IMO has committed to a 40% reduction in CO2 emissions by 2030, pursuing 70% reductions by 2050 (compared to 2008 levels of emissions.) The European Parliament and European Commission are addressing shipping in their emission reduction targets, as well.

Design, technical, and operational measures including alternative propulsion systems running on non-carbon-based fuels are urgently needed. 

When used in combination with clean drop-in fuel alternatives, internal combustion engines (ICEs) could remain invaluable, DNV GL has stated in recent research. Biodiesel, biomethane, and synthetic natural gas in ICEs must be economically viable solutions to drive sustainable change, and can only compete if they can be reliably procured.

https://splash247.com/why-the-internal-combustion-engine-is-here-to-stay/