Answer: algae

In Hamburg, Germany, exists what is thought to be the world's first building powered partly by algae.

Designed and built by Splitterwerk Architects and engineering firm Arup, the building, called the BIQ house, has a "bioreactor" facade that is reportedly the first using algae within its glass-paneled facades to both generate energy and provide shade to the working building, Gizmag reported.

The BIQ was showcased for the first time on March 23 at the opening of the International Building Exhibition in Hamburg, and the integrated algae-based system will be put into full operational mode at an inauguration event for the media on April 25, according to Arup.

Photos courtesy of Arup