Concrete is one of the most important materials we have. Without it, our lives would be totally different. It is the most widely used construction material in the world, and for good reason. It is cheap, yet also durable, versatile, inflammable, and weatherproof, and it has made many of humanity’s creations possible. Because of this, concrete production continues to increase, especially in developing countries. There are three tons of concrete for every person on Earth, and if growth trends continue, over the next 40 years we will use enough concrete to build the equivalent of New York City every month! Sadly, like many things, this comes at a great environmental cost.
Concrete is made of gravel, sand, water, and cement. The cement is the part with the environmental drawbacks. Cement is a blend of mostly limestone and some clays. The cement is made by heating this compound to release the calcium oxide in the limestone. Calcium oxide is essential to concrete as it holds the gravel, sand, and water in cement together. The problem is that you need heat to get the calcium oxide, and limestone and heat make carbon dioxide as well as calcium oxide. There is no way to make cement without also creating carbon dioxide, and since the carbon dioxide has no use in the rest of the process, it is released into the atmosphere. That being said, this only accounts for half of concrete’s carbon dioxide emissions. 40% of its emissions are released when fossil fuels are burned to create the large amounts of energy required to heat the limestone enough to obtain the calcium carbonate. The final 10% of emissions come from mining and transporting the materials. For every ton of cement made, a ton of carbon dioxide is released into the atmosphere. These processes, as well as growing concrete production, makes concrete responsible for 8% of all carbon emissions worldwide. But what can we do?
Firstly, It is necessary to electrify the heating process of making cement and reduce emissions from concrete’s transportation. There are many ideas about the rest of the concrete process and how to reduce emissions there. Some groups are trying to figure out how concrete can repair itself so it does not have to be replaced as often. This is a good idea, but it is not the solution to this problem because most of the concrete being made is not being made for repairs, but for building new structures. Another solution is implementing carbon capture processes into the concrete production process, but this is still expensive and inefficient, and cannot yet be implemented across the globe. Another innovation is using carbon dioxide instead of water to harden the concrete blocks, which reduces carbon dioxide emissions and saves precious water. An additional solution on the horizon is to grow cement from bacterias, thus cutting down on emissions from the cement production process of making concrete. None of these ideas have been tested on a large scale, and it will take some time before they are widespread, but innovation is happening, which is what matters.