Most concrete from demolished buildings is simply dumped, much of it illegally. But there’s a better way – and it involves lightning

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At the Shenzhen dump, huge shards of dusty concrete lie in imposing piles. Once the very foundation of this Chinese city, these blocks now seem grotesque in their magnitude, and unsettling in their utter uselessness. Jumbled up with the other relics of modern construction – bricks, wood and steel – and dotted with plastic bags and bottles, it could take centuries, even millennia, for Shenzhen’s discarded concrete to disintegrate back into sand.

China produces more construction waste than any other country - around 2 billion tonnes per year (pdf), or around 4kg per person per day. Two million tonnes of this is concrete. In Shenzhen, which has grown from a town with 30,000 residents to a megacity with 11 million in just 35 years, a full 84% of that construction waste is unceremoniously dumped. It doesn’t even all make its way to official landfills, which don’t have the capacity to handle it, so almost half is disposed in unlicensed sites, or illegally tipped.