Cargo ships could switch to renewable fuels, but it ain?t cheap (yet)

That means that the amount of electricity required to produce each fuel has an impact on cost, as well as the requirements for storage and transport (which is trickier for hydrogen and methane).Allowing for a 3 percent cargo reduction and assuming ships would only carry as much fuel as they need, the number of 2018 shipping voyages that could be handled (without stopping to recharge/refuel) varied. Current lithium-ion batteries could only cover a small number of voyages—though possible battery advances could push that number closer to half.The chemical fuels are considerably more energy dense than batteries, so liquefied hydrogen was suitable for about 93 percent of those voyages, and ammonia, methane, methanol, and diesel each cleared 99 percent. Absent generous public subsidies, this wouldn’t be a financial investment.The high cost isn’t set in stone, though—if prices go down as the technologies mature, this isn’t necessarily the showstopper it might seem.Among the fuel options, ammonia stands out as the cheapest, while renewable diesel is the most expensive. Although it's not the only factor in the cost, there are significant differences in the amount of electricity required to produce each—some fuels allow relatively efficient conversions of electrical energy into chemical energy.Hydrogen made by splitting water looks good on that measure, but this bit of economy is outweighed by the cost of storing and transporting this fuel.