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Megacity metabolism: which cities consume more than their fair share?

New York

New York needs to go on a diet, according to a new report that analyses how resources like energy, water and waste pass through different megacity systems.

Scaled on a per capita basis, the largest American city consumed more energy and water, and produced much more solid waste than any of the 27 megacities (populations greater than 10 million) studied.

Tokyo and New York have comparable electricity consumption per capita, however New York fell down due to high use of transportation fuels and heating/industrial fuels. Its solid waste production was also much higher than any other country on absolute and relative terms.

London and Paris, meanwhile, used relatively fewer resources, and Tokyo excelled at water conservation.

Led by engineers at the University of Toronto, and published in the Proceedings of the National Academy of Sciences, the findings could point to strategies to improve city sustainability, the authors of the report said.

“The New York metropolis has 12 million fewer people than Tokyo, yet it uses more energy in total: the equivalent of one oil supertanker every 1.5 days,” University of Toronto civil engineering professor and industrial ecologist Chris Kennedy said. “When I saw that I thought it was just incredible.”

Geography and economic activity played a part in the results, however.

“Wealthy people consume more stuff and ultimately discard more stuff,” Professor Kennedy said.

For example, New Yorkers on average use 24 times as much energy as a citizen from Kolkata, India, and also produce 15 times as much solid waste.

But city-based inefficiencies were also part of the puzzle.

Comparing New York and Tokyo – both rich megacities in temperate environs – the Japanese city won out because of its efficient design and first-rate public transport system, measures which the authors say demonstrates that smart urban policies can reduce resource use, even in the face of rising GDP and growing populations.

Tokyo too has aggressively addressed leaky pipes, a strategy that has reduced water loss to three per cent, compared to over 50 per cent for cities like Rio de Janeiro and Sao Paolo.

“These are places that are really short of water, and yet they’re leaking it away,” Professor Kennedy said.

Professor Kennedy and his team shared several other successful policies, including that:

Moscow has built the largest district heating system in the world, providing combined heat and power to buildings housing 12 million people; this being more efficient that using separate systems for each building

Seoul has developed a system for reclaiming used wastewater for secondary uses like flushing toilets, increasing the overall efficiency of water use

London has been subject to rising electricity costs and taxes on the disposal of solid waste, and it is the only megacity for which per capita electricity use is going down even as GDP goes up

The spread of cities was noted as a factor that influenced energy consumption, with a correlation between per capita electricity use and urbanised area per capita, which was shown to be a consequence of gross building floor area per capita, which is higher in lower-density cities.

The study, while showing the enormous impact of megacities on energy, water and waste, also suggested that as megacities proliferated, smart policy decisions could make an impact on resource use.

“What we’re talking about are not short-term, one-election issues, but long-term policies on infrastructure that shape cities over years or decades,” Professor Kennedy said.

“The evidence is that megacities can make some progress in reducing overall resource use, and I think that’s encouraging.”

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