Pollution Talks With Hui

When talking about urbanisation, the mental image that comes to mind would most likely be forests and greenery being replaced by concrete buildings and asphalt roads. In the midst of creation of such an urban image, the construction industry plays one of the main roles. The construction sector accounts for around 23% of global air pollution, 50% of the climatic change, 40% of drinking water pollution, and 50% of landfill wastes (Go Contractor, 2017). Every aspect of construction poses clear environmental implications. For this blog post, we place focus on the production of concrete, a vital material in building construction.

Cement and concrete

Concrete is produced mainly through the use of three main materials; the aggregate, a binder and water. Aggregates used are usually cheaper options such as gravel or sand, and binders used are cement. Due to its low cost and relatively common material components, basic concrete production utilises Portland cement, created by heating limestone with clay. As Portland concrete is a form of hydraulic cement, it only starts to solidify under the presence of water. As such, concrete can be casted into moulds to form desired shapes by mixing all three components together.

Environmental implications

Through the explanation of concrete production, we can identify a few aspects in which concrete production poses environmental or pollution issues. Firstly, the extraction of aggregates and base materials for cement is hugely pollutive. Mining activities are frequently coupled with immense air, land and water pollution. The transportation of the heavy aggregates to and from the mines also contribute significantly to air pollution (Pal & Mandal, 2021). Next, we see that concrete production can be an extremely thirsty activity, requiring large amount of water during its mixing stages. Lastly, we see that cement production is a large source of carbon emissions due to its production requiring large amount of fuel for the heating process. An estimate 8% of human global carbon emissions come from cement production alone (Nature, 2021).

Greener alternatives?

With increasing pressures to cut back on carbon emissions in the recent times, green alternatives have been gaining traction. Green cement refers to any forms of cement with aims of using a carbon-negative manufacturing process. This can be done through the use of recycled cement or concrete, or even this interesting one currently being refined by a group of researchers from the University of Edinburgh, who looks to bypass the intense heating process of cement production through the use of a bacteria and urine. With better technology, we can definitely look forward to a future with greener buildings, both in and out.

References

Concrete needs to lose its colossal carbon footprint. (2021). Nature, 597(7878), 593–594. https://doi.org/10.1038/d41586-021-02612-5

Pal, S., & Mandal, I. (2021). Impacts of stone mining and crushing on environmental health in Dwarka river basin. Geocarto International, 36(4), 392–420. https://doi.org/10.1080/10106049.2019.1597390