The global aviation industry has pledged itself to some challenging goals over the last few years, specifically in terms of decarbonisation. Airlines and governments are both working towards steep targets, such as net-zero carbon emissions by 2050. To achieve these goals, the industry has widely accepted that significant changes are required, and the subject of how aircraft are fuelled has become a primary concern.
By now, everyone has heard of Sustainable Aviation Fuel. SAF is consistently one of the top subjects searched for on Google in relevance to aviation, with latest research showing annual demand growing at a rate of approximately 65.7% over the next six years. While SAF still creates roughly the same amount of CO2 when burned, no further fossil fuels are extracted during creation, resulting in up to 100% CO2 absorption. However, a common misconception is that SAF consists of one single innovative fuel type - when actually, the term SAF covers a range of new innovations in both fuel manufacture and technology. But what options are available to those seeking to decarbonise? What alternatives are there, and what are the pros and cons of each? In this article, we list the latest options and innovations on the table, and ask - what are the most likely fuels of the future?
Biofuels are produced by the refinement of fats, oils and greases, or FOGs, and can reduce CO2 emissions by up to 80% during a full lifecycle. Initially trialled in 2008, biofuels are often thought of as the first generation of SAFs, but have since evolved into the use of Hydrotreated Esters and Fatty Acids, or HEFAs, and have been used in over 450,000 commercial flights worldwide. Evidence of collaboration between the aviation sector and other industries exist - such as obtaining used cooking oil from fast-food chains. Although SAF is currently limited to being blended by 50% with fossil fuels such as kerosene for aviation purposes (providing the financial advantage of not requiring a costly change in airport fuelling infrastructure), we are starting to see the first 100% SAF commercial flights taking place. Additionally, an improved version of this fuel called HEFA+ (or High Freeze Point HEFA) is currently in testing.
However, the use of biofuel currently presents a number of significant challenges. The first of these is cost, with SAF being typically up to four times more expensive than kerosine. As a result, airlines are not currently buying large amounts, which leads to the next problem - limited supply. Due to the lack of commitment by the industry, energy providers are producing far less SAF than is needed, with current production estimated to be less than 0.1% of global jet fuel consumption.
FT-SPK is created through the gasification of biomass, such as crop residues, animal waste, and forestry waste, or pretreated Municipal Solid Waste (MSW), such as paper, plastic, cardboard, and textiles. This process produces syngas, which is then further treated to create FT-SPK - a fuel which provides 85% - 95% greenhouse gas savings compared to conventional petroleum jet fuel, depending on the composition of the waste used in manufacture - for example, MSW containing higher plastic content may produce more CO2. Like HEFA biofuels, FT-SPK can currently be blended with traditional fuels up to 50%.
Despite this, biomass-derived fuel has a low energy density compared to fossil fuels, and requires significantly more volume to generate the same energy. Another method for producing FT-SPK called Power-to-Liquid (PtL) is being developed, which generates syngas from the electrolysis of water, promising to reduce carbon emissions by up to 99% - but currently, much more investment in renewable energy and carbon capture technology is required to account for the relatively huge amounts of renewable electricity required for production.
The creation of ATJ-SPK occurs via biochemical or thermochemical sugar and starch crop conversion to create either isobutanol or ethanol, which is then further processed to create jet fuel. Again, this fuel can currently be blended with traditional fuels up to 50%.
Unfortunately, most experts concede that ATJ fuels generate more greenhouse gas emissions than HEPA or FT-SPK fuels, as often the energy required and emissions generated through the creation of the initial alcohol catalysts are taken into account. This means that ATJ-SPK can only save up to 75% of CO2 emissions - significantly less than other fuel types. Sugarcane-based fuels are thought to be more efficient and produce less emissions than maize-based alternatives.
Additionally, flue gases are now being looked at as potentially helpful and value-adding contributors to the creation of ATJ-SPK, but this theory is yet to be thoroughly investigated.
Farnesene is a less commonly known type of sugar-based crop alcohol which can be hydrotreated to create farnesane, which can then be used in the creation of jet fuel. Farnesane has a higher energy density than other alcohols, and is commonly used at a blend ratio of only 10% with traditional fuels.
More than half of the greenhouse gases created by this fuel type comes from crop cultivation and processing, but this could potentially be decreased using renewable energy sources. But the typical GHG reduction on traditional fuels currently sits at up to 75%, in line with other alcohol-based fuels.
No matter which type of fuel is chosen, one thing is certain in all cases - all forms of SAF require considerably more investment and buy-in, from governments and industries alike. Not only do we need improvements in aircraft innovations, fuel distribution, energy production and beyond - but a change in methodology in how industries use their fuel resources is also required.
At i6, we believe one of the most effective approaches to decarbonisation is to digitalise the entire airport fuel supply chain. Our fuel management technology seamlessly connects the fuel supplier, fuel farm, into-plane operator and airline to track end-to-end fuel movements. This provides key stakeholders with detailed and real-time information with greater operational control and efficiency. For example, airlines using our e-fuelling technology, eHandshake®, benefit from accurate data transmission and optimised refuelling - resulting in average savings of up to 201KG CO2 with every long-haul flight.
Get in touch for more information about how you can digitise your fuelling operations and reduce carbon emissions.