Urban metabolism

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Urban metabolism is a model to facilitate the description and analysis of the flows of the materials and energy within cities, such as undertaken in a material flow analysis of a city. It provides researchers with a metaphorical framework to study the interactions of natural and human systems in specific regions. [1] From the beginning, researchers have tweaked and altered the parameters of the urban metabolism model. C. Kennedy and fellow researchers have produced a clear definition in the 2007 paper The Changing Metabolism of Cities claiming that urban metabolism is "the sum total of the technical and socio-economic process that occur in cities, resulting in growth, production of energy and elimination of waste." [2] With the growing concern of climate change and atmospheric degradation, the use of the urban metabolism model has become a key element in determining and maintaining levels of sustainability and health in cities around the world. Urban metabolism provides a unified or holistic viewpoint to encompass all of the activities of a city in a single model.

Contents

History

With deep roots in sociology, Karl Marx and fellow researcher Friedrich Engels may have been the first to raise concerns around issues which we would now call urban metabolism. Marx and Engels concentrated on the social organization of the harvesting of the Earth's materials by "analysing the dynamic internal relationships between humans and nature." [1] Marx used the metaphor of metabolism to refer to the actual metabolic interactions that take place through humans' exertion of physical labour to cultivate the Earth for sustenance and shelter. [3] In short, Marx and Engels found that when humans exerted such physical labour they ultimately altered the biophysical processes as well. This acknowledgement of altering the biophysical landscape is the first stepping stone for the creation of urban metabolism within social geography. They also used metabolism to describe the material and energy exchange between nature and society in as a critique of industrialization (1883) which created an interdependent set of societal needs brought into play through the concrete organization of human labour. Marx advocated that urban metabolism becomes a power in itself (like capitalism), and will control society unless society is able to control it.

Later, in reaction against industrialization and coal use, Sir Patrick Geddes, a Scottish biologist, undertook an ecological critique of urbanization in 1885, making him the first scientist to attempt an empirical description of societal metabolism on a macroeconomic scale. [4] Through his experimental study of urbanization he established a physical budget for urban energy and material throughput by way of an input output table. [3]

"Geddes' table consisted of the sources of energy and materials transformed into products in three stages: (1) extraction of fuels and raw materials; (2) the manufacture and transport; and (3) exchange. The table also included intermediary products used for manufacture or transport of the final products; calculation of energy losses between each of the three stages; and the resultant final product; which was often surprisingly small, in material terms, compared with its overall material inputs." [4]

It wasn't until 1965 when Abel Wolman fully developed and used the term urban metabolism in his work, "The Metabolism of Cities" which he developed in response to deteriorating air and water qualities in American cities. [2] In this study Wolman developed a model which allowed him to determine the inflow and outflow rates of a hypothetical American City with a population of 1 million people. [5] The model allows the monitoring and documentation of natural resources used (mainly water) and the consequential creation and out-put of waste. [6] Wolman's study highlighted the fact that there are physical limitations to the natural resources we use on a day-to-day basis and with frequent use, the compilation of waste can and will create problems. It also helped focus researchers and professionals of their time to focus their attention on the system wide impacts of consumption of goods and sequential production of waste within the urban environment. [7]

Working off of Wolman's pioneering work in the 60s, environmentalist Herbert Girardet (1996) began to see and document his findings in the connection between urban metabolism and sustainable cities. [6] Girardet laid the foundation for the industrial ecology approach to urban metabolism in which it is seen as the "conversion of nature into society." [7] Aside from being a great advocate and populariser for urban metabolism, Girardet significantly coined and drew the difference between a 'circular' and 'linear' metabolism. [7] In a circular cycle, there is nearly no waste and almost everything is re-used. Girardet characterizes this as a natural world process. On the other hand, a 'linear' metabolism which is characterized as an urban world process has a clear resource in-put and waste out-put. Girardet emphasizes that the accelerated use of linear metabolisms in urban environments is creating an impending global crisis as cities grow.

More recently the metabolism frame of reference has been used in the reporting of environmental information in Australia where researchers such as Newman have begun to link urban metabolic measures to and it has been suggested that it can be used to define the sustainability of a city within the ecosystems capacity that can support it. [8] This research has stayed mainly at a descriptive level and did not reach into the political or social forces of urban form and stages of flow. [1] From this research there has been a strong theme in present literature on urban sustainability is that of the need to view the urban system as a whole if we are to best understand and solve the complex problems. [5]

Two main schools of approach

The energy method

Energy Systems Symbols H.gif

Developed in 1970s Howard T. Odum, a systems ecologist, wanted to emphasize the dependence on the source of almost all energy on the planet: the sun. [6] Odum believed that previous research and development on urban metabolism was missing and did not account for qualitative differences of mass or energy flows. Odum's study took this into count and he coined the term "emergy" to track and account for the metabolic flows by measuring the solar energy used directly or indirectly to make a product or deliver a service. This method also emphasizes the use of a standard unit of measurement to calculate energy, nutrient and waste movement in the biophysical system; the unit chosen was "solar equivalent joules" (sej). At first glance, the notion to use standard units seems like a beneficial idea for calculating and comparing figures; in reality the ability to convert all urban processes into solar energy joules has proven to be a difficult feat, and difficult to understand. [1]

Material flow analysis

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Currently, the Urban Metabolism (UM) approach, as deducted from international literature, has been applied several times to assess and describe urban flows and impacts related to them, using different tools such as Material Flow Analysis (MFA) (Ioppolo et al., 2014). [9] The MFA, researched by Baccinni and Brunner in the 1990s, "measures the materials flowing into a system, the stocks and flows within it, and the resulting outputs from the system to other systems in the form of pollution, waste, or exports." [1] Much like Wolmans case model for a hypothetical American City, this method is based on the concept that the mass of the resources used will equal the mass "plus" stock changes out. [1] The MFA technique has become the mainstream school of urban metabolism because it uses more practical units that the public, workers, government officials and researchers can understand. [6]

Applications

There are four main uses of urban metabolism that are used today by urban planners and designers; sustainability reporting, urban greenhouse gas accounting, mathematical modelling for policy analysis and urban design.

Sustainability indicators

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With the issue of sustainability at the core of many environmental issues today, one of the main uses of Urban Metabolism in the modern era is to track and record levels of sustainability in cities and regions around the world. Urban metabolism collects important and very useful information about energy efficiency, material cycling, waste management and infrastructure in urban environments. The urban metabolism model records and analyzes environmental conditions and trends which are easily understood for policy makers and consequently comparable over time [6] making it easier to find unhealthy patterns and develop a plan of action to better the level of sustainability.

Greenhouse gas accounting

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Staying in line with the notion of sustainability, urban metabolism is also a helpful tool for tracking greenhouse gas emissions on a city or regional level. As mentioned above, with the proliferation of linear metabolisms such as cars, the production of greenhouse gases has increased exponentially since the birth and mass production of the automobile causing a problem for our atmosphere. [7] Urban metabolism has been proven to be a necessary tool for measuring levels of greenhouse gas because it is an out-put or waste product that is produced through human consumption. The model provides quantifiable parameters which allow officials to mark unhealthy levels of GHG emissions and again, develop a plan of action to lower them. [6]

Mathematical models

Aside from the two accounting applications above, urban metabolism has begun to develop mathematical models to quantify and predict levels of particles and nutrients within the urban metabolism model. Such models have mostly been created and used by MFA scholars and are helpful in determining present and future sub-processes and material stocks and flows within the urban environment [6] With the ability to predict future levels, these mathematical models allow progress to be made and possible pollution prevention programs to be instated rather than end-of-the-pipe solutions which have been favoured in the past. [10]

Design tools

Through utilization of the 3 applications above, scholars and professionals are able to use urban metabolism as a design tool to create greener and more sustainable infrastructure from the beginning. By tracing flows of energy, materials and waste through urban systems as a whole, changes and alterations can be made to close the loops to create circular metabolisms where resources are recycled and almost no waste is produced. [6] Such initiatives are being made around the world with technology and inventions which make building green that much easier and accessible.

Uses of the model are however not restricted to strictly functional analysis, as the model has been adapted to examine the relational aspects of urban relationships between infrastructure and citizens. [11]

See also

Related Research Articles

Industrial ecology (IE) is the study of material and energy flows through industrial systems. The global industrial economy can be modelled as a network of industrial processes that extract resources from the Earth and transform those resources into products and services which can be bought and sold to meet the needs of humanity. Industrial ecology seeks to quantify the material flows and document the industrial processes that make modern society function. Industrial ecologists are often concerned with the impacts that industrial activities have on the environment, with use of the planet's supply of natural resources, and with problems of waste disposal. Industrial ecology is a young but growing multidisciplinary field of research which combines aspects of engineering, economics, sociology, toxicology and the natural sciences.

<span class="mw-page-title-main">Zero waste</span> Philosophy that encourages the redesign of resource life cycles so that all products are reused

Zero waste is a set of principles focused on waste prevention that encourages redesigning resource life cycles so that all products are repurposed and/or reused. The goal of the movement is to avoid sending trash to landfills, incinerators, oceans, or any other part of the environment. Currently 9% of global plastic is recycled. In a zero waste system, all materials are reused until the optimum level of consumption is reached.

Emergy is the amount of energy consumed in direct and indirect transformations to make a product or service. Emergy is a measure of quality differences between different forms of energy. Emergy is an expression of all the energy used in the work processes that generate a product or service in units of one type of energy. Emergy is measured in units of emjoules, a unit referring to the available energy consumed in transformations. Emergy accounts for different forms of energy and resources Each form is generated by transformation processes in nature and each has a different ability to support work in natural and in human systems. The recognition of these quality differences is a key concept.

<span class="mw-page-title-main">Metabolic rift</span> Marxist conception of capitalist ecological crisis

Metabolic rift is Karl Marx's key conception of ecological crisis tendencies under capitalism, or in Marx's own words, it is the "irreparable rift in the interdependent process of social metabolism". Marx theorized a rupture in the metabolic interaction between humanity and the rest of nature emanating from capitalist agricultural production and the growing division between town and country.

Environmental accounting is a subset of accounting proper, its target being to incorporate both economic and environmental information. It can be conducted at the corporate level or at the level of a national economy through the System of Integrated Environmental and Economic Accounting, a satellite system to the National Accounts of Countries.

Cleaner production is a preventive, company-specific environmental protection initiative. It is intended to minimize waste and emissions and maximize product output. By analysing the flow of materials and energy in a company, one tries to identify options to minimize waste and emissions out of industrial processes through source reduction strategies. Improvements of organisation and technology help to reduce or suggest better choices in use of materials and energy, and to avoid waste, waste water generation, and gaseous emissions, and also waste heat and noise.

Anthropogenic metabolism, also referred to as metabolism of the anthroposphere, is a term used in industrial ecology, material flow analysis, and waste management to describe the material and energy turnover of human society. It emerges from the application of systems thinking to the industrial and other man-made activities and it is a central concept of sustainable development. In modern societies, the bulk of anthropogenic (man-made) material flows is related to one of the following activities: sanitation, transportation, habitation, and communication, which were "of little metabolic significance in prehistoric times". Global man-made stocks of steel in buildings, infrastructure, and vehicles, for example, amount to about 25 Gigatonnes, a figure that is surpassed only by construction materials such as concrete. Sustainable development is closely linked to the design of a sustainable anthropogenic metabolism, which will entail substantial changes in the energy and material turnover of the different human activities. Anthropogenic metabolism can be seen as synonymous to social or socioeconomic metabolism. It comprises both industrial metabolism and urban metabolism.

Material flow analysis (MFA), also referred to as substance flow analysis (SFA), is an analytical method to quantify flows and stocks of materials or substances in a well-defined system. MFA is an important tool to study the bio-physical aspects of human activity on different spatial and temporal scales. It is considered a core method of industrial ecology or anthropogenic, urban, social and industrial metabolism. MFA is used to study material, substance, or product flows across different industrial sectors or within ecosystems. MFA can also be applied to a single industrial installation, for example, for tracking nutrient flows through a waste water treatment plant. When combined with an assessment of the costs associated with material flows this business-oriented application of MFA is called material flow cost accounting. MFA is an important tool to study the circular economy and to devise material flow management. Since the 1990s, the number of publications related to material flow analysis has grown steadily. Peer-reviewed journals that publish MFA-related work include the Journal of Industrial Ecology, Ecological Economics, Environmental Science and Technology, and Resources, Conservation, and Recycling.

Material flow accounting (MFA) is the study of material flows on a national or regional scale. It is therefore sometimes also referred to as regional, national or economy-wide material flow analysis.

Industrial metabolism is a concept to describe the material and energy turnover of industrial systems. It was proposed by Robert Ayres in analogy to the biological metabolism as "the whole integrated collection of physical processes that convert raw materials and energy, plus labour, into finished products and wastes..." In analogy to the biological concept of metabolism, which is used to describe the whole of chemical reactions in, for example, a cell to maintain its functions and reproduce itself, the concept of industrial metabolism describes the chemical reactions, transport processes, and manufacturing activities in industry.

Ecological design or ecodesign is an approach to designing products and services that gives special consideration to the environmental impacts of a product over its entire lifecycle. Sim Van der Ryn and Stuart Cowan define it as "any form of design that minimizes environmentally destructive impacts by integrating itself with living processes." Ecological design can also be defined as the process of integrating environmental considerations into design and development with the aim of reducing environmental impacts of products through their life cycle.

The establishment of industrial ecology as field of scientific research is commonly attributed to an article devoted to industrial ecosystems, written by Frosch and Gallopoulos, which appeared in a 1989 special issue of Scientific American. Industrial ecology emerged from several earlier ideas and concepts, some of which date back to the 19th century.

This page is an index of sustainability articles.

<span class="mw-page-title-main">Circular economy</span> Regenerative system in which resource input and waste, emission, and energy leakage, are minimised

A circular economy is a model of production and consumption, which involves sharing, leasing, reusing, repairing, refurbishing and recycling existing materials and products for as long as possible. CE aims to tackle global challenges such as climate change, biodiversity loss, waste, and pollution by emphasizing the design-based implementation of the three base principles of the model. The three principles required for the transformation to a circular economy are: designing out waste and pollution, keeping products and materials in use, and regenerating natural systems." CE is defined in contradistinction to the traditional linear economy. The idea and concepts of circular economy (CE) have been studied extensively in academia, business, and government over the past ten years. CE has been gaining popularity because it helps to minimize emissions and consumption of raw materials, open up new market prospects and principally, increase the sustainability of consumption and improve resource efficiency.

<span class="mw-page-title-main">Social metabolism</span> Study of materials and energy flows between nature and society

Social metabolism or socioeconomic metabolism is the set of flows of materials and energy that occur between nature and society, between different societies, and within societies. These human-controlled material and energy flows are a basic feature of all societies but their magnitude and diversity largely depend on specific cultures, or sociometabolic regimes. Social or socioeconomic metabolism is also described as "the self-reproduction and evolution of the biophysical structures of human society. It comprises those biophysical transformation processes, distribution processes, and flows, which are controlled by humans for their purposes. The biophysical structures of society and socioeconomic metabolism together form the biophysical basis of society."

Resource recovery is using wastes as an input material to create valuable products as new outputs. The aim is to reduce the amount of waste generated, thereby reducing the need for landfill space, and optimising the values created from waste. Resource recovery delays the need to use raw materials in the manufacturing process. Materials found in municipal solid waste, construction and demolition waste, commercial waste and industrial wastes can be used to recover resources for the manufacturing of new materials and products. Plastic, paper, aluminium, glass and metal are examples of where value can be found in waste.

Eco-industrial development (EID) is a framework for industry to develop while reducing its impact on the environment. It uses a closed loop production cycle to tackle a broad set of environmental challenges such as soil and water pollution, desertification, species preservation, energy management, by-product synergy, resource efficiency, air quality, etc.

MuSIASEM or Multi-Scale Integrated Analysis of Societal and Ecosystem Metabolism, is a method of accounting used to analyse socio-ecosystems and to simulate possible patterns of development. It is based on maintaining coherence across scales and different dimensions of quantitative assessments generated using different metrics.

A circular economy is an alternative way countries manage their resources, where instead of using products in the traditional linear make, use, dispose method, resources are used for their maximum utility throughout its life cycle and regenerated in a cyclical pattern minimizing waste. They strive to create economic development through environmental and resource protection. The ideas of a circular economy were officially adopted by China in 2002, when the 16th National Congress of the Chinese Communist Party legislated it as a national endeavour, though various sustainability initiatives were implemented in the previous decades starting in 1973. China adopted the circular economy due to the environmental damage and resource depletion that was occurring from going through its industrialization process. China is currently a world leader in the production of resources, where it produces 46% of the worlds aluminum, 50% of steel and 60% of cement, while it has consumed more raw materials than all the countries a part of the Organisation for Economic Co-operation and Development (OECD) combined. In 2014, China created 3.2 billion tonnes of industrial solid waste, where 2 billion tonnes were recovered using recycling, incineration, reusing and composting. By 2025, China is anticipated to produce up to one quarter of the worlds municipal solid waste.

Stephanie Pincetl is an American academic specializing in the intersection of urban policy and the environment, particularly in California. She is the Director of the UCLA Center for Sustainable Urban Systems in Los Angeles.

References

Notes

  1. 1 2 3 4 5 6 Pincetl, S., Bunje, P., & Holmes, T. (2012). An expanded urban metabolism method: Toward a systems approach for assessing urban energy processes and causes. Landscape and Urban Planning, 193-202.
  2. 1 2 Kennedy, C., Cuddihy, J., & Engel-Yan, J. (2007). The changing metabolism of cities. Journal of Industrial Ecology, 11(2), 43-59.
  3. 1 2 Fischer-Kowalski, M. (1998). Society's metabolism the intellectual history of materials flow analysis, part I, I 860- I 970. Journal of Industrial Ecology, 2(1), 61-78.
  4. 1 2 McDonald, G. W., & Patterson, M. G. (2007). Bridging the divide in urban sustainability: From human exemptionalism to the new ecological paradigm.Urban Ecosyst, 10, 169-192
  5. 1 2 Decker, E., Elliot, S., Smith, F., Blake, D., & Rowland, F. S. (2000). Energy and material flow through the urban ecosystem. Energy Environment, 25, 685-740.
  6. 1 2 3 4 5 6 7 8 Kennedy, C., Pincetl, S., & Bunje, P. (2011). The study of urban metabolism and its applications to urban planning and design. Environmental Pollution,159, 1965-1973.
  7. 1 2 3 4 Wachsmuth, D. (2012). Three ecologies: Urban metabolism and the society-nature opposition. The Sociological Quarterly, (53), 506-523.
  8. Newman, P. (1999). Sustainability and cities: Extending the metabolism model. Landscape and Urban Planning, (44), 219-226.
  9. Ioppolo, Giuseppe; Reinout Heijungs, Stefano Cucurachi, Roberta Salomone, and René Kleijn, 2014. Urban Metabolism: Many Open Questions for Future Answers. Pp 23-32 in Pathways to Environmental Sustainability, eds. Roberta Salomone and Giuseppe Saija. Springer.
  10. Cleaner production versus end-of-pipe. (n.d.). Retrieved from http://www.centric.at/services/cleaner-production/cleaner-production-versus-end-of-pipe
  11. Gandy, M. (2004). Rethinking urban metabolism: Water, space and the modern city. City, http://www.geog.ucl.ac.uk/about-the-department/people/academics/matthew-gandy/files/pdf2.pdf

Bibliography