Researchers at Penn State have found a friendly microbe that'll take our excess CO2, add some water, a charge of electricity, and return us methane. The original purpose of the portable electrolysis cell research: producing H2. But if you get lemons, make....
It's long been known there are methanogenic microorganisms in marshes, tundra and dumps. In fact, the release of methane from the melting tundra has been a concern of scientists monitoring greenhouse gas releases into our warming atmosphere.
Previously scientists believed these methanogenic organisms turned hydrogen and CO2 into methane. Or simply metabolized already existing organics like acetate. The organic chem texts do not reveal the CO2 + H20 = CH4 formula. The off-gassing of this process: release of O2.
And the researchers on the project see their work leading to inexpensive, portable methane generators. The methane in turn can be bruned to produce more energy than the small amount of electricity needed to power the electrolysis cell. And the process can use electricity during off-peak times to create methane which is a highly portable, clean-burning fuel already widely used in many industrial applications. If the original electricity comes form wind or solar, the whole process becomes carbon neutral.
Depending on how long ago you studied biology, this whole process depends on a group of micro-organisms you may not be familiar with. It is the third, and most recently described Domain of living organisms, Archaea. The other Domains: Bacteria and Eukaryota (plants, animals [that would be you], fungi and their ilk).
Archaeans live in environments hostile to other life forms, even politicians: hot springs, underground oil deposits, highly alkaline or saline liquids, anoxic mud, termite stomachs. You try that sometime.
Archaea are less than one micron in size, but you can see some magnified images here. Typical Archaea structure. Courtesy U.C. Berkeley