CIRCULAR CITIES
“We need to understand cities as a massive leverage point. They only occupy around three percent of the surface area of the planet, but they consume 75 percent of the resources, and they´re responsible for 60 to 80 percent of greenhouse gas emissions. If you can redesign cities from the current resource drains, you can create entirely new forms of prosperity for the people living in those cities.”
― Eva Gladek, Founder and CEO of Metabolic
Introduction
Six years ago, Christopher Brosse participated as an observer in a consultancy session for a Colombian company on their journey towards making its Circular Economy strategy. As the company's operations were presented, a phrase caught his attention – "the circular metabolism". It was the first time that he heard about that concept. The concept elucidates how a company, much like a living organism, has a metabolic processes. Materials flow in and undergo various transformations. A company, a city, or a country is in reality not a static entity, but a living organism that receives raw materials and releases waste, products or by-products, emissions, and chemicals to the planet, pretty much like how nutrients move through a human metabolism!
A city isn't merely a collection of buildings and infrastructure, but a dynamic, interconnected system with its metabolic rhythm. An unhealthy city will produce tons of chemicals and waste. A circular and healthy city can have the power to optimize the use of resources within a city, ensuring efficient energy production, sustainable growth, and effective waste elimination to promote the well-being of the urban environment and its inhabitants.
Abel Wolman introduced the concept of urban metabolism in 1965 to study how energy and materials move within cities, focusing on a hypothetical city of one million people. Urban metabolism, as defined by Wolman, includes all materials necessary to sustain a city's inhabitants in their homes, workplaces, and leisure time. Today, cities have increasingly used this approach to analyze resource flows and improve efficiency, sustainability, and resilience.
Recently, researchers from the University of Toronto redefined urban metabolism as the sum of the city´s technical and socio-economic processes, considering environmental, social, financial, and information flows. This expanded definition incorporates spatial and temporal distribution, including infrastructure outside the city.
The main challenges for cities in the 21st century
Cities worldwide grapple with severe ecological challenges like air pollution, water pollution, waste management, deforestation and loss of green spaces, climate change resilience, overconsumption of resources, carbon-based energy, land use change, noise pollution, and social inequalities. These challenges pose a grave threat to public and environmental health. According to the World Health Organization (WHO), approximately 99% of the global population resides in areas where air quality exceeds the guideline limits for particulate matter (PM2.5), leading to around 4.2 million premature deaths annually. This alarming statistic underscores the urgent need for comprehensive measures to mitigate the impact of urban air pollution on respiratory and cardiovascular health.
Another critical ecological concern in urban environments is the increasing waste generation. Cities generate an estimated 7 to 10 billion tonnes of urban waste yearly, and 3 billion people worldwide lack access to controlled waste disposal facilities. This has far-reaching consequences, from endangering marine life to contaminating drinking water sources and adversely affecting the delicate balance of ecosystems.
However, if we are talking about the future of cities, we need to address the African region. Sub-Saharan Africa is undergoing the swiftest global urbanization, evolving into several "megalopolis": large and densely concentrated metropolitan centers. Among the 20 largest cities of the future, 13 are projected to be in Africa, with none in the "developed" world. This rapid urbanization is already accompanied by challenges such as polluting infrastructure, population health issues, social insecurity, economic inequalities, and the erosion of local cultures. Today, a megalopolis is an example of everything but a sustainable city.
Nevertheless, the better we comprehend how to advance toward circular cities, the greater the opportunities for newcomers to adopt sustainable and circular policies, infrastructure, and business models.
WE TAKE: Cities consume almost half the resources extracted globally. According to some scenarios, most of the world's largest cities in 2100 will be in Africa. Today, 56% of the world’s population (4.4 billion inhabitants) live in cities. This trend is expected to continue, with the urban population doubling its current size by 2050. Nearly 7 of 10 people will live in cities, and 4 out of 10 will live in Africa.
WE MAKE: Given that over 80% of the world's GDP is produced in urban areas, cities can influence the broader landscape of the linear economy by determining the methods and processes employed in creating products and services.
WE DISPOSE: According to the United Nations Environmental Program (UNEP), cities produce up to 10 billion tonnes of waste yearly and an estimated 70% of all global greenhouse gas emissions.
What is a circular city?
According to the Circular Cities Declaration: “A circular city promotes the transition from a linear to a circular economy in an integrated way across all its functions in collaboration with citizens, businesses and the research community.”
In practical terms, a circular city cultivates innovative business models and economic behaviors that deliberately decouple resource use from economic activities. The critical strategy lies in prolonging the value and utility of products, components, materials, and nutrients for as long as possible: it involves a commitment to closing material loops and creating ecosystems where resources are continually reused and recycled, thereby minimizing the detrimental impacts of resource use and waste generation. However, a circular city understands that key value chains exist, such as electronics and ICT, batteries and vehicles, packaging, plastics, textiles, construction and buildings, and food. They also recognize that, on a larger scale, cities are the primary consumers of energy and materials. Finally, they understand that they must successfully integrate a systemic approach to shift from the linear to the circular.
The city as a living organism.
Throughout this chapter, the overarching goal is to enhance various aspects of urban life. A circular city aims to improve human well-being by ensuring sustainable resource practices and reducing the environmental footprint associated with traditional linear economies. From the outset, it is crucial to highlight that every facet of city metabolism, encompassing materials, food, energy, sustainable finances, water, and social capital, plays a role in advancing the overarching goal of circular cities. Each city operates as a living entity, and every example in this chapter presents a different approach to a circular metabolism for your inspiration.
If you're enthusiastic about designing improved products and services to promote circularity in your city or wish to understand the intricacies of achieving a Circular City. Then, this chapter is tailored for you. We present many 4Revs cases which rethink the way cities use and make energy, transportation, products, housing, interactions, and policy. Furthermore, this chapter aims to answer the following questions:
What is the promise of smart cities? Could smart cities be circular?
What are the key socio-environmental urban challenges?
What are the needs of a circular city?
Is there a roadmap to create circular cities?
As you conclude this chapter on circular cities, we sincerely hope it ignites a spark within you to advocate for a more circular urban environment through your professional endeavors. May the insights gained here propel you to contribute actively to realizing a sustainable and circular city from your workplace.
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