Ships already emit 3 percent of all greenhouse gases, and if the sector proceeds on a business-as-usual course, emissions are expected to increase by up to 50 percent by 2050. It takes a lot of energy to haul a ship across the sea, and as world trade increases, there is a growing number of ships to haul. Any of this energy may be lowered to minimize pollution by ships using more compact designs, adding wind harnessing systems, traveling a little slower to save power or even bringing less material. Ultimately, though, if shipping is going to decarbonize entirely, and if the world is to remain within reasonable temperature limits, it would have to find a fossil fuel substitute, for which Green Hydrogen is the major candidate. Once the hydrogen is produced, there are several ways it can be used to power ships.
It can be burnt in an internal combustion engine or can be used in fuel cells and another way currently being researched is driving a turbine generating electricity using steam generated by burning hydrogen with pure oxygen. But the real difficulty of using it in long-distance shipping is how tricky it is to store it. Hydrogen cannot simply substitute bunker fuel in the existing method. In order to store it on board a ship as a liquid, it needs to be frozen at cryogenic temperatures of-253C, and it also takes up a lot of space-about eight times more than the amount of marine gas oil used to supply the same amount of energy.