Typically, Cyanobacteria utilize sunlight, water, and CO2, and then "exhale" oxygen, under aerobic conditions. The source of the CO2 is of interest here. According to Joule Unlimited, the source is "waste CO2", whatever that means. References to their super secret plans are linked to from Wikipedia (#19) from when it was first patented (sorry, can't seem to paste link here).
One good reason why computers can do more work than people is that they never have to stop and answer the phone.