The built environment is awash with waste. From consumer packaging and uneaten food to construction waste, the human race has become addicted to throwing stuff away. In rich countries, because we throw more away, we are also trying to export more of it. But even that model now seems unsustainable. China recently stopped importing most American recycling, leading to rapidly growing mountains of garbage in many US cities. And although the UK has significantly increased the amount it recycles over recent decades, population growth means that overall volumes of waste are likely to continue to increase.

Where I live in Uganda the amount of waste that individuals produce is relatively small but, because of poor collection and processing infrastructure, the visible problem often appears much worse than in the UK. Most plastic food and drinks packaging is simply thrown to the ground. Roadsides across the country are littered with bottles and wrappers. In a few affluent parts of Kampala, this is swept up and collected. But in most parts of the city, piles of plastic appear over the course of the day, which are then set alight as dusk falls. These low-intensity fires fill the air with noxious smoke, making Kampala, by some measures, one of the most polluted cities in Africa.

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