All developed cities today in our world depend on one thing: concrete. Nowadays, our planet is covered in concrete to such an extent that it is the second most human-used material after water. Indeed, it is extremely useful, providing solidity, stability, and durability to our constructions, but this invention praised for its indestructible nature is more destructive than you’d think. The industry bears a hidden aspect; it accounts for approximately 8% of global CO2 emissions.
Not only is its creation highly polluting, relying on sand quarries that damage biodiversity and release a lot of particles, but once installed, concrete causes significant water loss and, above all, generates a tremendous amount of heat. In fact, asphalt concrete traditionally used in most countries, is black and thus absorbs solar radiation, capturing energy in the form of heat, instead of reflecting it back towards the atmosphere. This phenomenon can be measured quantitatively through the Albedo effect (the ability of a surface to reflect sunlight on a scale from 0 to 1).
Knowing this, one would think a very simple solution would be changing the colour of all of our roads, replacing black with a colour with a higher Albedo. Some cities such as Doha, Los Angeles and Geneva, have been experimenting with the use of blue or white asphalts called “cool” pavement technologies. The aim of these is to reduce the surface temperature of roads, thus preventing the formation of urban heat islands. This solution can be quite expensive as it would mean changing much of the existing infrastructure, but, some entrepreneurs have developed products with the same benefits as ‘cool’ pavements, that are applied by coating pre-existing roads.
Depaving cities would be another viable and cheaper option. It simply consists of replacing concrete or asphalt with ‘porous’ permeable pavements, such as soil, woodchips or even traditional Roman cobblestones. These all allow better drainage as water can infiltrate directly into the earth, maybe even helping solve flooding issues which are likely to become more frequent due to climate change. Plants and trees could also be coupled with these types of pavement, resulting in greener cities (both literally and figuratively) with better air quality, heat-island regulation and better aesthetics!
Covering our planet with concrete is arguably one of the worst things we have done for its environment and ecosystems. Today, we already have alternative technologies and solutions to reduce and replace this polluting material. It is thus imperative to exploit these at local and regional levels, developing green and resilient urban spaces and turning away from the cement industry.
Photo by Andrei Slobtsov on Unsplash