Can we extract commercial products from waste CO2?

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Skyonic have developed “Skymine”, a system that not only extracts CO2 but actually turns it into something they can sell!
Read a transcript of the interview by clicking here
or [chapter podcast=3300 track=11.06.19/Naked_Scientists_Show_11.06.19_8669.mp3] Listen to it now[/chapter] or [download as MP3]
« Last Edit: 21/06/2011 23:01:02 by _system »


Offline damocles

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Can we extract commercial products from waste CO2?
« Reply #1 on: 22/06/2011 10:29:30 »
That is a very up-beat interview, and it looks as though Skyonic have found themselves a very useful little niche market, But is there really any chance to develop that technology on a larger scale?

A physical chemist with an interest in energy and environmental impact issues will tell you that it is always important to do a "dawn to dust" analysis of a proposed product or process.

Two processes are mentioned here -- conversion of carbon dioxide to calcium carbonate, or to sodium carbonate/bicarbonate.

For the calcium process firstly. Calcium carbonate is a very useful material. It is usually obtained by quarrying limestone, and it may possibly be cheaper in both energy and money terms to use a process like the one outlined here than to continue quarrying ... BUT ... as I understand it calcium carbonate is used mostly in the preparation of two other materials -- portland cement for concrete, and quicklime for a variety of purposes in construction, gardening/agriculture , and manufacturing industries. And the preparation of either of these products. unfortunately, involves the release of the same amount of carbon dioxide as the process has just sequestered! Oh, and quicklime is also needed for the initial sequestration of carbon dioxide in this process anyway.

Conversion of carbon dioxide to sodium carbonate and/or bicarbonate is much more complicated. The process suggested in the interview is firstly to obtain caustic soda by the electrolysis of concentrated brines (chloralkali process), and then to use the caustic soda to sequester the carbon dioxide. The electricity is probably produced via fossil fuel combustion, but a 50%-ish net gain is suggested in the interview. The amount of CO2 produced in generating the necessary electricity is only about  half of the amount sequestered in the process.

Sodium carbonate and bicarbonate are useful materials, but I suspect lower volume materials than calcium carbonate. I know about their household uses in washing soda and baking soda, but can anyone fill me in on their industrial uses? And, in their normal mode of use, is the carbon dioxide likely to remain sequestered, or to be released back to the atmosphere?

There also seems to be a problem inherent in the chloralkali process. In one way it is a valuable process because it generates two very useful materials -- caustic soda, and chlorine gas. But I remember a discussion a few years ago when someone told me that Australia's last chloralkali plant had just closed down, and that we imported nearly all of our caustic soda from Asia. When a process generates two valuable products, there is an economic difficulty with how to price each of them -- how to apportion the proceeds of the operation between the two saleable products. A great imbalance had occurred at least in Australia. The nation was addicted to aluminium production, which consumes large amounts of caustic soda (as well as energy) and it was no longer making PVC (a consumer of chlorine gas) on shore. Not only that, but use of chlorine in bleaches and disinfectants, and use of organochlorine compounds as solvents and cleaning agents had also become much more restricted because of a greater recognition of their safety and environmental issues. So, of the two products, the caustic soda was in huge demand, while there was a greatly reduced demand for the chlorine gas which was always produced in equivalent amounts as a co-product, and was nasty and dangerous stuff in its own right!

The processes suggested and developed by Skyonic -- very successfully, if the interview is to be believed -- might certainly fit a niche opportunity in a local market, But I greatly doubt that they can contribute much, if at all, to any global strategy for CO2 sequestration.
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