Forget Carbon Capture – make Green Cement from Power Stations

Carbon capture and storage (CCS) is one of those technologies, like first gen biofuels, that seem like a good idea at first sight but when you examine them you find do more harm than good

CSS is a means of mitigating the contribution of fossil fuel emissions to global warming. The process is based on capturing carbon dioxide (CO2) from large point sources, such as fossil fuel power plants, and storing it in such a way that it does not enter the atmosphere, such as underground.  In theory 80-90% of emissions could be captured, and initially the IPCC was enthusiastic, estimating that between 10% and 55% of the total carbon mitigation effort until the year 2100 could come from CCS.

There are two huge problems though.  The first is that of ‘energy penalty’ – there is a 10 – 40 percent loss of the energy produced by a power station. Wide-scale adoption of CCS may erase efficiency gains of the last 50 years, and increase fossil fuel for power consumption by one third.  Though in theory you could still get 80-90% reductions in  CO2  emissions power costs would rise drastically and you would be increasing the point towards peak coal and peak gas significantly.  It just isn’t a feasible option, at least using current technologies.

But we should give up if you have power stations fed by biomass then with storage you can in theory achieve negative carbon.  That is technology that sucks carbon from the atmosphere and actually reserves global warming.  Ill be writing a lot about these ideas in coming weeks as it requires us to rethink the ideas about how we plan the utility networks in our cities, and the design of our cities; but the prize is great town planning really can save the world.

An alternative to conventional CCS but still embryonic approach is what is known as carbon recycling.  That is making use of the carbon to make things.  It can serve as a fuel and fertilizer foodstock – but there is an intriguing new process – use it to make concrete.

One of the first principles of ecological design is that if you have processes that cause problems with there outputs then avoid those problems by using it as an input into another process – use waste as a resource – form a closed loop process, as in nature.

Consider power stations, high energy input, high carbon output.  What is needed, on the output side of the problem, is a process that needs carbon as an input and would otherwise require vast amounts of energy to extract that carbon from nature.  There is a perfect process concrete.

Concrete is the most widely used material on earth apart from water, with nearly three tons used annually for each man, woman, and child. The manufacture of cement releases a terrifying 9kg of CO2 for every 10kg of cement produced.  Carbon dioxide emissions from a cement plant are divided into two source categories: combustion and calcination. Combustion accounts for approximately 40% and calcination 60% of the total carbon emissions from a cement manufacturing facility.  Estimates of global carbons emissions from concrete  vary between 5-7% of all emissions, but it is one of the fastest growing sectors due to rapid urbanisation and inefficient plants in China.   The impact is mitigated slightly as calcination causes concete to absorb carbon naturally over its lifetime.

Is there a way though to use the natural processes of calcification to extract carbon from power plant emissions?  According to Green Building Elements

California company Calera… is creating cement that actually reduces the amount of CO2 put into the air by power plants. Their location, across the street from a major Californian power plant, siphons smoke stack emissions from the power plant, runs the gas through oil rig or brackish water, and the salts and minerals from the water bond with the carbon dioxide in the gas to precipitate out limestone in much the same way that mother nature does it. What he gets is cement, hard aggregate for making concrete, and water that is already a step toward being purified for drinking thus reducing the time and energy needed to return it to a potable state. The cement can be used just like Portland cement

The process mimics the way corals, shellfish and other deep-sea creatures create their shells and skeletons out of calcium and magnesium in seawater. At the pilot facility, capture rates above 85% of carbon dioxide and SO2 have been achieved for coal combustion.  Also there is no net energy penalty as this is less than the sulphur scrubbers that need to be installed on power stations anyway.  A nice in hard water areas is soft water, as the calcinates that would otherwise fur our kettles are extracted.  Early tests show structural strength similar to conventional Portland cement.

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About andrew lainton

International Urban Planner

Posted on July 19, 2011, in Energy, Sustainable Development, Technology. Bookmark the permalink. 2 Comments.

  1. “initially the IPCC was enthusiastic,
    estimating that between 10% and 55% of the total carbon mitigation effort until
    the year 2100 could come from CCS.”

    Are you saying they’ve changed their position?

    • No there sums were wrong because coal and natural gas would run out in 20 years rather than 40 with CCS. They didnt include an induced consumption effect in their model, their model would never have reached 2100 in any event, it was just a bad model.

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