There are intermediate options. Moving away from diesel towards natural gas would dramatically reduce emissions (including sulfur emissions), while retaining high energy density.
Unlike diesel fuel, gas fuels are readily ignitable and present a suffocation hazard in enclosed spaces. This is solvable with installation of a proper gas detection system, but if you've ever dealt with the shipping industry you'll know that maintenance is not top of their list.
Also gas fuels require new port-side storage and handling equipment, and in the case of liquified gas this might require a refrigeration system.
Electricity on the other hand is already port-side, and most ports will have a significant supply available.
As for weight, that's not really a problem for ships, especially tugboats. In the case of tugs the near instant peek power of electric propulsion is a huge advantage.
So, we're keeping the fire hazard, but adding a stored energy hazard in the form of compressed gas? All in a retrofit? This doesn't sound like a good idea for international ships.
> and most ports will have a significant supply available.
Are you sure about that?
Indeed not, I haven't heard of any large cargo ship using gas fuel at sea other than gas carriers. I know that there are some dual-fuel ships, which use gas fuel in costal waters for emissions reasons, but they carry much less gas than would be required for a full voyage.
> > and most ports will have a significant supply available.
> Are you sure about that?
Ports have electric cranes (the big ones, not the straddle cranes), shore power supply for ships, bulk goods handling facilities, etc. They often have a high voltage (110kV+) supply. This won't be true everywhere, but it is common.
Of course it's not just a drop in process and it will be expensive to get all the new equipment in place.
My nearest port got their first electric tug two years ago and they documented what they needed to do. They did have to install a new substation, but their existing 110kV feeder lines have plenty of capacity, they already consume over 13GWh per year so the increase needed to charge the tug wasn't high.
I am ignoring the issues with charging battery-electric large cargo ships because the article did not consider those either.