Concrete is an incredibly versatile and widely used material in construction. And let's be honest; we humans love it. We love the look, the feel, and all possible ways to use it. It is no wonder that our cities are full of it. From buildings and bridges to roads and dams, concrete plays a significant role in shaping our modern infrastructure.

However, while it may be solid, durable, and nice to look at, concrete has a dark side regarding its environmental impact. In this short article, we will explore the harmful effects of concrete and its high carbon footprint.

Carbon Dioxide Emissions

One of the major concerns associated with concrete is its significant contribution to greenhouse gas emissions, primarily carbon dioxide (CO2). Manufacturing cement, a key component of concrete, involves heating limestone and other materials to high temperatures, releasing large amounts of CO2 into the atmosphere. It is estimated that cement production accounts for around 8% of global CO2 emissions, making it a substantial contributor to climate change.
If the concrete & cement industry were a country, it would be the world's fourth-largest emitter, releasing almost as much CO2 as India.

Clima-Killer Cement
What is concrete made of? Concrete is primarily composed of sand, which accounts for approximately 78 percent. This is followed by cement, water, and other additives at 14, 7, and 1 percent respectively. Although cement only accounts for approx. 14% of the building material, approx. 90% of CO2 emissions are caused by cement. Sand, on the other hand, the primary ingredient of concrete (78%) only accounts for approx. 7% of its CO2 emissions.

Energy Consumption

Producing concrete requires vast amounts of energy. The entire production process is energy-intensive, from mining and processing raw materials to transporting and mixing them. The extraction of limestone and other aggregates and the operation of kilns and machinery consume substantial amounts of fossil fuels. This reliance on non-renewable energy sources further contributes to environmental degradation and climate change.

Land Degradation

The extraction of raw materials for concrete production, such as sand, gravel, and limestone, often involves the destruction of natural habitats. Mining activities can disrupt ecosystems, harm wildlife, and damage delicate ecosystems like rivers and streams. Additionally, the extraction of sand, a critical component of concrete, has led to sand scarcity and illegal sand mining in many regions, exacerbating environmental problems

Water Consumption

Concrete manufacturing also consumes vast amounts of water. It is estimated that concrete production currently accounts for almost 9% of global industrial water use. Mixing requires water to hydrate the cement, ensuring proper curing and strength. Moreover, mining activities associated with obtaining aggregates can deplete water sources, leading to water scarcity and ecological imbalances. This is particularly concerning in regions already facing water stress and where concrete production is extensive.

Waste Generation

Concrete production generates a significant amount of waste. Construction sites produce surplus concrete, commonly called "concrete waste" or "concrete washout." If not handled properly, this waste can end up in rivers or landfills, causing pollution and environmental harm. Additionally, the demolition and disposal of concrete structures contribute to construction waste, adding to landfill volumes.

Urban Heat Island Effect

Concrete's high heat-absorbing capacity contributes to the urban heat island effect. Metropolitan areas with extensive concrete infrastructure tend to absorb and retain heat, leading to increased temperatures compared to surrounding rural areas. This phenomenon exacerbates the impacts of heatwaves, affects human health, and increases energy demands for cooling buildings, further straining the environment.

Mitigating the Negative Effects

However, let us not bury our heads in the sand! So many excellent alternative construction materials can easily compete with our beloved concrete. We have portrayed some of them in our journal and project page, such as clay, timber, and hemp.

Further, we see many innovations in this sector popping up. For instance, a couple of companies and scientists have made it their mission to tackle the carbon footprint of concrete. For example, the California-based company Brimstone is developing the first carbon-negative cement by using calcium silicate rocks instead of limestone to produce the cement. Other innovators try to tackle water usage and waste production. That sounds exciting, but only the future will tell if they succeed.

Sources

Monteiro, P., Miller, S. & Horvath, A. Towards sustainable concrete. Nature Mater 16, 698–699 (2017). https://doi.org/10.1038/nmat4930

Miller, S. A. (2020, October 5). Impacts of booming concrete production on water resources worldwide. Sustainability Community. https://sustainabilitycommunity.springernature.com/posts/29627-impacts-of-booming-concrete-production-on-water-resources-worldwide

Rouhi Broujeni, B., Omrani, G. A., Naghavi, R., & Afraseyabi, S. S. (2016). Construction and Demolition Waste Management (Tehran Case Study). Engineering, Technology & Applied Science Research, 6(6), 1249–1252. https://doi.org/10.5281/zenodo.225510

Beiser, V. (2019, August 20). Concrete is the reason cities are hotter than rural areas. Time. https://time.com/5655074/concrete-urban-heat/

Tracy, B., & Novak, A. (2023, January 22). Cement industry accounts for about 8% of CO2 emissions. One startup seeks to change that. CBS News. https://www.cbsnews.com/news/cement-industry-co2-emissions-climate-change-brimstone/