the feedstock for the fuel (fossil coal/petroleum/natural gas vs. sustainable “green” H2 or biofuels)

the technology for distributing and using it (liquid fuels and combustion engines vs. gaseous fuels and fuel cells that provide electricity)

With “the hydrogen economy,” a huge emphasis is placed on the latter of those two issues, while the former is just sort of hand-waved as a trivial detail we’ll get to later, even though transitioning from “gray” to “green” hydrogen is also a huge unsolved problem that isn’t trivial at all.

e-fuels or bio fuels are only short term solutions that are greenwashing because in the short term there is insufficient green H2 abundance. Their only value is to keep using your existing machinery.

For new machinery/transportation, a fuel cell is 2x the efficiency of a combustion engine. It is a range extender for any battery electric machine/home, with usable waste heat. A green economy involves people eventually going back to buy fossil fuels from drug stores, because there eventually are so few machines that use them. It is greenwashing to say "we want to keep everything the same except just have very expensive gasoline".

It's simply ok to make new H2/Ammonia consuming machines that displace older machines even as people are not forced to upgrade until they are ready. In long term, H2 will always be cheaper than e-fuels in addition to being 2x the energy value with far more flexible use.