The carbon vault
Service, Robert F.
Every year, mining and industrial activity generates billions of tons of slurries, gravel, and other wastes that have a high pH. These alkaline wastes, which sit either behind fragile dams or heaped in massive piles, present a threat to people and ecosystems. But alkaline wastes could also help the world avert climate disaster. Reacting these wastes with carbon dioxide (CO2) from the air converts gaseous carbon into minerals and neutralizes the wastes' alkalinity. Carrying this out on a global scale could trap between 310 million to 4 billion tons of CO2 annually, according to recent surveys. That could provide the world with a much needed means of lowering atmospheric CO2. But there are major hurdles. Governments will need to offer incentives for mineralization on the massive scale needed to make a dent in atmospheric carbon. And engineers will need to figure out how to harness the wastes while preventing the release of heavy metals and radioactivity locked in the material.</p>
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