Turning CO2 into Cement

The New York Times
highlights a new technology that turns carbon dioxide emissions from coal and gas power plants into the basic inputs for cement. Calera, the Silicon Valley start-up creating the approach, has received some $50 million in financial support from venture capitalist Vinod Khosla. Peabody Energy, one of the world’s largest coal company, has put $15 million into the idea. While still relatively small numbers compared to overall investments in fossil fuel-related technologies, these first funds signify growing investment in turning CO2 into a reusable, non-polluting resource.

Calera will combine CO2 with “seawater or groundwater brine, which contain calcium, magnesium and oxygen. It is left with calcium carbonate and magnesium carbonate, which are used in making cement and aggregate. It plans to sell it to concrete companies for use in pavement.” To convince building manufacturers that their material is safe, Calera’s CO2-embedded cement is being mixed with Portland cement, the “calcium silicate” binder used in concrete for buildings and transportation infrastructure.  Turning CO2 into building materials will make “carbon reduction attractive,” argues Brent Constantz, Calera’s founder and chief executive.

Coal power plants are major emitters of CO2 emissions. Cement production also contributes large amounts. Creating a cycle wherein the coal plants’ waste becomes feedstock for cement will help kill two birds with one stone. Vinod Khosla said: “With this technology, coal can be cleaner than solar and wind, because they can only be carbon-neutral.”

R.W. Beck examined Calera’s process and determined that its cement process captured 86 percent of CO2 from a flue gas in one power plant. Seawater and flue gas CO2 are the two key inputs into the process; cement, waste seawater, and a harmful acid are the putputs. The waste sea water that comes out of the tail end of the process can be de-salinated, but the acid, if produced in bulk, could create environmental problems, writes The New York Times. “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.”

Some scientists raise doubts the firm can pull it off, arguing that the idea has been explored for more than 15 years. There have been earlier failures, largely due to the costs involved. Beyond the costs of the actual process, infrastructure costs associated with scaling this up (and dealing with potentially massive amounts of that toxic acid) also need to be addressed. Ken Caldeira, a researcher at the Carnegie Institution for Science at Stanford, says: “The idea that they’re going to come up with something that’s both economic and scalable? I’m highly skeptical.”

But other options are also very expensive. Carbon capture and sequestration demonstration projects all show that these projects are multi-billion dollar undertakings. Injecting CO2 into the ground may not be stable in many parts of the world. (see earlier post)

On Calera’s web site, the firm outlines their initial target markets, which mostly involve infrastructure: “We will first introduce our […] materials into applications such as pavements and road base course. We will be introducing SCM into applications such as pavers, non-structural block, other miscellaneous precast products, sidewalks, and other similar applications.”

Read the article

Also, check out another technology that would reuse waste products while reducing CO2 emissions.  MIT Technology Review discusses a new process that would turn cellulose from agricultural waste into gasoline and jet fuel. “The process is one of a number of new technologies that make conventional fuels such as gasoline and diesel from biomass rather than petroleum.”

Image credit: Calera

2 thoughts on “Turning CO2 into Cement

  1. Owen Dell 03/31/2010 / 3:24 pm

    OK, let me see if I understand this. This process will generate massive amounts of toxic acid waste with no plan whatsoever for their safe disposal. It doesn’t capture all the flue gas from coal burning power plants. It encourages the use of coal, which means more strip mining, mountain top removal, stream degradation, and destruction of habitats, communities, and lives. And it’s a non-structural material, which means it’s not as strong as conventional concrete. Finally, the cost will probably be prohibitive. Gee, it’s no wonder Peabody is funding it.

    I’m all for tapping the waste stream, sequestering CO2 and helping the environment. But this proposal sounds like another half-baked scheme to benefit the very system that has caused the problem in the first place. I’m not falling for this one.

  2. Pieter 04/29/2010 / 5:52 pm

    This new product reminds me of E-crete and NavajoFlexcrete which are made from waste products produced from coal fired power plants. Basically toxic heavy metals turned into building products. It might be good for road base but to be used in building products for homes and even pavers is questionable. I have seen these products being used and the waste left over is considered hazardous material. I think more research should be done on these products before they are used to house humans.

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