Universiteit Leiden

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What global cities are made of

Understanding what our buildings and cities are made of is an important step in making them more sustainable. Industrial ecologist Tomer Fishman (CML) has received an ERC Starting Grant to map the construction materials used in buildings in the Global South. 'Without the data, you can't formulate policy.'

Approximately half of the materials humans extract from nature every year are used for construction materials. Think of cement, concrete, steel and wood. Producing all these materials emits 15 percent of the annual greenhouse gases.

And when buildings reach the end of their life or require renovation, we are left with these same materials. Fishman points to the thousands of waste containers you see around the Netherlands in front of houses undergoing renovation. 'Where do they go?

Lack of data for the Global South

In other words, how we construct buildings and what materials we use has a big impact on the environment. By making it more sustainably and eco-friendly, enormous benefits can be achieved.

The greatest obstacle is a lack of data. This is especially true for the Global South. 'By now, we have quite good statistics on materials used in buildings in Europe, the US, Australia, and even China.' Part of this is thanks to Fishman's own prior research.

From ‘ad hoc’ to structural

But in most countries, there is almost no information on what buildings and cities are made of. While these emerging countries are exactly where most of the future growth will take place. 'And without data, you can't formulate policy,' Fishman says. He compares it to CO2 emissions. 'You need to know how many emissions there are in order to plan how to reduce them.'

The ERC grant enables Fishman to gather data in what he calls an 'all-in structured project,' instead of the 'ad hoc' research that has taken place so far. The project’s full name is ‘Materials-GRoWL: Gauging the Rest-of-the-World’s Lifecycles of construction materials’, with the Rest of the World referring to all these cities and countries that haven't been mapped yet.

Satellite imagery and digitized old maps

Part of the new data will be collected by Fishman and the three PhD students and postdoc he can hire thanks to the grant. Partners around the world, mainly in the Global South, will also contribute, creating a network of researchers.

To find out which materials are used in buildings and cities, and how many of them, Fishman and his team examine a combination of satellite imagery, crowd-sourced open street data, and even digitized old maps. In some cases, on-site research is required: 'There is only so much you can derive from maps and models. Sometimes you just need to see it.'

Better response when disaster strikes

Fishman marvels at the opportunities a more comprehensive dataset of the world's buildings can provide. He imagines a future with sustainable and circular buildings, where cities in emerging countries take the lead. 'Mistakes that have been made in Western countries could be avoided.'

But Fishman also thinks of moments when disaster strikes. 'Imagine we had good models during the recent earthquake in Turkey and Syria,' he says, 'We would have been able to see exactly which construction materials were lost and what was needed for the recovery. The same is true for Ukraine. With good data, we would be able to better assess the physical impacts of war.'

Text: Samuel Hanegreefs

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