Very Alternative Energy: Bacteria, Sewage and Saltwater

Most of the renewable energy sources that are under consideration involve an obvious source of energy—light, heat, or motion. But this is the second time this year there has been a paper that has focused on a less obvious source: the potential difference between fresh river water and the salty oceans it flows into. But this paper doesn’t simply use the difference to produce some electricity; instead, it adds bacteria to the process and takes out a portable fuel: hydrogen.

Nobel Intent brings us: the poop power plant. When freshwater meets saltwater with a membrane between (through which water cannot pass), ions will pass from the saltwater to the freshwater, creating a potential difference = power. Meanwhile, bacteria can liberate electrons in the process of digesting organic matter. Neither of these alone create much voltage, but when you combine them (not so clear on how this part works), you have enough voltage to release hydrogen from water molecules, which you can later use for power in fuel cells. You also need organic matter for bacteria to digest, so a potential system to use this in is, for example, where sewage empties out.

And there you have it – poop power plants. The future may not be as shiny and clean as we thought…


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