G.Gonzalez and Jay W. Richards: THE PRIVILEGED PLANET, page 56:
Life relies on chemical energy for its immediate metabolic needs, and chemical energy is all about the exchange of electrons. Hydrogen, and carbon combined with hydrogen, or hydrocarbons, are the best substances to combine with oxygen. All complex life forms use such oxidation reactions (other common reactions yield far less chemical energy). And not incidentally, the products of oxidation are water and carbon dioxide, the nontoxic and essential components of the climate regulation system.
Isn't God ingeniously smart?