Red Herring on Climate Change

In the May 7 issue of C&E News, Mitch Jacoby reports on a new polymer to capture CO2. CO2 has various uses, among which are carbonation of soft drinks, fracturing to increase oil production, and a raw material in chemical manufacturer.

The basis of the article relates to reducing carbon dioxide concentration in the atmosphere, which has been said to negatively affect climate change. The article does not say that laboratory studies have shown carbon dioxide is only slightly more efficient than nitrogen and oxygen as a greenhouse gas, but because of its low concentration in the atmosphere, it has basically no additional greenhouse effect.

The composition of the polymer is insignificant. It will have the usual medium cost per pound of chemical. Stability of the polymer for continued reuse has not been determined.

It is said that the polymer selectively removes carbon dioxide and nitrogen from a mixed gas, with about 30 times more selectivity for carbon dioxide than for nitrogen. The component concentrations of the mixed gas were not mentioned. Since the carbon dioxide concentration in the atmosphere is only about 200 ppm, will the selectivity still be 30 to 1?

There is some discussion on using the polymer in membrane form, but a membrane application is only of value if there is restricted pass-through of one gas versus another, with the secondary factor that there is actually no gas absorption by the membrane. This is not the case with the new polymer. In fact, it is stated that the high temperature necessary to de-adsorb CO2 from the polymer reduces the effectiveness of the coal-fired operating plant by about 30%.

The present technology of CO2 capture from a mixed gas, such as electricity power plant emission, is use of an aqueous amine solution, with heating to release the adsorbed CO2. Use of the new polymer will only be practical, if the combination of polymer and hardware costs, with recycle ability and release mechanisms giving a total cost per pound of CO2 less than presently available in the standard amine process.