My naive question would probably be "Don't plants already do this for us?", but I'm probably not understanding the problem that they hope to solve with this technology.
Nope. The CO2 produced from burning coal/gas is normally just vented into the atmosphere. This is why we have global warming.
Other toxic stuff like nitric and sulfuric oxides are captured to meet emissions standards.
He uses the word "plants" to mean the green leafy type.
Yeah, this doesn't mean "free energy", but it's a way to potentially recapture CO2 emitted from a power plant or other major source and put it back into the energy cycle.