Transitioning the global maritime sector will require new zero-emission fuels (ZEFs) and additional investments beyond the fuels themselves, including new technologies to retrofit vessels to run on ZEFs.
ZEFs include green ammonia, green hydrogen, e-methanol, and synthetic e-fuels produced from renewable sources of energy. E-methanol and synthetic fuels made with renewable electricity still release some carbon dioxide (CO2) when combusted, so, to produce net-zero emissions, some CO2 used to synthesize these fuels will also need to be captured from the atmosphere. While batteries are also a zero-emission option, their relatively low energy density makes them unsuitable for long distance shipping but can contribute to decarbonizing shorter domestic voyages.
As of 2024, the global share of ZEFs in shipping remained close to 0%. The uptake of green ammonia and green hydrogen, and construction of zero-emission ships capable of running on such fuels, remained in their infancy.
Still there have been some promising pilots in recent years. In 2025, the world’s first dual-fuel ammonia-powered vessel demonstrated a successful journey, while hydrogen engine ships also already exist with other demonstration projects underway.
To keep the world in line with a 1.5 degrees C (2.7 degrees F) scenario, the share of ZEFs in shipping should reach 5% to 10% by 2030. Reaching these targets will require policy interventions that increase research, development and demonstration, stimulate demand and drive the transformation of small-scale demonstration projects into a commercial ZEF industry.