Now you can dump energy waste just by, well, taking a massive dump. Green tech company OriginOil is working on a project that uses toilet wastewater as a way to heat apartment buildings.

OriginOil, a start-up based in Los Angeles, CA., has begun a pilot of its urban algae farm concept at the La Défense complex near Paris. Wastewater from buildings nourishes algae growth; algae is processed to make heat. The company is attempting to prove that integrating algae production into large building complexes will help bring them closer to net zero.

OriginOil says its algae farms and photobioreactors can exist on apartment rooftops or even vertically along the sides of high-rise buildings. In this way, designers say, algae systems could compete with solar panels.

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But OriginOil’s algae system boasts a feature that solar panels don’t: Algae can actually absorb carbon dioxide. Plus, the algae can filter out pharmaceuticals from toilet water, which traditional sewage treatment plants can’t accomplish. So you could dump your toilet water into algae panels, and come out with clean water and green heating. That beats the, uh, crap out of what we normally get from flushing the loo.