According to Splash 247 columnist Pierre Aury, the IMO’s decision to delay approval of its Net Zero Framework (NZF) gives the shipping sector a moment to clarify one of its biggest unknowns: what exactly counts as a renewable marine fuel.
Between the EU ETS, which puts a price on emissions, and FuelEU Maritime, which limits well-to-wake GHG intensity and requires cold ironing in port, shipowners now face strong pressure to move away from fossil fuels. When adopted, the NZF is expected to push the same shift globally.
What is a renewable fuel?
Aury notes that it’s any fuel derived from sources that naturally regenerate. In practice, regulators focus on biofuels and e-fuels, not on raw biomass like wood, which is impractical for shipping.
Biofuels: Three Generations
First-generation biofuels come from crops such as corn, sugarcane or rapeseed. They are widely used but raise concerns over land use and competition with food production.
Second-generation or advanced biofuels use waste, residues or lignocellulosic material, including used cooking oil or HVO. They offer better sustainability profiles but remain limited by available feedstock.
Third-generation biofuels, such as algae-based fuels, could avoid land-use conflict and scale more easily, but they are still experimental and costly.
E-fuels: Synthetic, Low-Carbon… and Expensive
E-fuels, also called synthetic fuels, combine green hydrogen (from renewable-powered electrolysis) with captured CO₂ to produce e-methanol, e-diesel, e-methane or e-ammonia. When both inputs are renewable or biogenic, these fuels can approach carbon neutrality. However, they are extremely energy-intensive and remain prohibitively expensive.
Aury stresses the distinction: green indicates renewable-powered hydrogen, blue refers to fossil-derived hydrogen paired with carbon capture.
A Note on Ammonia
Aury is blunt on one topic: despite industry excitement, ammonia “should not be considered a fuel for shipping” due to its safety risks.
Reality Check
Even with rapid progress, Aury concludes that no alternative fuel (bio-based or synthetic) can be deployed at the necessary scale to fully decarbonise global shipping by 2050. The technology is advancing, but the timeline is unforgiving.
