People here because of the NYT link might want to start with “An Introduction to Climate Progress.”   My bio is here.

I’m quoted in today’s NY Times article on Calera.  The “Silicon Valley start-up says it has found a way to capture the carbon dioxide emissions from coal and gas power plants and lock them into cement.”  I wrote about the company — and its critics — last April (see “Exclusive: Does carbon-eating cement deserve the hype?“).

The hype is still there, as this absurd quote from Silicon Valley billionaire Vinod Khosla makes clear:

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“With this technology, coal can be cleaner than solar and wind, because they can only be carbon-neutral.”

Khosla keeps pushing these nonsensical statements that undermine his credibility (see “I would venture that the cleanest power will not be solar, it will be coal” and A pragmatic view of cellulosic biofuels or why VC Khosla is very wrong and VC Khosla blows his credibility dissing plug-ins.

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At best, the Calera process couldn’t do more than capture and sequester the CO2 from a coal plant, so that wouldn’t be cleaner than solar and wind.  And you’d still have to capture 100% of the CO2 from the plant, which is unlikely, and sequester it for a long, long time since  “the burning of organic carbon warms the Earth about 100,000 times more from climate effects than it does through the release of chemical energy in combustion” (see “Why solar energy trumps coal power“).

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And that assumes this process actually does what Calera says and is scalable, two propositions that remain in doubt, as the NYT notes:

Some climate scientists and cement experts are dubious that Calera can produce large quantities of cement that is durable and benign for the environment.

“People have been looking for ways to do this for 15 years,” said Ken Caldeira, an expert on the carbon cycle who is a senior scientist with the Carnegie Institution for Science at Stanford. “The idea that they’re going to come up with something that’s both economic and scalable? I’m highly skeptical.”

I am not going to repeat here my extended discussion of Calera from April 2009, which included climatologist Ken Caldeira’s chemistry analysis of the company’s process.  Caldeira made a strong case that

  • The scalability of the process is in doubt
  • We won’t know if net CO2 is saved unless Calera is much more forthcoming on all of the inputs and outputs

Caldeira emailed me several days ago that nothing he has seen has changed his basic view.

I ended that 2009 piece repeating Dr. Caldeira’s statement that Calera needs to provide the “inputs to and outputs from their process, in a way that allows balances of mass, energy, and electric charge to be assessed” independently.

The NYT notes today, “the company declines to share precise details of its process.”  Until those details are shared, no statements about “coal can be cleaner than solar and wind” should be given any credence, and all company claims about emissions benefits and scalability should be viewed skeptically.

The scalability issue is ultimately the most important because we need massive amounts of zero-carbon technology to avert catastrophic climate impacts (see How the world can stabilize at 350 to 450 ppm: The full global warming solution).  Even if the company could achieve some emissions benefits in niche applications, the hype could only be justified if it could achieve large emissions benefits in broad application.  That, too, remains in doubt, as the NYT notes:

Much of the skepticism about the project stems from the acid created in Calera’s chemical process. It has to find a way to dispose of it or neutralize it by adding alkaline materials, without creating more environmental problems or raising costs. Either would be difficult to do on a large scale, Mr. Caldeira said.

Mr. Khosla said that Calera has many sources of alkaline materials and many ways to dispose of acid.

If so, then Khosla and Calera should be happy to explain what these sources are and disposal methods are — and what the entire process is.

Climate scientists have raised other questions as well. “The chemical processes are known to exist, but if what you’re looking for is something that can be scaled up in order to actually mitigate CO2 emissions, it’s just a big problem,” said Ruben Juanes, assistant professor in energy studies at M.I.T.

Growing beyond the demonstration plant will be Calera’s next challenge, and it is a step that has stumped many clean technology start-ups.

“People have the impression that the energy sector is like the I.T. sector and you just have to build an iPhone and suddenly it will be everywhere, which is simply not the case,” said Joseph Romm, senior fellow at the Center for American Progress and editor of Climate Progress, an influential blog. “You have to build up so much infrastructure.”

People build cement factories for a long time, so building up an entirely new infrastructure simply can’t happen fast.

Since we need all the carbon-reducing strategies we can get, let’s hope Khosla and Calera have something that is effective and scalable.  But there is no reason to believe they have — until and unless they answer the questions posed by their critics in detail.

UPDATE:  Caldeira sends m
e this note today:

Instead of telling us what they plan to do, Calera is providing us with cartoons.

When people describe a chemical process and inputs and outputs, it is conventional to give formulas for chemical reactions and then describe from where you intend to source the reactants and what you intend to do with the reaction products.

Cartoons don’t really do the job.

There is one cartoon, labeled “our process”: index.php/technology/ our_process/

By my quick and possibly erroneous calculation, fly ash should be able to handle something on the order of 0.1% of US CO2 emissions. This might be good but does not seem scalable. I do not understand what Calera is planning to do with brines. I do not understand what “Electrochem” means.

There is another cartoon, labeled “inputs and outputs”: technology/ inputs_outputs/

Again, what is need is some chemical specificity. What is “manufactured alkalinity” — accelerated silicate rock weathering? What chemistry are they planning to apply to brines? What kind of waste water? etc.

In short, this is not enough specificity to judge definitively what they proposing to do.  Given the lack of information, I would have to put it as “I see no evidence that they have found an affordable and scalable process, but it is impossible to say anything definitive because they are not being adequately forthcoming.”