The best method of carbon sequestration

Now that the Bush administration has admitted something every thinking person already knows–that the world is warming–and now that the administration is fully behind the search for alternative fuels, we can expect more talk about the benefits of carbon sequestration.

For some people carbon sequestration offers the best of all possible futures. Presumably, we could continue to burn plentiful coal supplies long after oil and natural gas production declines. With the proper technology we could then capture the resulting carbon dioxide (the main greenhouse gas) before is it released into the atmosphere. This would supposedly give us the necessary breathing room to make a gradual transition to a renewable energy economy with a minimum of disruption.

The initial schemes for sequestering carbon such as placing it in caverns underground sound easy enough. But several concerns arise. Can leaks be avoided, not just immediately, but over a period that might last many thousands of years? Will the carbon dioxide react with the surfaces of the cavern opening up pathways to the air above? Such reactions have been noted, but whether they would ultimately result in substantial leaks remains unknown. Can all the existing drill holes into such a cavern be found, adequately sealed and monitored for an indefinite period of time? In other words, who will be babysitting these sites 100, 200, even 500 years from now?

One sequestration scheme already in use stores carbon dioxide in an aging oil field. The injected CO2 is used to force out the remaining hard-to-get oil. As clever as this seems, it’s worth asking whether any net reduction in greenhouse gasses occurs since the recovered oil is ultimately burned?

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