Hydrogen is definitely the fuel of the future. Or, it would be, if we had a fast and easy way to make all the hydrogen we need instead of sucking it out of hydrocarbons like natural gas. It now looks like the way to go is just harnessing bacteria to do all the hard work for us, for free.
In a conventional fuel cell, separating hydrogen from water takes electricity. And electricity (unless you get it from solar or something) usually means some kind of waste product, which to some extent will cancel out all the eco-fuzzy happiness you get from the hydrogen. So with "free" hydrogen, you'd want to be able to create it with zero inputs and zero outputs, and while that's not physically possible, this new "reverse electrodialysis bacterial hydrolysis" fuel cell manages to create nothing but hydrogen using nothing but waste water and salt water as inputs.
Here's how the magic happens: microbial fuel cells can produce hydrogen from water, but the bacteria themselves aren't quite strong enough to do the whole job without additional electricity. To get the extra energy, this fuel cell uses what's called a reverse-electrodialysis stack, which uses the ionic differences between salt water and fresh water to create just enough electricity to enable the microbial fuel cell to do its job. All you have to do to get this setup to produce hydrogen, then, is to put seawater into one side of it, and river water or waste water or any other source of fresh water with enough organic compounds for bacterial to feed on in the other side, and sit back and watch the hydrogen flow. For every cubic meter of liquid you put in like this, you'll get out between 0.8 and 1.6 cubic meters of hydrogen, but this'll scale up. And remember, it's totally and completely free.
This device is mostly just a proof-of-concept type thing and obviously not ready for production, but when it is, it could mean household fuel cells that treat waste water and produce unlimited, free hydrogen to power your car and your gadgets all at the same.