C_005 - There's a battery technology called "magnesium-air." These batteries are about five times more powerful than lithium batteries. Since they run on magnesium, salt water, and activated carbon, I was wondering if it might be interesting to use them for container ships that use petroleum-based fuels, which are currently highly polluting. After all, magnesium is extracted from seawater; salt water is already present in the sea. As for activated carbon, I believe that's also a material that's extremely inexpensive to produce, as, if I'm not mistaken, it's obtained from the burning of spent coal, which is quite common.