Human waste production has multiplied tenfold in the last century. Rubbish – plastic bags, pizza boxes, empty beer cans, tinfoil, bubble wrap, old mattresses, rusty machinery, broken bottles, spent batteries, stale sandwiches, wilting salads and abandoned newsprint – is being generated faster than any other environmental pollutants, including greenhouse gases. And the problem will go on getting bigger until some time in the next century.
Daniel Hoornweg of the University of Ontario and Chris Kennedy of the University of Toronto in Canada and Perinaz Bhada-Tata of Dubai in the United Arab Emirates argue in Nature that the combination of urban growth and material affluence is creating a throwaway problem that won’t go away. The average person in the US throws away his (or her) own body weight in rubbish every month. The detritus linked to modern living has not only grown tenfold in a century; by 2025 it will double again.
Solid waste disposal has become one of any modern city’s biggest costs. Landfill sites near Shanghai, in Rio de Janeiro, and in Mexico City typically receive 10,000 tonnes of waste a day. The world now has more than 2,000 waste incinerators, some able to burn 5,000 tonnes a day, creating attendant problems of ash and air-polluting fumes.
Landfill waste is of course also a notorious source of methane – a potent greenhouse gas – but the authors are primarily concerned with the simple problems posed by the increasing volume of affluent society’s rejected stuff.
It’s a city thing, they say. Country dwellers don’t buy so much packaged food, don’t have factories and don’t throw so much food away. City dwellers on average generate twice as much waste; the more affluent urbanites throw away four times as much.
The three researchers – an expert in energy systems, a civil engineer and an urban waste consultant – say that in 1900 there were 220 million people in the cities. That was 13% of the planet’s population, and these townsfolk produced 300,000 tonnes of discarded stuff every day.
By 2000, there were 2.9 billion people in cities – 49% of the world’s population – creating more than three million tonnes of solid waste per day. By 2025, it will be twice that = enough to fill a line of rubbish trucks 5,000 kilometres long every day.
International idiosyncrasies
Some countries are more profligate than others. Japan’s citizens produce about one third less, per person, than US citizens, even though the gross domestic product per capita is about the same. China’s solid waste generation is expected to go from 520,550 tonnes per day to 1.4 million by 2025.
“As a country becomes richer, the composition of its waste changes,” the authors say. “With more money comes more packaging, imports, electronic waste and broken toys and appliances. The wealth of a country can readily be measured, for example, by how many mobile phones it discards.”
Hoornweg and Bhada-Tata are the authors of a 2012 World Bank report in which they projected a world dustbin collection of 6 million tonnes a day by 2025. They calculate that under a business-as-usual scenario waste will grow with population and affluence as the century wears on, with increasing growth in South Asia and sub-Saharan Africa, and by 2100 it will exceed 11 million tonnes a day and peak sometime in the next century. But this scenario is not inevitable.
“With lower populations, denser, more resource-efficient cities and less consumption (along with higher affluence) the peak could come forward to 2075 and reduce in intensity by more than 25%,” they say. This would save around 2.6 million tonnes per day.
