Boston startup to develop low-carbon cement tech

Bloomberg

Boston-based startup Sublime Systems has raised $40 million to develop a new technology to produce low-carbon cement.
The cement industry contributes as much as 8% to global emissions of planet-warming carbon dioxide. Meeting global climate goals under the Paris Agreement would require reducing that to zero within decades.
However, cement has proven to be one of the more difficult sectors to clean up because manufacturing low-carbon cement using the existing processes is much more expensive than producing the conventional equivalent.
The other major difficulty is that cement’s emissions aren’t just about the fossil fuels burned in the production process. Most cement today is made by throwing limestone and sand in a coal-fired kiln, which produces planet-warming gases. Even if the coal is replaced by a clean-energy source, limestone’s chemistry means that significant amounts of carbon dioxide will still be released.
The solution that has gained most traction among large cement companies seeking to reduce emissions is to build carbon-capture units, which trap carbon dioxide released from their plants before it enters the atmosphere. However, the process is energy intensive and can more than double the cost of the end product.
Sublime says it has come up with a process that cuts both energy use and carbon emissions. The invention was made in the laboratory of serial-entrepreneur Yet-Ming Chiang, who is also a professor at the Massachusetts Institute of Technology. The latest round of investment came from Lowercarbon Capital, along with previous investors Energy Impact Partners and MIT’s The Engine. Sublime also signed on Siam Cement Group, a southeast Asian company, as a strategic investor.
Sublime’s solution involves splitting the cement-making process into two steps. The first step is to make calcium in a form that’s ready to chemically react with silicon—the key element in sand.