Carbon-Sucking Concrete to Fight Climate Change

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The construction industry contributes to about 39% of global greenhouse gas emissions, and concrete being an indispensable part of construction, holds an 8% share in it.

Concrete is made using cement mixed with an aggregate - a grainy blend of materials such as stone and sand. After mixing, concrete is poured into a mold and left to harden. The hardened mix is then used for construction purposes. 

While this process doesn’t release any carbon dioxide, the problem lies in the process involving cement production, which releases huge amounts of CO₂.

Many construction companies and suppliers are now using eco-friendly concrete substitutes to keep a check on the environmental impacts of concrete.

Recently, two researchers from the Massachusetts-based Worcester Polytechnic Institute, Suzanne Scarlata and Nima Rahbar, developed a concrete substitute that can remove greenhouse gases from the atmosphere.

The material called enzymatic construction material (ECM) is self-healing and can be used to patch existing concrete.

ECM is composed of carbon anhydrase, an enzyme found in living cells. On reaction with carbon dioxide, it forms calcium carbonate crystals, the main component of ECM.

Other components of ECM are sand slurry and polymer, which act as binding agents. The final mixture is ECM which can remove CO₂ from the air and store it within.

Pros of ECM:

• For 400 lbs of CO₂ produced per cubic yard by concrete, ECM has the potential to absorb 18 lbs of CO₂.
• ECM is more easily recyclable than concrete.
• ECM uses enzymes that are stronger and less risky than the bacteria used in other alternatives of concrete.

Cons: 

• Currently, ECM has a strength of 12 MPa as compared to the strength of Portland cement, which is 20-40 MPa. This makes it unsuitable for building apartments or big structures. As of now, it can only be used for projects that demand a lower load, like the side of a house.
• ECM costs about $168 per yard whole concrete costs about $125 per yard, though the energy costs of ECM (the sum impact of all greenhouse gas emissions attributed to the material across its life cycle) are much lower.

ECM has already been licensed to Enzymatic Inc. for its production as a construction material. The researchers are working on increasing the strength of ECM and improving its resistance to water and humidity to make it more suitable for bigger projects.

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