability of fats and oils feedstocks are already emerging.

Recent breakthroughs in feedstock engineering technology from Australia presents a promising alternative pathway to reaching maximum scale in renewable aviation and marine fuels.

Phasing out fossil fuels (coal, gas and crude oil) is the major thrust in global efforts to reach net-zero emissions and limit global warming.  This ‘decarbonising’ transition already has significant momentum in the stationary energy sector, where coal and gas-fired power stations are making way for increasingly cost-competitive solar and wind powered electricity generation. Attention is now being directed to replacing the liquid fuels – gasoline, diesel and jet fuel – derived from crude oil (petroleum), that are the energy mainstay of the global transportation sector.  These non-renewable high-emission fuels are able to be replaced by switching to renewable fuels, such as biobased ethanol and diesels, or even to alternative energy systems, such as electrically-powered or hydrogen-fuelled vehicles.

But it’s a massive challenge – and has been well documented in the recent IEA report on The Role of Renewable Fuels in Decarbonizing Road Transport and the World Economic Forum report Clean Skies for Tomorrow: Sustainable Aviation Fuels as a Pathway to Net-Zero Aviation.  Essentially, over 5 billon tonnes of petroleum is used globally every year; around 100 million barrels a day. Replacing all of this with renewable liquid fuels would be a daunting, perhaps impossible, task.

Fortunately, around three-quarters of this demand is from the automobile sector where conversion to (renewable) electrical and hydrogen alternative energy systems are already providing a promising path to decarbonisation at scale.

Decarbonising the other two major transportation sectors – aviation and marine – presents significantly greater challenges.  For the foreseeable future, aircraft and ships will continue to have a heavy reliance on liquid fuels – and that’s where bio-based renewable fuels will likely play a major role in decarbonising these transport sectors.

The aviation industry has been introducing Sustainable Aviation Fuel (SAF) into its supply chains over the past decade. SAF, a form of renewable diesel, is a product that meets the appropriately demanding specifications of the aviation industry. Initially through regulatory pressure, demand has catalysed the development of this industry.

Marine fuels are starting to follow that lead, driven by new low-sulphur standards that are unlikely to be met by current bunker oil products. Renewable diesel offers a sustainable pathway to meeting these new industry standards.

From a ‘farm to fuel’ perspective, the best feedstocks for SAF and renewable diesel are triglyceride oils.  Several airlines have already conducted test flights and commercial flights using SAF (at up to 50% blend) produced from a range of oil feedstocks, such as used cooking oil (UCO), non-food oils (e.g. Carinata oil) and waste animal fats (e.g. tallow).

Neste from Finland, one of the pioneers in renewable diesel, have begun expanding their production facilities globally, whilst more recent entrants are emerging and consolidating, such as Alt-Air, Diamond Green Diesel, Next Renewables, Ryze Renewables, and Renewable Energy Group. The petroleum sector itself is now joining the fray, with announcements from global majors, such as BP, Total, and Eni, that they have begun migrating parts of their refinery operations across to renewable feedstocks, either by blending bio-based oils into their petroleum feedstocks for standard refining, or by conversion of refineries over to dedicated production of renewable diesel from bio-based feedstocks.

The transition is gaining momentum, and nowhere is this more evident than on the West Coast of the US.  In a recent edition of Digest Connect, Jim Lane catalogued several new renewable diesel projects, including petroleum refinery conversions announced by Phillips66, Global Clean Energy, and Marathon Oil. These projects have been spurred on by strategic policy directions to move to 100% renewable fuels, signalled initially by California, and now being followed by neighbouring states.

These entry projects are being established on currently available oil feedstocks that are either unsuitable for food use (UCO, tallow, Carinata) or are traded food oils (such as palm, canola and soy). But the big question is – Can these feedstocks be expanded sufficiently to enable the full-scale transition to renewable fuel at global level?

Aviation fuel consumption has been running at around 300 million tonnes (96 billion gallons) per annum and is predicted to rise to top 520 million tonnes by 2050. And there’s at least another 300 million tonnes needed for marine fuel.  That’s a total market demand of over 800 million tonnes of fuel; a whole lot more than the combined 20 million tonnes of UCO and tallow that are currently generated each year, and several times the total amount of oils that are harvested from all of our current oil crops (including those oils used to meet food demand). It’s clear that expansion of renewable diesel production is heading for a looming fats and oil feedstock shortage in the decade ahead.

Supplies of UCO have already tightened significantly during COVID as a result of the widespread closures in the food service sector, impacting feedstock access in the production of renewable diesel for the current producers. This is hopefully a temporary disruption in feedstock supply, but it does serve as a timely portent of the constraints to expansion that will occur once the limited available supplies of these preferred feedstocks are exhausted in the medium-term. It points to the importance of developing new, more-scalable feedstocks to underpin further expansion of renewable fuels to meet the goal of complete petroleum replacement.

So where might these dramatically increased supplies of fats and oils feedstocks come from? What solutions are emerging that can meet this extraordinary demand – sustainably, cost effectively, and with minimal to no land-use change?

One solution that could be a game-changer in addressing this looming supply gap has recently emerged from CSIRO labs in Australia.  Over the last few years, researchers there have been developing Biomass Oil technology that revolutionises the way that plants produce oil. Rather than producing oils where they are normally made in their seeds and fruits, Biomass Oil plants have been engineered to synthesise and accumulate large amounts of oil in their vegetative biomass.

Plant leaf cells normally store their carbon and energy as low value starch & sugars – but with the Biomass Oil technology they are switched into oil factories producing high energy density triglycerides. Using tobacco as a model plant, CSIRO researchers were able to engineer up to 33% oil in leaves and stems. At the concentrations already achieved, oil yields of 5-6 tonnes per hectare can be anticipated when deployed in a high biomass tobacco grown at high intensity, making it equivalent to oil palm in productivity.

The technology has since been demonstrated to work in leaf, stem and root tissues of a range of other biomass plants, including sugarcane, sorghum and potato. It redirects the allocation of renewable carbon within the plant and is expected to be broadly deployable across a wide range of plant species.

Biomass Oil production could be readily integrated into existing agricultural footprints. Deployment as dedicated rotational oil biomass crops, or as valuable coproduct in the crop residue of food and feed crops, can complement rather than compete with acreage needed for food crops, breaking the food vs fuel nexus. The anticipated low ILUC (Indirect Land Use Change) score, combined with an inherently low carbon intensity, points to Biomass Oil having a highly favourable life-cycle analysis.

The step-change in oil productivity achieved through producing oil feedstocks directly in high biomass crops promises significantly lower cost-of-goods for renewable oils and fuels. Techno-economic modelling of Biomass Oil produced in sugarcane indicates that, at only 20% oil content, the production cost of diesel fuels was lower than the reported prices of renewable jet fuel produced from other oil crops and algae.

Biomass Oil is deployable globally through new crops customised for fit and performance in a range of agricultural regions – enabling a truly global supply chain network based on regionally sourced fuels, ultimately delivering uniform feedstock to industry specifications.

Addressing the challenges of accessing sufficient plant oil feedstocks to meet the escalating demand for renewable diesel and jet fuels present an extraordinary opportunity for innovations such as the Biomass Oil technology. Delivering increased plant oil productivity and profitability through the supply chain, while minimising displacement of current land use or farm practices, augers well for the impact that can be made through the deployment of this new approach.


Cameron Begley and Allan Green