A team at the Bristol Robotics Laboratory put a new spin on the idea of waste-to-energy: The waste they start out with is pee. Which they use to generate electricity. (Beat that, Kevin Costner.)

The system works by passing urine through a microbial fuel cell. As Ioannis Ieropoulos explains, the fuel cells contain little organisms and “those little organisms eat the fuel that we give them, and by eating it — breaking it down — they produce electrodes … urine is exceptionally good as a fuel for those microorganisms.”

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So far Ieropoulos and his colleagues have managed to charge a Samsung phone enough to send a few text messages and make one call. That’s not a ton of power, but the next goal for this technology is to improve the output — of the cell, not of the human bladder. That, Ieropoulos says, is already dependable enough:

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One product that we can be sure of an unending supply is our own urine … The beauty of this fuel source is that we are not relying on the erratic nature of the wind or the sun; we are actually re-using waste to create energy.

Just keep hydrated. We can already imagine how frustrating it’s going to be when you’re stuck in a desert and your pee-powered phone runs out of batteries.