Massachusetts Institute of Technology (MIT) researchers in Cambridge, Massachusetts, have found a way to eliminate carbon emissions from cement production, a major source of greenhouse gases (GHGs).
The production of cement accounts for about eight percent of all GHGs. MIT researchers have come up with a new way of manufacturing that could eliminate emissions altogether, and could even make some other useful products in the process. They offer the idea of using an electrochemical process to replace the current fossil-fuel-dependent system.
Ordinary Portland cement is made by grinding up limestone and then cooking it with sand and clay at high heat, which is produced by burning coal. The process produces carbon dioxide (CO2).
Firstly, the new approach could eliminate the use of fossil fuels for the heating process, substituting electricity generated from clean, renewable sources. Additionally, the new process produces the same cement product.
The new process centers on the use of an electrolyzer where a battery is hooked up to two electrodes in a glass of water, producing bubbles of oxygen from one electrode and bubbles of hydrogen from the other as the electricity splits the water molecules into their constituent atoms. Importantly, the electrolyzer’s oxygen-evolving electrode produces acid, while the hydrogen-evolving electrode produces a base.
In the new process, the pulverized limestone is dissolved in the acid at one electrode and high-purity CO2 is released, while calcium hydroxide, generally known as lime, precipitates out as a solid at the other. The calcium hydroxide can then be processed in another step to produce the cement, which is mostly calcium silicate.
The CO2, in the form of a pure, concentrated stream, can then be easily sequestered, harnessed to produce value-added products such as a liquid fuel to replace gasoline, or used for applications such as oil recovery or even in carbonated beverages and dry ice. The result is that no CO2 is released to the environment from the entire process, says Yet-Ming Chiang, one of the researchers.
Though they have demonstrated the basic electrochemical process in the lab, the process will require more work to measure up to industrial scale.