It's a chemical combustion reaction, a exothermic reaction, producing energy of 572 kJ. (realclimate.org)
His reasoning was based on the fact that water vapour as a greenhouse gas is much more prevalent, potent, and thus much more powerful than carbon dioxide — and because combustion reactions also produce water, it should be water vapour we're worried about, not carbon dioxide. (rationalwiki.org)
But I do have at least a smattering of ordinary non bio chemistry; and to me it would seem that CO2 is simply the effluent from one of the two most apparent stored chemical energy combustion reactions; the other one being H2O which is the effluent from combusting Hydrogen. (wattsupwiththat.com)