MIT researchers find new approach suggesting path to emissions-free cement

cement is the world’s leading construction material — but did you know producing it is one of the major sources of greenhouse gas emissions accounting for about 8 percent of all such releases? this means that if cement production were a country, it would be the world’s third-largest emitter. aiming to solve this problem, a team of researches at MIT has come up with a new way of manufacturing emission-free cement that could eliminate the total emissions while also making other useful products in the process.

in a demonstration of the basic chemical reactions used in the new process, electrolysis takes place in neutral water. dyes show how acid (pink) and base (purple) are produced at the positive and negative electrodes. a variation of this process can be used to convert calcium carbonate (CaCO3) into calcium hydroxide (Ca(OH)2), which can then be used to make portland cement without producing any greenhouse gas emissions. cement production currently causes 8 percent of global carbon emissions.
image by felice frankel

‘about 1 kilogram of carbon dioxide is released for every kilogram of cement made today,’ comments yet-ming chiang the kyocera professor of materials science and engineering at MIT. ‘that adds up to 3 to 4 gigatons (billions of tons) of cement, and of carbon dioxide emissions, produced annually today, and that amount is projected to grow. the number of buildings worldwide is expected to double by 2060, which is equivalent to “building one new new york city every 30 days,’ he says. and the commodity is now very cheap to produce: it costs only about 13 cents per kilogram, which he says makes it cheaper than bottled water.

time-lapse video of the decarbonation cell containing pH indicator dye. this decarbonation cell starts at pH 6, as indicated by the yellow color, and has no separators. calcium carbonate powder has been placed at the bottom of the left chamber.

cement is made by grinding limestone and then cooking it with sand and clay at high heat, which is produced by burning coal. this process generates carbon dioxide from the burning of the coal and from the gases released from the limestone. the new process created by chiang would eliminate or drastically reduce the emissions by first, eliminating fossil fuels from the heating process by exchanging them with clean, renewable energy. then, it would use an electrolyzer to dissolve the limestone.

time-lapse video of the decarbonation cell containing pH indicator dye. porous paper separators have been placed in front of each electrode. B, and CaCO₃ powder in a cup surrounding the OER electrode on the left.

‘in their laboratory demonstration, the team carried out the key electrochemical steps required, producing lime from the calcium carbonate, but on a small scale,’ reports MIT news. ‘the process looks a bit like shaking a snow-globe, as it produces a flurry of suspended white particles inside the glass container as the lime precipitates out of the solution.’

project info:

name: emissions-free cement

developed by: researchers at MIT