After water, concrete is the most widely used substance on the planet. But its benefits mask enormous dangers to the planet, to human health – and to culture itself
Taking in all stages of production, concrete is said to be responsible for 4-8% of the world’s CO2. Among materials, only coal, oil and gas are a greater source of greenhouse gases. Half of concrete’s CO2 emissions are created during the manufacture of clinker, the most-energy intensive part of the cement-making process.
But other environmental impacts are far less well understood. Concrete is a thirsty behemoth, sucking up almost a 10th of the world’s industrial water use. This often strains supplies for drinking and irrigation, because 75% of this consumption is in drought and water-stressed regions. In cities, concrete also adds to the heat-island effect by absorbing the warmth of the sun and trapping gases from car exhausts and air-conditioner units – though it is, at least, better than darker asphalt.
It also worsens the problem of silicosis and other respiratory diseases. The dust from wind-blown stocks and mixers contributes as much as 10% of the coarse particulate matter that chokes Delhi, where researchers found in 2015that the air pollution index at all of the 19 biggest construction sites exceeded safe levels by at least three times. Limestone quarries and cement factories are also often pollution sources, along with the trucks that ferry materials between them and building sites. At this scale, even the acquisition of sand can be catastrophic – destroying so many of the world’s beaches and river courses that this form of mining is now increasingly run by organised crime gangs and associated with murderous violence.