Saturday, April 21, 2012

Solar-powered Cement Production without Carbon Dioxide Emissions

The global cement industry is currently one of the largest single emitter of carbon dioxide, generating on average about 830 kg of this greenhouse gas for each 1000 kg of cement produced (source: International Energy Agency 2007, Tracking Industrial Energy Efficiency and CO2 Emissions; pdf). Considering that the worldwide annual production of cement is a whopping 3.8 trillion kg (source), the cement industry alone accounts for approximately 5-6% of man-made CO2 emissions.
Conventional thermal decomposition production
of lime (left) versus STEP direct solar conversion of
calcium carbonate to calcium oxide (right) eliminating CO2.

In a previous Nanowerk Spotlight ("New solar-powered process removes CO2 from the air and stores it as solid carbon") we introduced a novel solar conversion process, combining electronic and chemical pathways, for carbon dioxide capture. This STEP (Solar Thermal Electrochemical Production) process proactively converts anthropogenic carbon dioxide generated in burning fossil fuels, as well as eliminates carbon dioxide emissions associated with the generation of metals and bleach. In a subsequent Spotlight ("Reinventing iron production using clean renewable energy instead of coal") we showed how the STEP process could be used as an effective new carbon-dioxide-free process for iron production.

The research team, led by Stuart Licht, a professor of chemistry at George Washington University, has now presented a solar-powered process to produce cement without any carbon dioxide. In a paper (accepted manuscript) in the April 5, 2012 online edition of Chemical Communications ("STEP Cement: Solar Thermal Electrochemical Production of CaO without CO2 emission"), they show that STEP-produced cement operates at solar energy conversion efficiencies higher than that in any solar photovoltaic.

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