The role of certification in promoting the credibility of SAF and alternative marine fuels, with a special focus on the ISCC Credit Transfer System.

13 May 2025, published in Decarbonisation Technology

The global push for decarbonisation has placed significant pressure on ‘hard-to-abate’ sectors and major contributors to greenhouse gas (GHG) emissions, such as aviation and maritime transport. International and national climate goals targeting net-zero emissions by 2050 and voluntary programmes such as the Science Based Targets initiative (SBTi) are intensifying the need for drastic reductions in carbon footprints. Given that direct electrification poses challenges within these sectors, sustainable aviation fuels (SAF) and alternative marine fuels (AMF) present essential and non-negotiable options for achieving ambitious climate targets.

SAF is a renewable, non-fossil-derived fuel from biomass, waste oils, and fats, or e-fuel generated using renewable electricity, which can reduce emissions by up to 80% compared to conventional jet fuel (The University of Manchester, 2023). SAF’s chemical and physical properties are nearly identical to those of traditional jet fuel. This compatibility allows SAF to be mixed with conventional fuels in varying proportions, utilise the same supply infrastructure, and require no modifications to aircraft or engines, making it a ‘drop-in’ fuel technology. To ensure technical and safety standards, SAF must be produced according to one of the ASTM-approved methods (ASTM, 2023), the most widely used of which is hydroprocessed esters and fatty acids (HEFA), converting waste oils and fats into SAF. Another rising process is alcohol-to-jet (AtJ), where alcohols such as ethanol and isobutanol are transformed into SAF. Drop-in AMFs include biofuels, e-fuels, and liquefied biogas (Bio-LNG). In contrast with SAF, non-drop-in AMFs, such as methanol, ammonia, and hydrogen, also play a crucial role in the sector. While these non-drop-in fuels offer greater long-term sustainability benefits, they involve significant investment in new technologies.