Exclusive: Science reporter Eli Kintisch, excerpts his book, “Hack the Planet,” on carbon-eating cement

Science magazine reporter Eli Kintisch, sent me a blog post based on the research he did on Calera company for his new book, “Hack the Planet.

So startup Calera, who seeks to turn CO2 exhaust into limestone for “carbon negative” cement, has struck a $15 million deal with coal giant Peabody. And Monday you reported on various issues facing the technology.

I thought I’d offer more: Harvard geochemist Dan Schrag says its CEO is “pulling numbers out of his a##.” And other independent experts have their doubts as to various aspects.

I cover Calera closely in Hack the Planet, my new book on geoengineering. For a chapter on carbon called “The One-Ton-Sucking Challenge,” I spent a day at Calera’s offices in Los Gatos, California and met its business-saavy and brash CEO, Stanford geologist Brent Constanz.


Not only did Constanz disparage mainstream climate scientists (“A philosophy major in college,” he scoffed at one point, obliquely but clearly referring to rival Ken Caldeira). But he relentlessly attacked the idea of storing carbon underground, what he dismissed as “Russian roulette.” Better, he said, to turn the world’s carbon emissions into bricks and cement and buildings. “This isn’t just a niche solution,” he said. “We will be the primary solution.” Calera says it can sequester a ton of CO2 for a mind-bogglingly low $17 per ton.

That (incredible) price is not for making limestone, the firm says. Rather, using less energy, the company could make a solution of bicarbonate ion and inject that into the ground to sequester the carbon.

But regardless of what it makes with CO2, the main chemical challenge for Calera is its need for caustic chemicals known as alkaline solutions, I write in Hack the Planet:

Wrenching the ultrastable carbon dioxide molecule into carbonate takes ultra-strong sour solutions. One of the main reasons why Constantz set up shop at Moss Landing [California] is that a few hundred feet from Calera’s pilot facilities are giant white meadows of alkaline powder, industrial waste known to the locals as Moss Mag.

The problem is, as you wrote on ClimateProgress Monday [see “Does carbon-eating cement (still) deserve the hype?”] — not exactly everyone has that kind of (nasty) raw material handy. Caldeira’s right that fly ash represents a tiny portion of the required alkalinity.


Another problem with fly ash, hydrologist Rob Jackson from Duke tells me: it’s often full of nasty chemicals, so if the bicarbonate slurry were to reach groundwater it could contaminate them. For example, mercury can be found at a level of 1 part per million in it, he says. That’s well above the EPA standard.

Anyway, coal companies (like Peabody, presumably) may well have plenty of alkaline material to use. But elsewhere Calera wants to run electrochemistry facilities next to power plants to make alkalinity, sapping the plants’ energy. Constanz says that electricity can be obtained at night on the cheap. But as you pointed out in your Calera item yesterday, doing electrochemistry means creating huge amounts of hydrochloric acid waste.

A problem that hasn’t gotten much attention yet is that storing the bicarbonate solution — a giant (and therefore expensive) hassle perhaps even a bigger one than storing CO2, I write in my book:

“¦Harvard geochemist Dan Schrag estimates that injecting a ton of pure CO2 carbon dioxide into the ground delivers more than 25 times more of the gas than injecting a ton of bicarbonate, which is only roughly 4% CO2. (Calera says that pumping bicarbonate solution as a partial solid can make up the difference””but geologists worry that injecting solids into the ground will seal up pores in the subsurface rock layers.)

“That’s a real concern,” USGS hydrologist Dave Parkhurst told me yesterday. “If they’re not careful they’ll plug up their wells.”

And there’s the real possibility, say geologists, that the bicarbonate will react with briny water underground, and out will bubble the carbon dioxide. “If something sounds too good to be true, it probably is,” says Howard Herzog. As for the seventeen-dollar sucking-1-ton cost? “My initial reaction is he’s pulling numbers out of his ass,” says Schrag, who has met with Constanz and actually licensed a patent to him.

The scientists I’ve talked to think Constanz may well make some money with the technique. But they’re skeptical that CO2 into limestone is going to be “the solution” to the carbon challenge, or replace injecting CO2 into the ground as a way to deal with emissions from coal.

— Eli Kintisch

Related Post (which goes through some of the chemistry):