Solar Thermal Heat Method Produces Cement with Zero CO2 Emissions

Cement production is one of the largest emitters of greenhouse gases, second only to coal-powered electricity. More than 3 billion tons of cement was consumed globally in 2010 alone, the production of which caused environmental damage at all stages including airborne dust and gas pollution and injury to land areas from quarrying.

St. Mary's Cement Plant, Charlevoix, Mich.

But according to a recent study in Chemical Communications, researchers from Virginia's George Washington University have developed a method for cement production that relies on solar thermal heat to eliminate CO2 emissions. The scientists believe the process will also be cheaper than current production techniques.

The research team explained that 60 to 70 percent of CO2 emissions during cement production occur during the conversion of limestone into lime. CO2 is a byproduct of the conversion process. The remaining emissions come from burning fossil fuels to heat the reactors used during the conversion.

The new method would eliminate CO2 from both processes using solar thermal technology. First, solar heat would assist in an electrolysis method of separating the lime from the limestone. Instead of producing carbon dioxide, as in current methods, the new process would produce only oxygen and graphite. The graphite could be stored as solid carbon, researchers said, and by separating it from oxygen atoms, it no longer poses a threat to the atmosphere. Solar thermal heat would additionally replace the fossil fuel heat sources currently in use.

The study estimates that the new method could also be cheaper than current lime production techniques because carbon monoxide produced during the high temperature reaction can be sold and used in other industries.

As an added benefit, researchers said the new solar thermal method isn't limited to cement production. Any industrial application that converts limestone to lime, such as purifying iron, producing glass, paper and sugar, softening water and removing phosphates from sewage, can take advantage of the technology.