How PropTech Is Trying to Limit Concrete Carbon Emissions

CRE has to deal with carbon emissions. Regulations want it. Investors want it. Tenants want it. “Cement production is currently the largest single industrial emitter of CO2, accounting for ∼8% (2.8 Gtons/y) of global CO2 emissions,” wrote M.I.T. researchers in a 2019 paper.

Why is cement such a culprit? Fossil fuel. The process requires heating limestone to about 1,500 degrees Fahrenheit, at which point you get calcium oxide — the desired material — and carbon dioxide — the greenhouse gas. Then you need to heat clay to between 2,550 and 2.700 degrees to create aluminum oxide, silicon dioxide, and iron oxide. The oxides together make Portland cement and even more CO2.

Something’s got to give, and researchers and companies have been looking at many ways to reduce the emissions, often by looking at how to extend cement with other materials to reduce the amount used in concrete without losing significant strength. Sometimes this is attempted through how materials are processed. Those M.I.T researchers were working on using an electrochemical process to manipulate pH values to separate materials, sequester carbon dioxide, and produce hydrogen and oxygen to generate electrical power for heat.

Others treat minerals at much lower temperatures to create a material that can replace a significant percentage of cement. Doctor Carlos Fernandez, chief chemical engineer of materials at the Pacific Northwest National Laboratory, has developed self-reinforcing and self-healing cement that incorporates waste plastic fibers that can fix cracks within 24 hours of when they occur. That could alleviate a lot of repairs and replacements.

Carbon Limit is a company with a commercially available pour-in additive that they claim can permanently remove carbon dioxide from the air and lock it into a structure. It combines “Direct Air Capture (DAC) technology with CO2 mineralization to reduce the carbon footprint of concrete significantly. The stored CO2 is thermodynamically stable as there is no reversal of the process unless the concrete is incinerated at temperatures of 550 degrees Celsius (1,022 degrees Fahrenheit). Carbon capture and sequestration in concrete using CaptureCrete can reach as much as 100kg of CO2 per ton of concrete; and in total could potentially reduce concrete’s CO2 by as much as 75%.”

Developers looking to gain competitive market positions will have to begin looking at such technologies to find economical ways to improve greenhouse gas management.