Posted April 28th 2014 at 10:21 am by
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City Science tackles Energy: Urban Metabolism

Kurokawa’s Toshiba-IHI Pavilion, Osaka Expo 1970

In the previous installment of CoLab Radio’s City Science series, we explored a City Science approach to spatial planning and showcased standard and cutting edge modeling practices applicable to urban design and development. This week’s post focuses on City Science approaches to energy and sustainability. 

The essence of life is process, according to General Systems Theory. In turn, processes require energy to function. Energy is harnessed and manipulated in systems at a variety of scales ranging from cells to ecosystems, or from batteries to entire industries. Since the early 1960s, architects and urbanists with an eye towards sustainability have concerned themselves in particular with processes of metabolism in living organisms as inspiration for how we think about energy and materials flow through buildings and cities.

Can we truly liken a city to a living organism? What parts of the metabolic model are actually applicable to urban design? I would argue that mimicking the form of living systems is not enough. We must focus our attention on the principles of metabolic processes in living systems. This requires an understanding of how metabolism actually works in nature, and acknowledging that biological energy processing is not always efficient. We can draw inspiration from these systems as long as we keep in mind where cities are different.

Metabolism is the process by which energy is consumed, processed and recycled in living organisms. Here’s a quick primer on how energy processing works in cells, perhaps the best understood and most elegant metabolism process of all.

Cell metabolism is in fact two processes that are codependent: catabolism and anabolism. Catabolism breaks down organic matter and harvests energy via cellular respiration. Anabolism uses that energy to construct parts of cells such as proteins or nucleic acids. Energy released from catabolic chemical reactions that are energetically favorable (that is, they are able to occur spontaneously), literally activate transporter molecules that carry this energy to other processes in the cell that need it. Biologists sometimes liken energy to a form of currency between processes in the cell. Notably, the basic unit of this currency is Adenosine Triphosphate (ATP) and the enzyme that generates it, ATP-Synthase, is a truly remarkable machine (see video!).

Cell Metabolism Chart (Wikimedia)

The early architectural approach to Urban Metabolism focused on physical forms that might arise in futuristic “living” cities. These forms showcased what shape a “metabolic city” would take, but failed to develop a framework or plan for how cities could modify their consumption habits at the time. In part, due to critique of this movement, sustainable urban design strategies today try to link form and function together by predicting the effects of design-decisions on the overall behavior of a site, block or neighborhood. These models are distinctly different from their predecessors because they focus on processes that link building form to a holistic projection of city function.

Here’s a bit of history: enter Patrick Geddes, a 19th century biologist who first attempted to liken social processes to metabolic ones in living systems. Geddes considered how sources of energy were transformed through social and industrial processes. Marx and Engels later expanded the metaphor to the development of civilization, hypothesizing that the harvesting of resources from the earth by human labor is itself a metabolic process that generates and sustains civilization. Urban metabolism ideology reached its zenith when it entered the architectural lexicon in 1960. Architect Kenzo Tange unveiled his metabolism manifesto at the Tokyo World Design Conference. His conception of urban metabolism, in which cities were viewed as ever-evolving processes, manifested itself in physical form. These structures were built around a spine-like infrastructure with prefabricated modular components and were intended to have a limited “life-span,” necessitating their replacement. Subsequent spin-off’s such as Kisho Kurokawa’s 1961 “Helix City,” dominated the urban metabolism conversation up until the 1980s.


Kisho Kurokawa’s Helix City plan and model (1961).

Addressing metabolism through form alone proved to be a limited scope for the overall conversation on energy sustainability arriving in the late 1980s. Shortly after the construction of Capsule Tower, Christopher Alexander in “The City is Not a Tree” reacted to Tange’s work by highlighting the importance of relationships between parameters of the city from which form arises.

“For example, in Berkeley at the corner of Hearst and Euclid, there is a drugstore, and outside the drugstore a traffic light. In the entrance to the drugstore there is a newsrack where the day’s papers are displayed. When the light is red, people who are waiting to cross the street stand idly by the light; and since they have nothing to do, they look at the papers displayed on the newsrack which they can see from where they stand. Some of them just read the headlines, others actually buy a paper while they wait. This effect makes the newsrack and the traffic light interactive…they form a system – they all work together.”

Such relationships, argues Alexander, is where we should focus design intervention.

Urban metabolism as practiced today acknowledges these relationships, and attempts to link form to energy consumption. Energy Proforma, is one such example. This online design tool estimates energy usage for a site, block or neighborhood based on a suite of urban design choices. Consumption levels vary as a consequence of density, position, floor-area-ratio (FAR), public transportation access, or materials. Carbon emissions are similarly assessed, providing a better picture of how design decisions based on form affect energy consumption and its byproducts.

Once again, the success of these tools is contingent on the availability of information. According to the MIT Urban Metabolism Review, “metabolism data have been established for only a few cities worldwide and there are issues of interpretation due to lack of common conventions (8).” Eventually, we need to develop a consistent language and standards by which to define urban metabolic processes, as well as a robust data set to support evidenced-based design and planning. Whether or not Urban Metabolism already is, or should aspire to metabolic processes in natural systems remains a question. But the importance of urban energy consumption cannot be understated with the release of the IPCC’s most recent climate change report.


Other sources:

 The Metabolism of Cities by Abel Wolman

Metabolism: The City of the Future (Tokyo Exhibition)


Emily Royall is a Masters in City Planning candidate in City Design and Development at the Department of Urban Studies and Planning at MIT.

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