5 ways to build circular cities for a sustainable future

Designers, engineers, and inventors have long looked to nature for inspiration, creating innovations as diverse as airplanes (inspired by birds), ventilation systems (termites), bullet trains (kingfishers), and Velcro (burrs). Now, the natural world is serving as a model for circular cities—sustainable urban systems that minimize waste and pollution by reducing, recycling, and reusing.

Nature is the perfect model for such an endeavor. After all, it wastes nothing: Dead plants and animals decompose into nutrients that are consumed by the Earth and then used to create a new cycle of living things.

Circular cities are cities that are moving from a linear economy to a circular economy. In a linear economy, raw materials are used to build goods and products that are then discarded without thought for their potential reuse. According to the Ellen MacArthur Foundation, in this take-make-waste system, cities are major offenders, producing 50% of global waste and 60%–80% of greenhouse-gas emissions. But there’s an opportunity to create change.

A circular economy is a system of designing, making, and using things that respects the limited resources of the planet. In a circular economy, products and processes are redesigned to eliminate waste and pollution, products and materials are reused, and natural resources are renewed.

Here are 5 ways to move toward a circular economy:

Green infrastructure—a planned network of natural and seminatural areas—is one method that cities can use to address waste management, stormwater management, heat stress, air quality, and biodiversity. For example, green roofs and facades can reduce waste in the construction industry by extending the life of exterior surfaces. Rooftop architecture, such as gardens, can provide a protective layer against sunlight and high temperatures, doubling the lifespan of traditional flat roofs. Likewise, green facades lower the maintenance requirements of conventional facades. The insulating effects of green roofs and facades also help regulate indoor temperatures year-round, saving energy. Another benefit of greened surfaces? They’re a heck of a lot nicer to look at than concrete.

Moving from a linear to a circular economy is no small task. It’s challenging and time-consuming, involving major changes to infrastructure, business models, logistics, and social behavior. To get started, cities must create circular systems that separate economic growth from new material use, supporting renewable resources and keeping them in the loops as long as possible. Integrating circularity into municipal policies also means getting all public- and private-sector stakeholders on board. By supporting the principles of circular economies, cities may also uncover another benefit: They might help stimulate local entrepreneurship and innovation.

When buildings are renovated or demolished, where does all that glass, steel, wood, and concrete go? Often, it goes to the dump, the same place where the old or out-of-style furnishings and fixtures end up. Even when new commercial buildings are constructed, leftover materials, including those that are unopened and in pristine condition, are often tossed. These practices are a huge waste of money and resources, but they’re changing as the circular economy starts to gain traction in the real-estate industry, where it promises to have a major impact on not only the environment but also on companies’ bottom line.

Seven cities across the globe are leading the way in the effort to move to a circular economy. San Francisco, a long-time global leader in recycling, reuses 80% of all waste and aims to reach zero waste by next year. In Copenhagen, Denmark, 62% of residents bicycle to work every day, where they enjoy Europe’s shortest working hours and can join in on free sports activities. (Not surprisingly, the denizens of this city are among the healthiest and happiest in the world.) And Whanganui, New Zealand, boasts the world’s first body of water to be granted the legal rights of a person. The Whanganui River, which the indigenous Maori consider an ancestor, is overseen by two legally appointed environmental guardians; personhood status also helps protect the native traditions of the Maori.

With global population forecasted to reach 9.8 billion by 2050—and cities housing nearly 70% of that number—a host of ecological, social, and economic challenges loom large on the horizon. The architectural and urban-planning firm Skidmore, Owings & Merrill (SOM) has designed a city of the future that creatively addresses these issues. In SOM’s vision, cities are a collection of densely developed urban hubs that are linked by high-speed rail. Self-contained neighborhoods make nearly all daily services just a short walk away. City centers are located inland, far from rising bodies of water, and feature green, modular buildings that can be built with greater speed and less waste. They also boast flexible interiors that can adapt to changing business or residential needs and offer shared spaces that support community and well-being.

This article has been updated. It originally published in August 2019.