Scientists have used algae to power a low-energy computer chip for six months. Researchers from the University of Cambridge sealed a colony of cyanobacteria, commonly known as blue-green algae, inside a metal enclosure the size of an AA battery.  The algae-powered ARM chip was used to carry out very basic calculations, during which it consumed a tiny 0.3 microwatts an hour.

Although the energy usage of normal computers varies based on factors like workload and age, this is a sliver of the electricity needed to run an average PC. If a normal desktop computer consumes, say, 100 watts of power an hour, you would need roughly 333,000,000 algae “batteries” to run it.

Source: Energy & Environmental Science