Several thermodynamically possible ways are outlined in which solar energy could be used to decompose carbon dioxide into carbon or carbon monoxide and oxygen, thereby providing a new source of carbon-based fuels which do not contribute to the environmental problems of mining operations, sulfur pollution, and carbon dioxide buildup in the atmosphere. It is shown that these methods are analogous to cyclic thermochemical processes for the decomposition of water into hydrogen. While these cycles have not yet been proven practical in the laboratory, it is suggested that the thermodynamics are sufficiently favorable that experimental study is recommended. Finally, since the approach has much in common with the hydrogen economy, some of the basic aspects of the hydrogen proposal are reviewed.
