Calera v. Caldeira: The Great Cement Controversy

Every year the world produces 2.5 billion tons of cement, enough for 9 billion cubic yards of concrete that could pave 16 highway lanes from the Earth to the moon.

The production of all that cement, which requires heating limestone and other materials to about 2,600F, contributes as much as five percent of all CO2 emissions, making it a major cause of global warming.

As previously described in NEXT100, traditional cement companies and a growing number of startups are exploring novel production methods to radically reduce or even eliminate their net output of carbon dioxide.

Now one of the most promising–and most controversial–of those companies says it has begun to make cement on a significant scale by drawing carbon dioxide from Dynegy’s huge Moss Landing power plant.

Los Gatos-based Calera claims its process for making cement actually locks up more CO2 than it produces. The manager of the Moss Plant Power Plant calls it “probably one of the best carbon-capture processes out there that we know of today.” And Carl Pope, executive director of the Sierra Club, said “It changes the nature of the fight against global warming.”

Those are extravagent claims, but Calera’s founder, Brent Constantz, has serious credentials. He is a consulting professor at Stanford University and founder of three previous companies. He convinced noted venture capitalist Vinod Khosla to fund his firm. And he can point to a patent issued in Australia to support some of his claims.

But a lot of people don’t believe him, including cement industry rivals and, more disturbingly, fellow scientists. One of the most noted critics is Ken Caldeira, a distinguished geochemist and climate expert at the Carnegie Institution, located on Stanford’s campus.

It doesn’t help that Calera’s web site is notably short on technical details or that the company  has been operating at Moss Landing for over a year and a half without much in the way of public results.

So who’s right, Calera or Caldeira? Here’s hoping that Calera is for real and Caldeira is uncharacteristically wrong. The world needs a game changer. But it can’t wait forever to see results.

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