Rethinking Cities: An Urban Metabolism Approach

urban metabolism 3

Introduction

In contemporary times, when more than half of the world resides in urban, it has become indispensable to contemplate cities’ sustainability. This idea of sustainable cities brings up the importance of ecological sustainability from the periphery to the core of the discourse. Historically, nature is imagined as something outside the city. This conventional imagination has its root in ‘nature-culture dualism’. In this approach, culture and nature are conceptualized separately; the former is equated to the human artefact while the latter is considered an external environment.

This dualism has been produced and reproduced over time through academic literature2. In this context, the conceptualization of urbanization as something against nature, or exists far away from cities and cases if presented in the city, needs to be tamed. This approach to cities manifests in every aspect of city life from planning to infrastructure. The birth of modern planning institutions is the outcome of this approach, striving to deploy measures for cities’ natural ordering. The provisions of parks, embankments of rivers and lakes, homogenous sewerage, or piped water systems are examples of such imagination (see Figure:1 and Figure: 2 which show how nature is organized in cities). This dualism has a debilitating effect on the comprehension of ecological issues. Cities worldwide, face the repercussions of natural disasters and hazards such as floods, droughts, water crisis, urban heat land, social inequity, and ecological instability reinforced by anthropogenic activities.

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Figure 1: Sankey Tank, Bengaluru, Source: Prathistha Kohli
urban metabolism
Figure 2: Kamla Nehru Park, Pune, Source: Aarya Pathak

“There is nothing un-natural about New York City.”                           

~David Harvey (1993)

Many scholars tried to disrupt this dualism and established the fact of how humans are an integrated part of nature. In terms of urbanisation, cities are created by humans and humans are creatures of nature; thus, discriminating between phenomena of nature and the city does not make sense at all2. In this backdrop, the of ‘urban metabolism’ helps us to re-visit cities as a part of nature.

In this approach, the city is considered as an organism which is living, thriving and excreting. In a nutshell, there is an analogy between an organism’s metabolic process with the production and consumption patterns of the city. One may argue that cities are more complex than an organism and consist of a multitude of organisms; hence, it is more appropriate to call the city as an ecosystem. The concept of urban metabolism was first conceived by Wolman (1965) for studying American cities3. There are many ways to define urban metabolism, one of the widely accepted definition was given by Kennedy et al. (2011) which defined urban metabolism as “the sum total of the technical and socio-economic processes that occur in cities, resulting in growth, production of energy, and elimination of waste”. Urban metabolism can be characterised by social justice, ecological sustainability, and economic efficiency of different city activities.

Furthermore, urban metabolism as a systematic tool integrates into cities’ biophysical metabolism activities such as energy, material and water with social metabolism characterised by conflicts across caste, class, and geographic-demographic axes4. It also provides a basis to understand how social relations generate or re-generate the bio-physical metabolic flows or vice-versa. Figure 3 shows the urban metabolism framework of a city which represents inflow, processes and outflow of material and energy in a city.

urban metabolism framework
Figure 3: Urban Metabolism Framework, Source: Author

In this piece, I focus on two critical aspects, i.e., ‘system and process’ of urban metabolism. By system, I mean to conceive the city as part of the whole complex system rather than seeing it as an independent entity. This implies that city as a part of the system can be separated, but it loses its functionality. In short, a city cannot stand alone. Metabolic flows share a two-way relationship with the circulatory system.

Hence, to underscore the importance of interconnections and interdependence of the city on its immediate surroundings and even beyond, it becomes crucial to understand the city’s niche or context (geographical, climatic, ecological, social and economic). For instance, as an urban agglomeration, Delhi has an interdependence with its surroundings for water, food, energy and even for people. Apart from groundwater, Delhi gets its water from the Ganga Canal (~150 Km), the western Yamuna canal (~88 Km), the Bhakra canal (~164 Km) and the Yamuna and the wastewater and effluents get disposed in the Yamuna. Furthermore, there is a constant flow and circulation of people within the city and the surroundings who interact with and influence its bio-physical metabolism. Hence, there are intertwined metabolic flows and circulations within the city located in a broader system.

While talking of processes, every system has multiple functions that operate to ensure the system’s functionality. In urban metabolism, the process can be defined as the sequences of interrelated tasks, that occur to operate a system by transforming input into some output. In the process, the quality of outflow is transformed and become considerably different from inflow material. Keeping the ‘processes’ at one of the foci allows us to keep the political, economic, and social procedures and institutes involved in decision-making with the city’s bio-physical metabolism. Urban metabolism enables us to open the black-box of processes and embrace the complexity of the system.

A city’s metabolism can be understood through the interaction of various bio-physical processes such as hydrological flow, energy flow, material flow, or people flow. In this work, I have attempted to decipher the city’s hydrological flow through the lens of urban metabolism. Water is tightly coupled with the social-ecological system and provides a good case to understand the mechanism of urban metabolism. The urban water has been studied with the lens of urban metabolism that offers the critical tool for revisiting ‘the politics of distribution and production of water’ in urban centres3,5. In other words, how the flows of water and the flows of power and their inter-linkages for turning into monetary values determines the quality and quantity of urban water3.

Understanding Water through the lens of Urban Metabolism

I have used water to understand the urban metabolism of a city in the general and specific case of Bengaluru. Studying water with the lens of urban metabolism allows us to see the city’s hydrology in the broader system. It asks ‘questions’ about the processes involved in the hydrological flow of the city. A water mass balance is the most basic description of water metabolism. It details how a city draws upon many different sources to meet its water needs and keeps track of waste flows.

The Figure 4 represents the hydrological flow and circulation of a city in which the inflow of water into the city through natural (river, rain, or groundwater) or anthropogenic ways such as bringing water through canals and pipelines from distant sources. Within the city, the surface water or the fetched water interact with the groundwater in multiple ways. Besides this, the water system also interacts with the local environment (city’s ecology, built environment and infrastructure), energy flow and inhabitants of the city.

Moreover, the urban metabolism framework is well-suited to investigate the nexus between social equity, biophysical sustainability and economic efficiency. The processes involved in production, distribution, exchange, use and disposal of water can be unveiled with the framework’s help. The ‘bio-physical sustainability’ of exiting water systems, i.e., water source, infrastructure, institutes, and other involved systems at different scale, can be examined using the urban metabolism approach.

Furthermore, ‘social equity’ can also be answered which may include: what are the different uses of water (allocation of water for various activities, i.e., industrial, domestics or other services)? Who is getting how much? Who is included, and who is excluded and why? Who has a say over what source of water? Last but not least, it also permits us to ponder on ‘efficiency’, for say, how is water getting allocated? What are the infrastructural arrangements made? How is the system operating? Taking one step ahead, the comprehensive study of the hydrological system may qualify us to diagnose the system’s issues. These diagnoses could have spatial characteristics, infrastructural problems, or governance at
varied scale.

Water through the lens of urban metabolism
Figure 4: Water through the lens of urban metabolism, Source: Author

Water Metabolism: A case study of Bengaluru


Bengaluru or Bangalore is one of the fastest growing cities and known for IT sector boom in recent years. In four decades, Bangalore has grown from 1.65 million people in 1971 to 8.5 million people in 2011 while the built-up area has increased from 20 percent in 1971 to about 80 percent in 2011.

In the last two decades, much of this growth has happened in the peripheries of Bengaluru (figure: 5). In addition, the physical jurisdiction of the city has expanded by nearly 40 % – the Bruhat Bengaluru Mahanagara Palike (BBMP) or the Greater Bangalore City Corporation was formed in 2007. The water metabolism of Bengaluru is defined in the next section.

Social Hydrology of Bengaluru

In contrasting many large cities, Bengaluru does not have any seasonal or perennial water. However, it has man-made lakes or the Kalyani system that used to be the primary water source until 1896. In 1896, the city got its first piped water supply from Hesaraghatta lake, built across the Arkavathi. The major expansion occurred when the Chamaraja Sagar reservoir was constructed downstream of Hesaraghatta in 1933, nearly 25 km from the Bengaluru. The Bangalore Water Supply and Sewerage Board (BWSSB), an autonomous body under the state government, has managed the piped water supply since 1964. The BWSSB is responsible for providing adequate water supply and sewage disposal for Bangalore. It has also brought water from Cauvery river (100 km away from the city) since 1974 in phases5. Figure 6 and 7 represent the water timeline and systematic representation of external water sources to the city respectively.

Figure 6: The water timeline of Bengaluru, Source: BWSSB[1]
Figure 7: The systematic representation of external water source to Bengaluru5

Hence, the total inflow of water to the city include around 1700 MLD (million litre per day) from rainfall and nearly 1400 MLD from the external water supply. Currently, the BWSSB is serving 9.5 million people through the pipeline length of almost 8,700 km by covering 800 sq. km area. The distribution network of 8,700 km requires a total of 62 booster pumping station and 52 reservoirs in the city. Every day, close to 1450 Million litre water from Cauvery river is required to pump at the height of approx. 500 m. Besides the surface water sources, the BWSSB also supplies about 70 MLD of groundwater from over 7,000 borewells. The city’s water treatment capacity, at 810 MLD, is approximately on par with the current water supply.

Water Metabolism of Bengaluru
Figure 8: Water Metabolism of Bengaluru , Source: BUMP[2]

The total energy consumed is approximately 50 GWH/month which alone account for more than 300 crore rupees annually. In addition, there are private pumps, tanker (which bring water from the adjoining villages of the city) and other water sources that remained unaccounted. The city’s water treatment capacity, at 810 MLD, is approximately on par with current water supply.

Figure 9: Tap water and Groundwater dependency based on Census 2011, Source: Author
Figure 10: Water infrastructure map (pipeline) for Bengaluru, Source: BUMP

The water in the city is used by households, industries, and for other purposes. The quantity and quality of water used by the city’s inhabitants are determined by the social power dynamics; for instance, some slums have piped water supply. The flow and circulation of water within the city is governed at the sub-divisional level. In terms of outflow, the city’s sewerage system is adversely lacking due to infrastructural inability- there are only 14 sewerage treatment plants with the capacity of 720 MLD, covering 60 per cent area of the city. Only half of an installed sewage treatment capacity is utilised, whereas wastewater is generated at more than 1000 MLD. The result has been the conversion of lakes of the city into waste sinks and carriers and groundwater pollution. Furthermore, due to the lack of waste management facilities, a significant proportion of the city’s waste is ended in the water bodies, which further exacerbate the quality of lakes in the city. 

Importance of urban metabolism in understanding cities

In the urban metabolism framework, the city is a living entity whose survival and growth are contingent on a steady throughput of matter and energy into the city and the return flow of waste product. An urban metabolic framework’s central approach is to explicitly acknowledge that human and natural systems are tightly coupled in urban environments. The urban metabolism helps us to open our debates around the processes involved in an urban system. The importance of urban metabolism framework to understand the cities are given below: 

  • In the urban metabolism approach, the city is considered a part of an ecosystem; hence, its dependence on its surroundings for resources and impact enables us to think beyond the rural-urban binary. 
  • Urban Metabolism framework allows us to open the black-box of urban activities and focuses on the bio-physical process, which otherwise remains untouched. It also allows us to simplify the complexities of urban issues without simplification (without losing the complexity). Hence, understanding the urban system’s processes within a complex system may help resolve many ecological and social issues in urban centres. 
  • It allows us to understand how one metabolic activity, for say, an urban water system intersects with other activities such as energy or land use and how they affect each other. For example, besides, bio-physical causes of urban flooding in any city, there exists a whole range of causes which need to be fixed together, such as land use, i.e., how is the built environment, how are the water bodies maintained, what is the level of groundwater abstractions and many more? In short, urban metabolism enables us to understand a city with an integrated approach rather than a sectoral approach. 
  • The diagnosis of urban issues can be made by studying the patterns and processes of the urban system. The urban metabolism will help to pinpoint the problems in the system.
  • This approach can also empower us to ask the following questions: What is the aggregate resource ingesting (consumption) within an urban system? How is an urban system depending on its surrounding? What are the impacts (ecological, economic and social) of an urban system on its immediate surrounding and what are the distant consequences?
  • The metabolic framework may help uncover why certain policy solutions like privatisation of public utilities in the interest of economic efficiency may fail in meeting their objectives, especially in the case of water privatisation.
  • Through the social and biophysical metabolism, the social power relations (whether material or discursive, economic, political, and/or cultural) directly or indirectly control the metabolic flows and circulations within/ out of a city can be understood. It may help to understand who can access and how much or who is excluded or included, and how?

In conclusion, urban metabolism as a framework is useful to break the nature-city binary. It also pushes to rethink nature, a city, and how they are conceptually different from each other. The given case from Bengaluru helped us to understand how biophysical processes of the city were inevitably integrated with its surroundings and also with the other metabolic activities within the city, such as energy and waste. The current metabolic activities are majorly linear in nature, by deploying processes and applying the system approach, these activities can be transformed into a circular system. In a nutshell, the urban metabolism approach can be one of the pathways to attain sustainable cities.

References

  1. Bangalore Urban Metabolism Project Episode 1: Introduction – Bangalore Urban Metabolism Project (BUMP). Retrieved January 9, 2021, from http://bangalore.urbanmetabolism.asia/2017/12/09/bangalore-urban-metabolism-project-episode-1-introduction/
  2. Haila, Y. (2000). Beyond the Nature-Culture Dualism. Biology and Philosophy, 15(2), 155-175.
  3. Kaika, M., & Swyngedouw, E. (2006). In the Nature of Cities-Urban Political Ecology and The Politics of Urban Metabolism TLR-Turning livelihoods to rubbish? Politics of waste and urban poverty View project Mortgaged Lives: the biopolitics of debt and homeownership financialisation View proj. https://www.researchgate.net/publication/275035207
  4. Kennedy, C., Pincetl, S., & Bunje, P. (2011). The study of urban metabolism and its applications to urban planning and design. Environmental Pollution, 159(8–9), 1965–1973. https://doi.org/10.1016/j.envpol.2010.10.022
  5. Mehta, V. K., Goswami, R., Kemp-Benedict, E., Muddu, S., & Malghan, D. (2013). Social Ecology of Domestic Water Use in Bangalore.

(Ref Footnotes)

[1] Bangalore Water Supply and Sewerage Board. (2020). Retrieved January 10, 2021, from https://www.bwssb.gov.in/

[2] Bangalore Urban Metabolism Project (BUMP). (n.d.). Retrieved January 10, 2021, from http://bangalore.urbanmetabolism.asia/

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Ritika Rajput

Ritika is an Urban Fellow at Indian Institute for Human Settlement, Bengaluru. She loves to learn about small towns, water, sustainability, and climate change. She wants to explore the urbanization of small towns of India that remain under-studied in urban literature.

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