This German building, called BIK, is covered by panels filled with algae. The building pumps water, nutrients, and compressed CO2 to these panels, so that when the sun shines, the algae multiply. The system collects the algae residue and converts it to biogas, which is then burned to create usable energy. Together with a heat recovery system and solar panels on the roof, the building is completely energy independent.
Via Fast Company.