Urban metabolism is a

model A model is an informative representation of an object, person or system. The term originally denoted the plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin ''modulus'', a measure. Models c ...

to facilitate the description and analysis of the flows of the materials and

energy In physics, energy (from Ancient Greek: ἐνέργεια, ''enérgeia'', “activity”) is the quantitative property that is transferred to a body or to a physical system, recognizable in the performance of work and in the form of hea ...

within

cities A city is a human settlement of notable size.Goodall, B. (1987) ''The Penguin Dictionary of Human Geography''. London: Penguin.Kuper, A. and Kuper, J., eds (1996) ''The Social Science Encyclopedia''. 2nd edition. London: Routledge. It can be def ...

, such as undertaken in a

material flow analysis 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 o ...

of a city. It provides researchers with a metaphorical framework to study the interactions of natural and human systems in specific regions.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. 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."Kennedy, C., Cuddihy, J., & Engel-Yan, J. (2007). The changing metabolism of cities. Journal of Industrial Ecology, 11(2), 43-59. With the growing concern of

climate change In common usage, climate change describes global warming—the ongoing increase in global average temperature—and its effects on Earth's climate system. Climate change in a broader sense also includes previous long-term changes to ...

and atmospheric

degradation Degradation may refer to: Science * Degradation (geology), lowering of a fluvial surface by erosion * Degradation (telecommunications), of an electronic signal * Biodegradation of organic substances by living organisms * Environmental degradatio ...

, 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 Holism () is the idea that various systems (e.g. physical, biological, social) should be viewed as wholes, not merely as a collection of parts. The term "holism" was coined by Jan Smuts in his 1926 book '' Holism and Evolution''."holism, n." OED On ...

viewpoint to encompass all of the activities of a city in a single model.

History

With deep roots in

sociology Sociology is a social science that focuses on society, human social behavior, patterns of social relationships, social interaction, and aspects of culture associated with everyday life. It uses various methods of empirical investigation an ...

Karl Marx Karl Heinrich Marx (; 5 May 1818 – 14 March 1883) was a German philosopher, economist, historian, sociologist, political theorist, journalist, critic of political economy, and socialist revolutionary. His best-known titles are the 1848 ...

and fellow researcher

Friedrich Engels Friedrich Engels ( ,"Engels"
'' 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. 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.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 Through his experimental study of

urbanization Urbanization (or urbanisation) refers to the population shift from rural to urban areas, the corresponding decrease in the proportion of people living in rural areas, and the ways in which societies adapt to this change. It is predominantly t ...

he established a physical budget for urban energy and material throughput by way of an input output table. 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. :"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." It wasn't until 1965 when

Abel Wolman Abel Wolman (June 10, 1892 – February 22, 1989) was an American engineer, educator and pioneer of modern sanitary engineering. His professional career left impacts in academia, sanitary engineering research, environmental and public health serv ...

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. 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. 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. The model allows the monitoring and documentation of natural resources used (mainly water) and the consequential creation and out-put of waste.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. 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.Wachsmuth, D. (2012). Three ecologies: Urban metabolism and the society-nature opposition. The Sociological Quarterly, (53), 506-523. 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. Girardet laid the foundation for the

industrial ecology 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 resource ...

approach to urban metabolism in which it is seen as the "conversion of nature into society." Aside from being a great advocate and populariser for urban metabolism, Girardet significantly coined and drew the difference between a 'circular' and 'linear' metabolism. 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.Newman, P. (1999). Sustainability and cities: Extending the metabolism model. Landscape and Urban Planning, (44), 219-226. 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. 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.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.

Two main schools of approach

The energy method

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. Odum believed that previous research and development on urban metabolism was missing and did not account for qualitative differences of

mass Mass is an intrinsic property of a body. It was traditionally believed to be related to the quantity of matter in a physical body, until the discovery of the atom and particle physics. It was found that different atoms and different eleme ...

or energy flows. Odum's study took this into count and he coined the term "

emergy 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 pr ...

" 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.

Material flow analysis

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). 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." 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. 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.

Applications

There are four main uses of urban metabolism that are used today by urban planners and designers; sustainability reporting, urban

greenhouse gas accounting Greenhouse gas accounting or Carbon accounting is a framework of methods to measure and track how much greenhouse gas (GHG) an organization emits or takes actions to reduce. Corporations, cities and other groups use these techniques to help limi ...

, mathematical modelling for policy analysis and urban design.

Sustainability indicators

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 Material is a substance or mixture of substances that constitutes an object. Materials can be pure or impure, living or non-living matter. Materials can be classified on the basis of their physical and chemical properties, or on their geologi ...

waste management Waste management or waste disposal includes the processes and actions required to manage waste from its inception to its final disposal. This includes the collection, transport, treatment and disposal of waste, together with monitorin ...

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 making it easier to find unhealthy patterns and develop a plan of action to better the level of sustainability.

Greenhouse gas accounting

Staying in line with the notion of sustainability, urban metabolism is also a helpful tool for tracking

greenhouse gas emissions Greenhouse gas emissions from human activities strengthen the greenhouse effect, contributing to climate change. Most is carbon dioxide from burning fossil fuels: coal, oil, and natural gas. The largest emitters include coal in China and ...

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. 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.

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 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.Cleaner production versus end-of-pipe. (n.d.). Retrieved from http://www.centric.at/services/cleaner-production/cleaner-production-versus-end-of-pipe

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. 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.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

References

Notes

Bibliography

* Baccini, P. (2007). A city's metabolism: Towards the sustainable development of urban systems. Journal of Urban Technology, 4(2), 27-39. * Boyle, H. G. (1994). Metropolitan food systems in developing countries: The perspective of "urban metabolism". GeoJournal, 34(3), 245-251. * Cleaner production versus end-of-pipe. (n.d.). Retrieved from http://www.centric.at/services/cleaner-production/cleaner-production-versus-end-of-pipe * 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. * 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. * Kennedy, C., Cuddihy, J., & Engel-Yan, J. (2007). The changing metabolism of cities. Journal of Industrial Ecology, 11(2), 43-59. * 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. * 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. * Newman, P. (1999). Sustainability and cities: Extending the metabolism model. Landscape and Urban Planning, (44), 219-226. * 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. *State of the Environment Advisory Council. (1996). ''State of the Environment Report 1996'': CSIRO. * Wachsmuth, D. (2012). Three ecologies: Urban metabolism and the society-nature opposition. The Sociological Quarterly, (53), 506-523. * Wolman, A. (1965). ''The metabolism of cities.'' Scientific American, 213(3),179-190.

External links

"Urban Metabolism"
- Encyclopedia of the Earth article
Metabolism of Cities
- Research hub with publications, datasets and tools related to urban metabolism {{DEFAULTSORT:Urban Metabolism Environmental impact assessment Industrial ecology Environmental social science concepts