Building with salvaged materials is trendy in the world of high-end single-family home construction, but most large-scale, urban projects — upzoned multi-family housing, high-rises, infrastructure — have yet to embrace reuse. But what if they did? What if urban planners and contractors could begin to see their cities as sites of potential “urban mining,” full of concrete, steel and glass ready for re-appropriation, rather than blank canvases requiring ever more raw materials?
“From 1900 to 2010, the amount of materials accumulated in buildings and infrastructure across the world increased 23-fold,” the two recently wrote in The Conversation. “We are depleting our resources at unprecedented rates. Instead of extracting dwindling raw materials from nature at ever-increasing cost, the time has come to start re-using materials from buildings and infrastructure in our cities.”
The pair has been working on identifying the resources that cities could potentially “mine” from inside their borders, focusing on Melbourne, Australia. They’ve proposed a model that cities can use to determine what resources are available for re-use. They write:
For the 13,075 buildings [modeled], we ended up with more than 500 million data points. We needed to come up with effective data visualization to inform decision-makers about how we can mine cities.
The most important result we found is depicted in a map showing the quantities of each material within each building. We are able to do that for any given year or period. This enables us to track which materials are expected to be replaced in what quantities and in what buildings.
Using the concept of the “age pyramid” from population studies, they were able to determine “which materials stay in the stock and for how long.” Unfortunately, the pair’s research also highlights some of the main obstacles toward the circular economy they envision. For one thing, buildings aren’t designed for disassembly. Even if materials are salvageable, they’re often damaged beyond repair during the demolition process.
They suggest, among other things, rethinking “how construction materials and systems are designed and for what purpose.” They write:
Instead of buying carpet for an office, a company could pay for the service floor area covered by carpet. This would shift ownership of the carpet to the supplier. In turn, that would create an incentive to produce durable, high-quality materials that could be re-used and recycled, instead of programmed obsolescence.
Rachel Dovey is an award-winning freelance writer and former USC Annenberg fellow living at the northern tip of California’s Bay Area. She writes about infrastructure, water and climate change and has been published by Bust, Wired, Paste, SF Weekly, the East Bay Express and the North Bay Bohemian.