Defining urban metabolism

“the sum total of the technical and socio-economic processes that occur in cities,

resulting in growth, production of energy, and elimination of waste” (Kennedy et al., 2007).

Origins of concept• Karl Marx first discussed urban metabolism in 1883, and used

the concept to describe the material and energy exchanges between nature and society in his critique of industrialization (Marx, 1981).

• Later, Wolman (1965) re-launched the urban metabolism concept in response to deteriorating air and water qualities in American cities.

• As we see, concept emerged out of desıre to quantıfy, ın order to change/ımprove.

• The concept has a crıtıcal aspect

Why we need ıt

• The majority of the planet live in cities• The metabolism of these cities is

accelerating=greater ımpact on envıronment and qualıty of lıfe, health etc.

• Metabolısm ıs hıgh because our buıldıngs and cıtıes are resource-ıntensıve and ıneffıcıent

• Understandıng and regulatıng metabolısm ıs a fırst step ın movıng towards sustaınabılıty

World water & energy use on rise

Our buildings are very energy-intensive

• In some respects the city is like a plant stretching its roots out further and further until its resource needs are satısfıed

• One aspect of this growth is that cities require greater expenditure of transportation energy as materials travel from increasing distances.

Sustaınabılıty

• Development today that does not prevent development tomorrow (Bruntland Report for UN, 1987 Our Common Future)

• In metabolısm terms: the cıty (or buıldıng) does not use more resources, and produce more waste, than the envıronment can provıde/absorb

• Metabolısm makes us more aware of our footprınt

The global trend is on the rise

Rising CO2 emissions

Benefıts of metabolısm concept

• Mathematical modelling is possible

Comparison is possible

The concept and tools of metabolısm make research ınto buıldıngs, cıtıes and the envıronment scıentıfıc and objectıve

Thıs can form the basıs for scıentıfıc, ratıonal polıcıes

Inputs

• Cities need to acquire resources to grow• These resources are, for example, water, energy,

construction materials etc.• Different strategies & methods are used to acquire

resources• Transformations occur within city and beyond due to

these processes• Many cities are getting more and more inputs from

further and further away=regıonal and global impacts

Water• The bıggest ınput by far• Wolman’s calculations for the 1960s for a one million-

person U.S. city estimated the input of water at 625,000 tonnes per day compared to just 9,500 tonnes of fuel and 2,000 tonnes of food.

• Most of this inflow is discharged as wastewater,with the remainder being lost by activities such as the watering of lawns.Other losses are from leaks: ın London, 28% of water supply ıs lost that way!

Consequences of rısıng water metabolısm

• Subsıdence• Salt water ınfıltratıon• Rısıng water tables that threaten buıldıngs’ foundatıons• Increasıngly polluted water supplıes • Need for cıtıes to go further and further away to fınd

‘clean’ supplıes • Impact of cıtıes further and further downstream• Hıstorıcal and contemporary conflıcts around water

acquısıtıon and use

Energy

• Cities need supplies of energy, but also produce energy through heat

• Thıs is a circular mechanism wıth feedback effects: the more energy used, the more heat produced; the more heat, the more need for energy to cool etc.

• Energy acquired from further and further away, wıth increasing global impacts

Urban heat island

Rising energy use and inefficiencies

• For U.S. Cities with populations greater than 100,000, peak electricity loads increase by about 1% for every

degree Celsius increase in temperature.

• In Toronto, a 1◦C increase on summer dayscorresponds to roughly a 1.6% increase in peakelectricity demand. Hot summer days are criticalin Toronto in that they cause the highest electricitydemand throughout the year.

Example with buildings

• Ubiquitous glass/steel/air conditioning is not an efficient form!

• Introduction of ‘smart technologies’ does not necessarily improve buıldings’ energy use profiles

• Technology does not do anything by itself; have to take into account how people use tech

• It is more effective to implement passive design principles

Materıals• Cities, like buildings, are made of materials; they are assemblages that

have taken place over time and space• These assemblages are complex and not always very rational or efficient:

cities present a certain amount of chaos, of the unplanned• Materıals have their own ‘life’ and can influence how we live in buildings

and cities; it is wrong to think that materials are ‘neutral’!

• In 1997, Hong Kong’s daily material inputs included 363 tonnes of glass; 3,390 tonnes of plastics; 9,822 tonnes of cement; 2,095 tonnes of wood;7,240 tonnes of iron and steel; and 2,768 tonnes of paper.

Relative to 1971, inputs of plastics had risen by 400%; iron and steel increased by close to 300%; cement and paper inputs were both up by 275%; and wood inputs had more than doubled. In comparison, the population only rose by78%.

-material input to Vienna is also upward. In most decades prior to the 1970s, the per capita use ofconstruction materials was 0.1 m3/yr (the 1930s being a significant exception at 1.4 m3/cap/yr).The volumes of input in the 1970s, 1980s, and 1990s, however, were 2.4, 3.3, and 4.3 m3/cap/yr,respectively (Brunner and Rechberger 2004).Upward per capita trends, for the period 1992 and 2001, were also estimated for direct materialinput and domestic material consumption for theCity of Hamburg (Hammer et al. 2003).

This evidence suggests that cities are becoming increasingly material-intensive.

Throughputs

• Cities use the resources they acquire in very specific ways, that are linked to local geography, history, culture and political power structures

• Resources are transformed in the city• The built environment—buildings, streets etc.– is the

result of these transformations• The built environment also shapes future

transformations• The management of resources also influences evolution

of socio-political dynamics in the city

Cities are spaces of unevenness and inequalities in resource use/access

• The resources acquired by cities do not flow evenly to all the citizens

• Theır flow reflects existing ınequalitıes, reınforces them, and creates new ones

• The networks buılt to carry resources reflect these relatıonshıps of power and dıscrımınatıon

• Dynamıcs of segregatıon/fragmentatıon are at work

Examples

• İnequality in access to water and power, sewerage

• İnequality in access to transport• İnequality in access to amenities• Networks bypass certain parts of cities (the

poorer, least powerful ones) in favour of others (the rıcher, more powerful ones)

Water

• Same issues with transportation, energy etc.

Constraints of geography (place) and history (time)

• The way cities acquire and distribute resources ıs constraıned by geography

• Hıstory also ımposes constraınts, for ınstance technologıcal and scıentıfıc

• Therefore, the unıversal, always-on networked access we enjoy ın developed world ıs very new and very fragıle

• Case of Los Angeles: small town in desert in 19th century, needed water to grow—no water, no growth possible

• Acquisition of water was only possible through technology of aqueducts, pumping systems etc

• Cities in arid climates such as Dubai only possible with cheap energy and desalination technology

• Most modern buildings only possible with invention of air conditioning

• etc

Use of resources reflects specific local political and cultural factors

• Oligarchy in LA: rise of a small group of powerful businessmen who were intent on growing the city to sell land, as well as developing their political influence

• Racism/colonial city in Cape Town: clean, piped water was only provided to white neighbourhoods, black areas were neglected; goal was asserting ‘superiority’ of the white

The built environment is the result of resource transformatıon, but also structures future dynamıcs

• Los Angeles could only grow with acquisition of water from far away sources; but the more it grew, the more water it then needed...

• In Cape Town, racial divisions were entrenched by differing access to water, power networks: disriminated socially, politically, but also unconnected.

• The policies around resources and networks are inscribed into built environment for a long time

Outputs

• Outputs are what occur as a consequence of the consumption of resources.

• Waste and pollution are two big categories of outputs

• Outputs need to be either re-used, or evacuated from the city

• Linear vs circular/closing of loops• Like inputs, outputs can have global impact

Waste and pollution

• Cities generate significant quantities of waste, and this trend is increasing

• Waste is defined as ‘matter out of place’: materials that are unwanted and/or unused, and require elimination/removal, otherwise they would block metabolism

• Waste was historically the first driver of network construction: sanitation systems, water systems to remove waste and avoid contaminating water supplies

Pollution/emissions

• A rising category of waste, but with global repercussions this time

• The challenge is to make cities that have a less marked global impact, such as on climate

Some major studies and their results

• Brussels : ecologists Duvigneaud and Denaeyer-De Smet (1977), which included quantification of urban biomass and even organic discharges from cats and dogs!

• Hong Kong, Newcombe and colleagues (1978) were able to determine inflows and outflows of construction materials and finished goods. An update of the Hong Kong study by Warren-Rhodes and Koenig (2001) showed that per capita food, water, and materials consumption had increased by 20%, 40%, and 149%, respectively—from 1971 to 1997.

• Sydney, 1999, Newman. Introduced notıon of qualıty of life and wellbeing into analysis of metabolism

The metabolism of Brussels

Summary

• Metabolısm of cities and buildings is essentially linear, and therefore inefficient and wıth negative externalities

• We need to fınd ways of closing loops, to make all these cycles as local as possible

• Tools from planning and urban climate science can help us design better buildings and cities, but we also have to understand how people use buildings and cities

Re-use or flush out? Linear vs circular

• Modern cities & buildings have linear metabolisms: they draw in resources, and produce waste, emissions.

• The cost of their existence is spread out over rest of cities or surrounding areas, even the world.

• Closing loops can help improve this

How to change the metabolism of the built environment?

• More efficient, better designed buildings• Denser, more compact cities featuring a mix of

uses. Reducing need for transport and energy• A general change in mentalities and lifestyles,

and a redefinition of the city around new principles

Policies: certification programmes

• Standards can help steer building industry towards adoption of sustainability (=making their metabolism less intensive and less linear)

• Standards are not enough by themselves though

LEED: Leadership in Energy & Environmental Design

• Developed by USGBC in 1998• Help building owners and developers achieve environmental

responsibility and resource efficiency• Applied to more than 7,000 projects in US and 30 countries• LEED offers exams to certify professionals• Several factors are assessed: water efficiency, energy and

atmosphere, materials and resources, indoor environment quality etc.

• 4 levels: Certified, Silver, Gold, Platinum

Benefits of LEED

• Better working environment for workers= less sickness, more productive workers etc

• Lower operating costs, because building uses less energy, water etc.

• Lower impact on city/neighbourhoord due to lower resource use

Limits of LEED• Not site-specific: if a building saves water in wet region, it gets same

points as building in dry region• Not energy-specific: only efficiency in energy use is measured, developers

are free to choose which type of energy they use (i.e. conventional vs. renewable)

• Developers can target easy points to get certified: quality indoor spaces, educational displays all score points, but don’t necessarily make buildings better for environment

Examples of LEED buildings

Other certification programmes

• BREEAM: created in 1990 in UK. World’s largest and oldest programme, over 250,000 buildings worldwide certified

• BREEAM also exists for planned communities, so goes beyond the scale of the building

• Certification programmes raise awareness of sustainable design among developers, building owners, and people in general

• Certification programmes demonstrate that sustainability is not an extra cost, that it can reduce the cost of operating a building

• However, certification programmes can be manipulated to score points

• Programmes only measure improvement over traditional design; they encourage incremental change, not profound change

Towards denser settlements

• Density is seen by many experts as more efficient than spread out cities

• Reducing energy use for the post-oil city• Promoting vital, dynamic, mixed

neighbourhoods

Density means lower energy use per capita

But density is not answer in itself

• If we maintain the same kind of buildings we use today, even density is not enough to compensate for high energy use

• The embedded energy in what we consume remains high

• Density is not desired by everyone= issue of freedom

Urban housing also energy-intensive

Designing less energy-intensive buildings & communities

• Technologies. Not a silver bullet, but can help.• Passive design• Use of principles of urban climatology (siting,

natural air circulation, shading etc.) is a step further, and increases urban resilience.

Passive design

• Strong tradition in certain countries, such as Germany and Israel, growing in many others

• Focusing on the shell and structure of the building, not on technology

• Insulation, orientation, and ventilation are key factors in making homes more energy efficient and more comfortable

Principles of passive design

Examples

Climate-sensitive urban design• Contemporary architecture neglects local climatic realities, and

manufactures interior climates through energy-intensive air-conditioning and heating methods

• This causes pollution and can reduce comfort (dry air), and cuts us off from our environment even more

• Climate-sensitive design draws on local climatic knowledge, traditional design and building methods, to deliver buildings that require less energy and produce better comfort

• Furthermore, these buildings are often better looking and more interesting, as they draw on local, historical building traditions

Climate-sensitive design checklist• Takes into account orientation to the sun: maximise winter

sun (for warmth) in cold climates, or minimise sun exposure in hot climates

• Wind currents: for ventilation on hot days, for better air quality

• Use of water: as a cooling agent• Selection of natural, traditional building materials if possible, for instance

thatched roofs

Scalable to community level

• Principles of climate-sensitive design can also be applied to community planning, not just buildings

• Have to take into account how presence of multiple buildings changes air flows, exposure to sun, temperatures. etc

• This is why it is crucial to think of the context when designing buildings: materials, climate, water, people etc.

Street canyons

Climate maps and climate atlases

• Provide synthetic knowledge of main climatic data for a given city/region

• Planners, architects can use this information to adapt their work to context

• Very big in Germany (and Israel), for instance Stadtklima Stuttgart project. This is used actively by architects, planners and city government

• Also adopted in other cities, eg Manchester, UK, to inform future planning

Example: Manchester

Multiple approach to architecture, planning and climate

• Several programmes in the city aim to ensure climate change mitigation and adaptation.

• Work includes retrofitting older buildings so that they are more energy and water-efficient.

• Some of these projects take the shape of public-private partnerships (PPP), like EcoCities

• The goal is to reduce the city’s vulnerability to climate risk= probabilistic approach

Risk, mitigation, adaptation

Map of vulnerability and risk

Examples of adaptation

Examples of mitigation

A growing global movement

• Many associations work on climate and climate-sensitive urban design

• These associations involve architects, planners, decision-makers, and major players such as UN, WMO, WHO etc

• IAUC, IFHTP, CIB• Many cities are forming organizations to push

for sustainability and climate adaptation/mitigation: ICLEI, C40 etc.

Eco-villages and eco-quarters

• There are many cases of ‘eco-villages’ or ‘eco-quarters’ now applying the principles of climate-sensitive urban design (CSUD)

• These developments illustrate the use of concepts from urban metabolism to deliver sustainability

• Sustainable (urban) development is development today that does not impact the world in a negative way

An example of sustainable development in action: BedZED, United Kingdom

Features of BedZed• Integrates principles of passive housing design, climate-sensitive

urban design, sustainable urban planning. • Reduction of car use and access, emphasis on pedestrian life.

Buildings oriented to receive maximum sun light in winter and reduce heating bills. Very efficient insulation. Solar panels. Efficient passive ventilation systems ensure fresh, healthy air provision.

• Community features many green spaces and common areas to promote exercise and socialising, to improve health and community life.

• Rainwater is collected to water green areas and reduce use of potable water.

Currumbin EcoVillage, Queensland, Australia

• Strong emphasis on open space and preservation of nature (rainforest, wetlands). Wildlife corridors are preserved for species. Lots of walking and biking trails to promote these kinds of movement; cars are banned on most of the development.

• Houses are designed individually and uniquely by owners to encourage diversity.

• Houses feature solar panels, rainwater collection for drinking and watering= almost no importing of water or energy into development, almost self-sufficient.

• Also, a series of fruit & vegetable gardens encourage local production of food, as well as interaction between people around this activity.

• The village is centred around a community hall and activity centre, which encourages socialising and community life, as well as decisions about matters that concern the whole community.

• Combines environmental, social, quality of life aspects; sustainability is more than just ‘nature’

How to move away from linear metabolism

• CSUD not only tool to go towards more sustainable communites

• Producing a less linear metabolism requires closing loops of energy, water, nutrient use etc.

• This means, ultimately, a profound change in how we think of buildings/cities, a redefinition of the urban

Closing loops

• Slowing down metabolism and making it less linear

-Circular metabolisms are less resource-intensive; they also reconnect people with where their resources come from, and therefore, with their environment

Greening is an important tool

• Green surfaces have a cooling effect • They help in climate mitigation and adaptation• They increase quality of life and beauty of

urban areas• ‘edible city’: work opportunities, combating

obesity, reconnecting with nature• Green surfaces can improve water

management in cities

• Urban gardens provide fresh, local, (organic) food= healthier life, less impact on environment

• Spaces for socialising and interacting• Reconnection with the environment• Go against industrial food chains, which use

energy, pollute etc.• Employment opportunities, especially for

poorer/ discriminated populations• Architects, planners should make room for these

green areas when designing/building

• Green roofs and greening of areas between buildings have a cooling effect (adaptation)

• Absorb toxic substances in the air• Also mitigate CO2 emissions• Beautify the urban area: sense of pride and

wellbeing, relaxing with health benefits

Greening and urban water management

• Greening can be a powerful tool in improving urban water management

• Green surfaces slow water movement• They can purify polluted water• Help recharge underground water resources• Tool in flood prevention and

mitigation/adaptation

Greening as step towards sustainable urban drainage systems (SUDS)

In the future, maybe?

• Move from centralised systems for energy, water, food etc. provision to decentralised systems

From centralised systems…

…to de-centralised

• De-linking and de-coupling growth from negative env/soc aspects

• Doing things locally so that people realise their impact on the world and change their lifestyles

Optimising metabolism by closing loops

What does it look like?

Metabolism and sustainability

• Sustainability is a very important notion in architecture, design and planning today

• It’s also very present in political and social discourse, everyone claims it…

• …but what does it actually mean? And why should planners, architects, designers aim for it?

• Are there other notions that are more precise and more relevant? Is it just a fashion that will pass?

Sustainability’s connection to metabolism

• Metabolism describes flows and in particular use of resources and waste of cities

• Sustainability is concerned with improving these parameters, at the building and city levels, as well as planetary scale too

• Metabolism provides you with an intellectual tool to approach current talk of sustainability

Towards a definition

• An initial definition: development that can be sustained

• Not exceeding the environment’s carrying capacity, and leaving resources for future generations

• An environmental, economic and social content: sustainability is, ideally, reaching for a ‘triple bottom line’, the ‘three Es’.

How did this definition emerge?

• It is always important to understand how the concepts we use came about; this informs us of the unspoken aspects of the concept

• Emergence and evolution of the concept -forestry management from the 15-16th centuries-Silent Spring by Rachel Carson (1962)-Club of Rome (1972) and ‘limits to growth’-Bruntland Report (1987)

Who drives this agenda today?

• Global organısatıons are pushing for greater sustainability. For example, UN with Rio (1992), Kyoto, Rio+20 etc

• Cities are playing a big role in this: C40, ICLEI.• With governments abandoning or watering

down their commitments, cities are taking the lead

A degree of confusion

• Sustainability vs deep ecology, end of growth and de-growth currents

• The word is used a lot, and is in danger of losing any meanıng

• The economic aspect is beıng pushed to the detriment of other dimensions, leading to emergence of ‘sustainability light’

• When sustainability becomes ‘greenwashing’

Sustainability vs sustainability features

• Greenfield, isolated development cannot be sustainable, even if it has sustainability features

• The same goes for supposedly ‘revolutionary’ buildings that drive or enable unsustainable lifestyles

• The rise of such projects shows the tendency towards a diluted, reduced form of engagement with sustainability

• Moving towards sustainability implies thinking at the scale of the city and the region

Major debates in sustainability

• Sprawl vs compact development• Retrofit vs new-build • Which part of the 3 Es to prioritise? • Sustainability and urban resilience• Distinguishing between unsustainability,

segregation and fragmentation

The use of theories to guide us

• Theories, concepts are necessary to think better about realities, they are heuristic

• We will be looking at some major theories and debates around metabolism & sustainability in relation to architecture, design and planning

The main theories

• Urban political ecology• Actor-network theory• Ecological modernisation • Urban regime theory