"Solid waste is an incredibly useful proxy for total global impact," said Daniel Hoornweg of the University of Ontario Institute of Technology, who published a commentary on the issue in Wednesday's edition of the science journal Nature.
"This paper is basically saying that we're on track to triple the impact — the global damage — to the planet. Arguably, the planet's having a pretty hard time today dealing with the damage that we're inflicting on it."
Hoornweg says the amount of garbage a society generates depends to a large extent on how rich its members are.
As wealth grows, so does trash — up to a point where garbage per capita tends to level out no matter how much richer everyone gets. That's because people tend to shift from buying stuff, which creates trash, to buying experiences, which doesn't.
As well, wealthy societies tend to curb their waste, Hoornweg writes.
While North American and European cities have already reached that point, global trash growth is now being powered by rising wealth in the cities of Asia. Eventually, African cities will be the driver.
Hoornweg says the 2.9 billion people living in cities generated three million tonnes of solid waste a day. By 2025, it will be double that — enough to fill a line of garbage trucks 5,000 kilometres long.
Just as peak oil theorists suggest that oil production will eventually reach a maximum, Hoornweg says the same thing will happen to trash.
But even if significant measures are taken to curb global resource consumption, that point isn't likely to be reached until all the way out to some time between 2110 and 2120. That will be well over 11 million tonnes of trash, every single day.
The problem is not so much the garbage itself, said Hoornweg, but the resources used to create that much trash.
"It's not so much the environmental impact of that collection and disposal. It's much more what that represents upstream — how many trees were cut, how many rivers were polluted, how much energy went into all of that waste."
Using United Nations calculations on how much impact the planet can stand, Hoornweg figures peak trash needs to happen by 2075.
The answer isn't to curb urban growth, he said. Cities can actually be more environmentally friendly than rural areas. Besides, urban growth is likely unstoppable.
"It isn't good enough just to build cities," said Hoornweg. "You have to build the right city — dense, resilient, equitable. I would throw in 'kind' as well, although we're not allowed to talk about that as scientists."
Too much inequity, he said, creates instability.
"Sustainability has to have a bare minimum of equity."
Societies have to learn to see their productive capacity as part of a web, Hoornweg said.
"Composting, waste minimization, industrial ecology, where you try and get one industry to use the waste of another industry and try to create some sort of urban metabolism."
Garbage is a lens through which we can understand how close we are to a environmentally sustainable future, said Hoornweg.
"I don't think we're going to get to sustainability because we think it'll generate less waste. But I think it's a pretty powerful argument that there's so many benefits getting to a more sustainable trajectory that this is just one more."
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