My review of Broecker and Kunzig’s book Fixing Climate drew attention to the work of Klaus Lackner, a physicist at Columbia University who has been working on ways of scrubbing CO2 out of the atmosphere for sequestration. Lackner considers sequestration the harder problem of the two and believes that the only method adequate in the long-term is mineral sequestration, achieved by hurrying along the natural process geochemical weathering whereby rocks react with CO2, removing it from the air to form limestone and other carbonates.
Colombia’s Earth Institute has recently released news of mapping by geologists of ultramafic rocks at or near the surface in the US. Originating deep in the earth, these rocks contain minerals that react naturally with carbon dioxide to form solid minerals. The report of the scientists indicates that there could be enough rocks, most of them in and around coastal ranges, to stash more than 500 years of US CO2 production.
Another University of Columbia geologist Peter Keleman has been working in Oman studying the peridotite, a highly-reactive ultramafic rock, that covers about half the landscape of Oman, and appears at scattered locations worldwide. He and biochemist colleague Jeurg Matter report that Oman alone could potentially sequester 4 billion tons of CO2 per year, one-eighth of the 30 billion tons of CO2 humans emit annually.
The key is the speeding of the natural process. Matter and Keleman suggest that the natural process could be accelerated 100,000 fold in the Oman rock. Scientists are experimenting with a method of dissolving carbon dioxide in water and injecting it into the rock. Heat would be added initially to accelerate chemical reactions, but as new carbonate rock begins forming, the process could start feeding on itself, with new carbonate rock continually fracturing the host rock further, and the heat from the reaction supplementing the deep-Earth’s heat.
Matter is also involved in an experiment in Iceland to inject CO2-saturated water into basaltic formations there. A paper on the project written by Matter and Broecker and others can be seen here (pdf).
Fixing Climate spoke of rock sequestration as providing space for the dream that we might clean up the mess we are making by burning fossil fuels. The scientists associated with the issue are obviously not content with dreaming.