Urban Metabolism is a framework for modeling complex urban systems’ flows – water, energy, food, people, et cetera – as if the city were an ecosystem. It can be used to analyze how urban areas function with regard to resource use and the underlying infrastructures, and the relationship between human activities and the (natural) environment. What is more, it can be used to shape the urban environment in a more sustainable way.
The metaphor of a city, or living environment, as a living organism with a collective urban metabolism can be traced back for more than 150 years. Though metabolism was at first used to describe living organisms, pioneering ecologist Arthur Tansley expanded the term in 1935 to encompass the material and energetic streams from the inorganic construction of settlements, and introduced the ‘Urban Metabolism’.
More recently, the concept of urban metabolism has been used as an analytical tool to understand energetic and material exchanges between cities and the rest of the world. Christopher Kennedy recently updated the definition of urban metabolism to ‘the sum total of the technical and socio-economical processes that occur in cities, resulting in growth, production of energy, and elimination of waste’. It has strong relations to other concepts that build upon mimicking nature, like Biomimicry by Janine Benyus, and Cradle to Cradle by William McDonough and Michael Braungart.
Originally, urban metabolism approaches aimed at quantifying inputs, outputs and storage – or: flows and stocks – of the urban system. More recently, recycling of resources and interconnection of flows within the urban environment are incorporated, aiming for a more circular urban metabolism. Here again, processes in nature where cycles are closed and waste from one process is input for another, are models for the urban situation.
To be able to apply this concept to urban design and planning, one has to understand the different flows and the different scales of the city and its hinterland as well as the corresponding infrastructures. The relevant types of physical infrastructure (present in the Netherlands) which are considered in regard to the concept of Urban Metabolism, are as follows:
- Water supply; water extraction and purification, drinking water supply network;
- Wastewater treatment; sewer, wastewater treatment plants, recovery installations;
- Solid waste management; solid waste collection, separation facilities, transportation infrastructure, landfills, incineration facilities;
- Energy supply; electricity generators, electricity grid, heat network, pipelines for liquid or gaseous energy carriers;
- Food supply; farms, nutrient supply, storage facilities;
- Transportation; roads, bicycle infrastructure, pedestrian infrastructure, canals, public transportation.
The morphology of infrastructure is directly linked to the quality of urban metabolism, and the design and engineering of these infrastructures, imbedding them into the urban environment, is therefore of great importance.
For a more elaborated definition of Urban Metabolism, please read our position paper The Concept of Urban Metabolism by prof.dr.ir. Arjan van Timmeren.