urban metabolism

Urban Metabolism of African Cities

by Paul Currie
first published on makingofcities.org

I wander through cities and hear them humming around me. They are creatures, machines, fixtures, breathers, parts and pieces, relationships, conduits, conductors, caretakers and crushers. Each city has its own sounds and its own energies that draw my attention and set the rhythm of my feet. The unique vibes in different cities is unquestionable, but cities do follow very similar processes (see Radiolab Podcast). Each city has systems for moving people around, for bringing food from afar, for delivering electricity to our light bulbs, water to our mouths, and data to our phones. These actions or processes can be understood as flows, simple or complex, interwoven, and present in the thousands. These flows of materials, energy, people and information form the metabolism of the city and are responsible for its existence. Unfortunately we do not have enough information about how these flows are conducted within cities, particularly in the global south, which means decisions about service delivery or sustainability are often made without data to prove their efficacy.

Studying urban metabolism allows us to visualise and explain the complexity of socio-technical and socio-ecological processes by which flows of materials, energy, people and information enter and shape the city, service the needs of its people, and impact the surrounding environment. More simply, it shows how the city functions, what type and quantity of resources it uses, and how heavily the city impacts its environment. To aid exploration of urban metabolism, some conceptualise cities as organisms, while others as ecosystems. I prefer the suggestion that most contemporary cities behave as organisms, while the ideal city behaves as an ecosystem: An organism ingests food and water to power its body, to keep it living and thriving. Its wastes are then excreted, out of sight, out of mind. This is a typical modern city: resources come in, are used in processes of economic production (and hopefully human welfare), before the wastes are dumped in the surrounding environment. Cities tend to be located on key resources – most are on water and on fertile agricultural land. Of course there are those which defy a bioregional attitude and are placed on desert or on mineral wealth (Dubai, Las Vegas, Johannesburg). The wastes of cities have huge consequences for a city’s hinterland, undermining natural ecosystems or poisoning people downstream. The global trade apparatus is so established that nations can even export their wastes to poorer places. Thus, a simple goal of urban metabolism analysis could be to make more efficient use of the fresh materials coming into the city, and to properly reuse or recycle waste flows. This is how the ecosystem conception is useful. Ecosystems are defined by relationships between organisms and abiotic systems. In the same way that an ecosystem makes use of detritivores to break down biological wastes into reusable nutrients, so too could the perfect city use our wastes to power its systems. Stockholm powers busses based on biogas from its sewage system. Toronto’s wastewater system contains enough chemical energy to power itself (Bristow & Kennedy 2013). A cyclical metabolism is not only possible, but necessary for growing sustainable cities with low social and environmental impact.

It should be acknowledged that sustainability has multiple approaches. The mainstream sustainability discourse preaches resource efficiency. This is fine for developed spaces of the global north, where overconsumption is the daily routine. However, for countries in the global south, most people do not have access the basic resources they need, so the priority for these spaces is resource equity. The lack of formalised infrastructure in many of these spaces provides an opportunity to create infrastructure systems that are equitable as well as efficient.

Shaping infrastructures requires assessing how flows are conducted in these cities. Resource flows can be formally coordinated and regulated by city planners or government, or follow informal patterns where government is unable or unwilling to provide resources. This can be visualised as the distinction between networked water pipes and decentralized water tankers, bottles, boreholes or sachet water provision, or by comparing supermarket tomatoes to those bought on the streetside. Both systems effectively get water or tomatoes to people, yet informal systems are typically shunned as they do not fit the desired northern (America, Europe, Asian Tigers) image of a modern city. This is problematic as informal systems predominate in cities of the global south and in Africa. Tapping into the innovation and adaptability of informal systems can be useful for city practitioners in providing services or addressing necessary city functions. The successes of waste picking systems in Brazil, India, and Egypt are easy examples.

African cities predominantly function on informal systems as much of the networked infrastructure remains within the boundaries of original colonial settlements. Informality pervades public transport systems, water and food provision, energy generation and waste removal. Analysing these flows is difficult as they are hard to track and quantify. However, finding ways to do so is an important step for empowering city planners with more knowledge about the functions of their cities.

African cities may share attributes such as informal economies, slum dwelling, high youth unemployment, migratory citizens, precarious infrastructure systems (see the Nigerian fuel strike), resource and wealth inequality (see the Dumsor Report), and industrialisation within planetary boundaries. However, it is impractical to make singular recommendations about African urbanism when city practitioners in Arusha will be dealing with very different realities from those in Abidjan. More local urban metabolism studies would be invaluable.

Global urbanisation trends suggest that African cities will house one billion new urbanites by 2050. To aid studies of sustainability or urban metabolism in African cities, it is vital to make a shift from discussing African urbanism as a collective event. The oft-quoted statistic that Africa is 40% urban (the world purportedly passed 50% urban in 2008) overlooks the fact that 17 of 54 African nations are over 50% urban, 9 of which are over 60% urban, and 4 of which are over 70% urban: the African urban future is here. Meeting it with new visions for the sounds and energies of these cities will make all the difference.

Interesting Reads:

  • Bettencourt, L.M., Lobo, J., Helbing, D., Kuhnert, C. & West, G.B. 2007. Growth, innovation, scaling, and the pace of life in cities. PNAS. 104(17):7301–7306.
  • Bristow, D.N. & Kennedy, C.A. 2013. Urban Metabolism and the Energy Stored in Cities: Implications for Resilience. Journal of Industrial Ecology. 17(5):656–667.
  • Kennedy, C., Cuddihy, J. & Engel-Yan, J. 2007. The Changing Metabolism of Cities. Journal of Industrial Ecology. 11(2):43–59.
  • Krausmann, F., Fischer-Kowalski, M., Schandl, H. & Eisenmenger, N. 2008. The Global Sociometabolic Transition. Journal of Industrial Ecology. 12(5/6):637–656.
  • Pieterse, E. 2014. Filling the void: an agenda for tackling African urbanisation. In Africa’s Urban Revolution. S. Parnell & E. Pieterse, Eds. London: Zed Books. 200–220.
  • Turok, I. 2014. Linking urbanisation and development in Africa’s economic revival. In Africa’s Urban Revolution. S. Parnell & E. Pieterse, Eds. London: Zed Books. 60–81.