Many methods of carbon sequestration are quite high tech. In some cases the carbon is removed as CO2 during the industrial processes that produce it, then converted to an easily transportable solid or liquid, then buried beyond reach in deep caves or under oceans in now-dry oil or gas wells. There’s a promising new idea, Kevin Bullis tells us in Wired, from scientists at the Santa Cruz campus of the University of California. It uses the interaction of seawater on limestone, in much the same way that caves are carved out by the sea in limestone.
The process proposed replicates that and accelerates it. CO2 in water makes the water slightly more acidic, and acts upon limestone to form calcium bicarbonate, the soluble salt that’s a constituent of hard water. When exhaust gases are exposed to crushed limestone, it is possible to remove 70 – 80% of a power plant’s carbon dioxide and put it into seawater as soluble calcium bicarbonate. The salt already is in seawater as a result of natural processes, and there would only be a marginal increase in its concentration even if the world’s coastal power plants all switched over to this technology. Many power plants already pump seawater for cooling, so the problem would be getting the limestone to them in sufficient quantities. This calls for a pilot power plant to test that the system does indeed out as efficiently, cheaply and safely as it promises to. Oh, and there’s a modest and unexpected bonus: the calcium bicarbonate could make the seas locally rather less acidic than they are being made by increases in atmospheric CO2.
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