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."

However, some scientists remain highly skeptical, arguing that this idea isn't new and has been explored for more than 15 years. 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."

The infrastructure costs associated with scaling this up (and dealing with that toxic acid) also need to be addressed.

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."

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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