In general, this means moving from fossil to non-fossil fuels, produced with renewable or zero carbon energy sources. These fall into roughly three broad categories:
- ‘Blue’ fuels from reformed natural gas with CCS.
- Biofuels from sustainable bioenergy sources (Bio-gas, bio-diesel)
- Electrofuels from renewable electricity, with non-fossil carbon, or nitrogen (SNG, e-ammonia, e-methanol)
Some of these types of fuels, biogas for example, are already in use, for others primarily non-zero carbon options are in testing or soon to be operational in demonstration projects (ammonia and hydrogen). These demonstrations will pave the way for commercial use.
It is hard to identify clear winners among the many different fuel options, but ammonia and bio-based methanol look to be the most promising carbon-neutral fuels currently.
Current IMO regulations only address onboard tank-to-propeller CO2 emissions from fossil fuels. However, the IMO is working on guidelines to determine lifecycle CO2 and GHG emission factors for all types of fuels, including biofuels and electrofuels.
Figure: Timeline for expected availability of alternative fuel technologies - our best estimate for when these may be available for onboard use.
The timeline is our best estimate for when the onboard engine and fuel systems can be expected to be available for use on board (actual availability of fuel is not included as a limitation in the shown timeline).
First demonstration projects (red colour): The technology is ready for demonstration on the ship, and the primary intention will be further development and maturation. Typically, a risk-based approach will address regulatory and safety challenges for the installations. This could require an extensive and costly process of design, approval, and bringing the technology on board.