The cities of today are built with concrete and steel – but some Cambridge researchers think that the cities of the future need to go back to nature if they are to support an ever-expanding population, while keeping carbon emissions under control.
Between them, concrete and steel are responsible for as much as a tenth of worldwide carbon emissions. Before they ever reach a construction site, both steel and concrete must be processed at very high temperatures – which takes a lot of energy. And yet, our cities are completely dependent on these two unsustainable materials.
“I fly back and forth a lot between the UK and the US, and I’d been harbouring a lot of guilt about the effect that had on my carbon footprint – I’d always assumed, as many of us do, that air travel is a huge contributor to carbon emissions,” says bioengineer Dr Michelle Oyen of Cambridge’s Department of Engineering. “But the truth is, while the emissions caused by air travel are significant, far more are caused by the production of concrete and steel, which of course is what most cities are built from.”
So what does that mean for cities of the future, as more and more of us live in urban areas? How can we continue to build while reducing carbon emissions?
Whereas some researchers are investigating ways of producing steel and concrete in more energy-efficient ways, or finding ways of using less, Oyen would rather turn the tables completely, and create new building materials that are strong, sustainable and take their inspiration from nature.
“What we’re trying to do is to rethink the way that we make things,” says Oyen. “Engineers tend to throw energy at problems, whereas nature throws information at problems – they fundamentally do things differently.”
Oyen works in the field of biomimetics – literally ‘copying life’. In her lab, with funding support from the US Army Corps of Engineers, she constructs small samples of artificial bone and eggshell, which could be used as medical implants, or even be scaled up and used as low-carbon building materials.
Like the real things, artificial bone and eggshell are composites of proteins and minerals. In bone, the proportions of protein and mineral are roughly equal – the mineral gives bone stiffness and hardness, while the protein gives it toughness or resistance to fracture. While bones can break, it is relatively rare, and they have the benefit of being self-healing – another feature that engineers are trying to bring to biomimetic materials. […]