Cargo ships will eventually run on green hydrogen as will commercial airplanes because batteries carry too much weight and need to be charged much more frequently than filling these modes of transportation with green hydrogen..
They may very well
eventually do this (Im an advocate.) However, the technology to accomplish that is not available
today (R&D continues) and, even if it were, we do not have time to either retrofit the various fleets, or replace them all.
Today, it is easier to
replace their fuel with something which is either generated using electricity or (indirectly) from green hydrogen (like green ammonia for example.)
https://newatlas.com/energy/green-ammonia-primer-clean-fuel/
Indeed, in many ways, ammonia does a better job of storing hydrogen than hydrogen gas itself; H2 is notorious for leaking away through the metal walls of containers, for embrittling steel it comes into contact with, and for taking a lot of energy to liquefy at cryogenic temperatures. And then there's density: it may sound weird, but there's one and a half times more hydrogen in a gallon of ammonia than there is in a gallon of hydrogen, all else being equal.
Today, bio-diesel is (essentially) being made from
food.
This is not sustainable, but it is seeing increasing use, converting large areas of forest into farms to produce it.
Like green hydrogen this is a way to generate fuel using electricity. Unlike green hydrogen it also uses CO₂, and creates an alternative fuel that
could be used by todays fleet. (It too requires R&D.)
https://source.washu.edu/2024/11/researchers-create-novel-electro-biodiesel-more-efficient-cleaner-than-alternatives/
This research proves the concept for a broad platform for highly efficient conversion of renewable energy into chemicals, fuels and materials to address the fundamental limits of human civilization, Yuan said. This process could relieve the biodiesel feedstock shortage and transform broad, renewable fuel, chemical and material manufacturing by achieving independence from fossil fuel in the sectors that are fossil-fuel dependent, such as long-range heavy-duty vehicles and aircraft.