To raise awareness, Extinction Rebellion staged a good-humoured protest in Paris, engaging with employees of two giant cement producers, handing out fruit and explaining their points of view. rances Cowell considers some reasons why cement is so damaging to our world.
Stroll around any European city and compare the ugliness of many rain-streaked, concrete-clad buildings with the rain-streak-free elegance of many pre-war stone-clad edifices. Its as if concrete, more than, say, limestone or granite, invites a sort of architectural laziness.
It’s in the mix
While many concrete buildings have undeniable architectural and functional merit: think the Sydney Opera House (clad in ceramic tiles, but concrete underneath) and the graceful lines of Waterloo Bridge in London, most don’t. But, aside from aesthetics, there are other big problems with concrete and cement, its main ingredient.
Cement production is the third largest source of the carbon dioxide we send each year into our atmosphere. Hardly surprising when you think about how much of it is produced. In 2019, China alone consumed 2,200 million metric tons of cement, up from near zero at the start of the 1980s. By comparison, the USA routinely consumes about 89 million metric tons a year.
Its hard to find something good to say about concrete: its every aspect wreaks havoc on the environment, from mining its ingredients, transporting them, making them into cement, transporting the cement and using it to build things.
Cement is made from limestone, river sand and, typically, clay, all of which need to be mined and mixed, all with environmental costs. Perhaps surprisingly, sand is the big problem. Sand-mining has a lot in common with logging. While sea sand is plentiful, it is both hard to get at and mostly too coarse and full of impurities, so cement-makers prefer river sand. It too may seem ubiquitous, and it once was. But river-beds around the world have been depleted so much that whole ecosystems have disintegrated, with knock-on effects for the world’s food chain. And that’s not to mention the collapsed riverside buildings and hundreds of millions of people whose livelihoods have been destroyed. Like illegal logging, official efforts to curb it are ignored, circumvented with bribes – which make the practice lucrative for officials as well as sand thieves – and worse. Communities that have lived off river systems for centuries are swept aside in the stampede for sandy lucre.
When the sand, limestone and clay have been harvested, they are transported – using fossil fuels of course – and are combined in an extraordinarily energy-hungry process. Cement production alone consumes about ten percent of the global energy budget, according to VDZ, a German industry association. Transporting the cement to where it will be used belches yet more carbon into the atmosphere and toxic particles into lungs.
No long term benefit
Even the “constructive” part of concrete is bad. Look at those ugly post-war blocks and bear in mind that their economic life is calibrated in decades, whereas the granite or limestone buildings before them could last centuries, even millennia. Concrete is brittle: to make it strong enough to support a building it is reinforced with steel rods. Over time, tiny fissures form in the concrete that let water in, which rusts the steel rods, expanding as they do and causing the concrete to crack and flake, a process known as palling. Have you ever noticed that concrete buildings near the beach, more than elsewhere, are often cracked and streaked with rust? That’s because the humid sea air accelerates palling. Maintenance is expensive and eventually no longer worthwhile, so the building is demolished when it is only decades old, and the cycle starts again. You may breathe a sigh of relief to see the eyesore come down, but you shouldn’t be. You should ask what will happen to all that useless grey stuff? Landfill. And it will be replaced by more grey stuff made from river sand in the same environmentally catastrophic process. What will rise in its place is not guaranteed to be any prettier. And on it goes.
In poorer countries, the story is even worse, for at least four reasons. First, lacking educated and concerned protesters and a lively press to defend those poor riparian communities and the environment on which they depend, they are more likely to have their river bed gouged. Second, they are a bit more likely to have local officials on the take, who then champion, rather than discourage, sand-mining, flaunt laws and suppress any protests. Third, the concrete monstrosities replace buildings made of local, more practical materials. Remember the earthquake and tsunami that hit coasts in South East Asia in 2004? Bamboo villages on the south coast of Sumatra and elsewhere flattened by giant waves were rebuilt with concrete. Lucrative for some, expensive and dangerous for everyone else. Bamboo that has withstood centuries of high wind and earthquakes is cheap, flexible, low maintenance and durable. When the wind blows or the earth moves, it bends. If it falls down, its not likely to kill you, as concrete does, and you can rebuild it quickly and cheaply using local materials. Which brings us to the fourth problem with concrete in poor countries: they are much more likely to suffer high winds and earthquakes than most rich countries – and less likely to have robust standards of construction quality, so the concrete buildings that rise are often shoddier still.
What’s the alternative?
The folk at extinction rebellion understand that if you’re going to get rid of concrete and cement, you have to find a viable alternative. Yet its hard to imagine a bamboo skyscraper, for example. Timber can now be built up to many stories, but not as high as concrete, while steel is only a bit less environmentally damaging. Interestingly, some see hope in a revival of stone (in solid slab, form, as opposed to minced up and mixed into cement), which advocates argue can be significantly cheaper and less carbon-emitting than either concrete or steel and can support structures of up to 30 storeys. Progressive architects and town planners will be watching closely. Wood, steel and stone are all more durable than concrete – and usually look better.
Science, too, is coming to the rescue, with innovative and increasingly competitive alternatives to cement and concrete. But they are held back by a mixture of building designs that default to concrete, and building standards that tend to centre on concrete. Around the world, and even within the EU, building standards are fragmented, which makes it hard for innovative firms that might offer realistic alternatives to establish the economies of scale they need to challenge the dominance of concrete.
Sensible government policy can speed up the process with coordinated building standards that remove some of the uncertainty of launching a whole new technology. The competitive environment can also be made fairer too. One reason there is so much concrete about is that the architects, builders and developers of the buildings do not bear the costs that concrete imposes on everyone else. A tax on concrete use that reflected its true cost throughout its life to the environment and the atmosphere would achieve two things. First it would impel architects and developers to look into other solutions. Taxes can be structured in such a way that they encourage cement and concrete producers to explore more efficient ways of making cement and less polluting ways of transporting them. A cement tax would reduce or remove altogether the implicit subsidy now enjoyed by cement and concrete producers in not bearing the full costs associated with their products. That would make it easier for newer – and older, more practical materials to gain a foothold – in much the same way that temporary subsidies for wind and solar electricity generation helped renewable energy sources to challenge fossil fuels.
A bit of innovation in building materials seems long-overdue and will be very welcome. It might even look a bit better.