Amidst all the negative news that we were bombarded with during the COVID pandemic, a few positives that emerged were the significant improvement in air quality and other environmental parameters due to the prolonged lockdowns. The world came to a grinding halt, which while causing great economic distress also highlighted the extent of pollution that the so-called ‘daily routine businesses’ were causing. The negative effect of human activity on the environment was truly driven home.
In recent times, there is growing agreement about the dangers of global warming. Incidences of extreme weather events and many other tell-tale signs have established beyond doubt that man has gone too far in causing serious damage to the environment. Unfortunately, there is still no consensus amongst nations about sharing the responsibility and efforts required to mitigate and hopefully eventually reverse the damage.
In this context, we must all examine the environmental damage that our own businesses cause and take steps to minimize it. The construction industry, unfortunately, is a big contributor to this damage and we must grab this opportunity for course correction. The most common metric for measuring the environmental impact of any activity is its carbon footprint. In essence, we need to be aware of the carbon footprint of construction and take action to minimize it. While the carbon footprint of using a building (O&M phase) is also significant, the focus in this article is on the construction phase.
The carbon footprint of construction primarily comes from the energy consumed in producing the materials used, their transportation to the project site, and creating the structure using the construction materials. While there are many different materials used in construction, the two most widely used (and also most consumed) materials are cement (primarily through concrete) and steel.
The carbon footprint is expressed in terms of CO2e, where the CO2e is a sum of fossil-based emissions calculated with help of IPPC weighting factors (for 100 years). For the record, approximate value of the carbon value of CO2e of different construction materials is listed below in descending order. It should be borne in mind that the values are expressed in gms of CO2e per kg of material consumed. Therefore, the total weight of alternative materials required to provide the same function should be assessed in order to get a true picture about the carbon footprint of the competing/alternate materials. For example, though the carbon footprint of steel is the highest in this list, the per kg consumption of steel is much lower than concrete and other materials. As far as concrete is concerned, CO2e increases for grade of concrete (cement consumption), though the relationship is not linear and depends on other features like workability and use of supplementary cementitious materials.
CO2e in gms/Kg
M 20 concrete
CO2e of various materials
It would be worth exploring what decisions and actions contribute to the consumption of steel and concrete in construction and what can be done about it.
The following broad categories of actions determine the carbon footprint of construction when viewed from the narrow perspective of consumption of steel and concrete.
The last four actionable aspects are in the domain of construction. Therefore, here is a short list of what we could and should do about it.
This is just a small step towards bringing in awareness about a vast subject. With contribution from all stakeholders, we can help reduce our contribution to the problem of environmental damage.