The Energy Costs Of Caching Carbon
The treatise on carbon dioxide sequestration in the September cover article of Environment Hawai`i is a heroic effort, based on what the scientists and the environmentalists have propounded. However, I have found missing from all the discussions on this project any question on the proper approach to the science and engineering of such a scheme. One of the very basic questions that should be asked is the net energy expenditure versus the removal of CO2. It takes energy to collect/separate, transport and compress the gas to force it down to the depths. The CO2 generated to produce the energy for this process may significantly offset the amount sequestered. This question is somewhat analogous to the “break-even” question in nuclear fusion research – the point at which the fusion energy generated is equal to that required to create the condition for sustained fusion to take place.
Actually, both the question of net gain in CO2 reduction and the chemistry and physics of this deep ocean sequestration concept can be answered to a great extent by laboratory experiments at small scale. Then, through appropriate modeling, these answers can be used to project how sequestration might work in the real world. And all this can be done before committing to huge sums of money and triggering all kinds of environmental questions along with all the political problems.
I suppose things tend to escalate very fast because of our contemporary addiction to Big Science, particularly when one can attach the Global Warming label to it. An example of a project that fits this model quite well comes readily to mind: ATOC, or Acoustic Thermometry of Ocean Climate, which invoked the magic words G W. Of course, after six years and $50 million the project has not made any connection whatever towards the goal of helping to verify the climate models proliferating worldwide. (Very cleverly, the Scripps Institution scientists have now turned things around by claiming the purpose of ATOC – known now as North Pacific Acoustic Laboratory — is the study of ocean environmental factors on the propagation of underwater sound. The flip-flop is even in the new name!)
I would humbly suggest to the sequestration cadets that they should do some low-key, not very expensive laboratory-scale studies, which can even include the environmental/biological effects, before they venture into Big Science and Big Politics.
On a related tack, I just came across an excellent book, The Two Mile Time Machine, by Richard Alley, a paleoclimatologist at Penn State. He discusses the study of ice cores from Greenland and Antarctica and how this opens a pretty good window on the Earth’s climate over the past three to four hundred thousand years. One particularly interesting aspect of this type of work, vis-a-vis the carbon sequestration and NPAL projects, is that it involves a very small community of scientists (with no more than two dozen what one might consider prominent names) working quietly, but generating a tremendous amount of significant data. Ironically, the real data they have acquired can be used (and is being used to an increasing extent) by both sides of the global warming arena.
I highly recommend this book to those who wish to learn something about the earth’s climatic history outside the hype and passion of the politico-scientific GW arena.
Ray Chuan, Ph.D.
Hanalei
Volume 12, Number 4 October 2001
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