The world’s first carbon negative portland cement

A new process for manufacturing cement uses calcium silicate rocks instead of limestone

Spotted: Concrete is the most widely used manufactured material on the planet and cement is its key ingredient. More than four billion tonnes of the material are used globally every year, generating around 2.5 billion tonnes of carbon dioxide (CO2) annually – about eight per cent of the global total. Cement production is so energy intensive because it uses enormous kilns that are continuously heated to around 1,500 degrees Celsius. This high heat powers the process that turns limestone (CaCO3) and clay into cement, but it also releases high levels of CO2.

Startup Brimstone is hoping to change this with a process that produces an identical product to conventionally manufactured cement, but without releasing CO2. Brimstone accomplishes this by sourcing lime (CaO) from calcium silicate rocks instead of limestone. The calcium silicate rocks do not contain embedded CO2, so do not release the gas as a waste by-product. The process also produces magnesium species as a waste product. This passively absorbs CO2, making the entire process net carbon negative, even when accounting for the fuel used.

Carmichael Roberts of Brimstone investor Breakthrough Energy Ventures, points out that, “Not only has Brimstone figured out a way to eliminate the [CO2] emissions in [the cement manufacturing] process – [its] innovation creates an opportunity where our built environment could be a net sink for carbon. This means that the buildings and bridges that we build with carbon negative Brimstone Portland Cement can be a part of the climate solution instead of the intractable liability they are today.”

Springwise has spotted a wide range of other innovations reducing the impact of concrete use, such as making concrete blocks using unrecyclable plastic, and using AI to make the use of concrete more efficient.

Written By: Lisa Magloff