Sustainable aviation fuel has a feedstock problem. Everyone knows that there are not enough suitable wastes to provide all the fuel needed to decarbonise aviation. Recent announcements from oil companies in the US and Brazil show how companies in the Americas are turning to crops to plug the gap.
European politicians and regulators still think that importing evermore used cooking oil from China, plus incentives to use difficult to process agricultural wastes, will plug the gap until ‘e-fuels’ made from renewable hydrogen and captured carbon dioxide, are commercialised. They are also betting on reduced demand for raw materials from the road transport sector, due to the uptake of electric vehicles, thereby freeing volumes for SAF. However, there are several things wrong with this strategy, which is why companies are turning to virgin raw materials from agriculture. Bayer, Neste, BP and Petrobras have all made announcements recently about new initiatives for production of crop-based aviation fuels.
The International Civil Aviation Organization (ICAO) has approved all types of SAF for inclusion in its Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA) scheme. Agricultural products must be certified as coming from deforestation free land and GHG savings targets must be met. CORSIA applies worldwide of course, whereas the EU has imposed its own rules on flights in Europe.
Most types of biogenic oils are currently favoured as they are the easiest to process. They are hydrogenated to form HEFA (Hydroprocessed Esters and Fatty Acids) in an established process. The product can also be redirected to the biodiesel market if the demand from aviation is insufficient.
Other approved pathways include Fischer-Tropsch (FT), which can use agricultural waste biomass, and Alcohol-To-Jet (AtJ), via bioethanol. Methanol to jet has also been proven. All these pathways produce SAF that is significantly more expensive than conventional jet fuel. The price gap presents a large risk in commercialising such technology. That risk is increased by the tendency of the European Commission to row back on hard decisions when the cost impacts on the consumer are severe.
Processes using virgin and waste oils have the lowest technology and price risk, but they both have reputational issues. Airlines don’t like to be associated with the food v fuel debate. And some used cooking oil from China and Indonesia has been found to contain virgin palm oil. Although the EU is introducing a database to overcome fraud around wastes, it is not clear how effective it will be.
To get an indication of aviation fuels which are, or soon will be, on the market, it is instructive to look at certification data. The database of the leading sustainability certification scheme, ISCC, shows that the main raw materials listed on CORSIA certificates issued in the last six months, were wastes, with used cooking oil (133) in the lead followed by animal fats (38), and palm residues (22). Crops, including corn, sugarcane, soybeans and rapeseed were listed on 20 separate certificates, indicating significant interest in both vegetable/seed oil HEFA and alcohol-to-jet.
But what of e-SAF? There is a European mandate for this type of fuel, beginning in 2030. But with no commercial facilities under construction, operators are unlikely to be able to meet the mandate in time. In an interesting twist, producers are arguing that the mass of renewable hydrogen in other types of SAF should count towards the mandate. Hydrogen produced from water and renewable electricity is technically an approved e-fuel (or RFNBO - renewable fuel of non-biological origin) according to the Renewable Energy Directive. Hydrogen cannot be used on its own as jet fuel, but it is integral to the hydroprocessing of oils to make HEFA. Needless to say, objections have been raised to this argument.
These diverging developments reflect how difficult it is to predict the path to large scale uptake of sustainable aviation fuel. The Americas, by following CORSIA and allowing the development of crop based SAF, are taking a different route from Europe. Until a worldwide consensus emerges, investors are flying blind.
Published: 28 September 26
