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Circle Economy and ICLEI have partnered up to initiate the go to knowledge hub of case studies about the circular economy in cities. The Cities Collection is a repository of case studies that demonstrate the role of cities in the circular transition, and includes policies, business cases and research articles. Cases in the Collection flow into an ecosystem of digital products which support users in transitioning cities to circularity, for example [Ganbatte](https://ganbatte.world/cities/) and <a href="https://circulars.iclei.org/" target="_blank">ICLEI Circulars</a>, both part of the <a href="https://circulars.iclei.org/circle-lab-for-cities/" target = _blank">Circle Lab for Cities Programme.</a>

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Circular Cities

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Policy case

Impact on the availability of resources as well as their effect on living organisms, ecosystems, and components of the environment.

Ecological Impact

Impacts on the financial condition of a company, as well as the the economicconditions of its stakeholders and on economic systems at local, national, andglobal levels.

Economic Impact

Direct and indirect reduction in economic costs

Cost Savings

Reduced green house gas emissions released into the biosphere

Reduce Emissions (SDG13)

Reduced use of virgin materials and/or an increase of the use of secondary and bio-based materials

Reduce Material Consumption (SDG12)

Minimise waste through diversion: Instead of sending waste to landfill, it is redirected into other industrial processes for handling, treatment, recycling, recovery, or reuse in various forms. 

Minimise waste through design: At the outset of a process of project, plan and design such that there is zero waste or minimal waste during production, use, and at end of life. 

Minimise Waste (SDG12)

Reduced use of fossil fuel energy sources and/or increased use of renewable energy

Reduce Energy Consumption

Producing building materials and providing services to create residential and non-residential infrastructure and real estate


Construction and Infrastructure

Utilise bio-based, reusable, non-toxic and non-critical materials

Regenerative materials

Engage with the government on circular policies and programmes

Government collaboration

'Mobilise' sets the direction of and builds momentum towards long-term change, while also determining how this direction is determined and governed.

Mobilise

 Convene Towards Action

Advocate for circular change

Voluntary agreements around circular ambitions

Redesign systems to lay the foundation for circular activities and enable the transition to a circular economy 

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Rethink

The built environment, including housing, commercial buildings, and the necessary infrastructure for mobility, is essential for our livelihoods, but:
- the extraction of minerals used to produce construction materials is responsible for a quarter of global land use change,
- approximately 40% of global GHG emissions can be attributed to buildings’ construction, use and demolition, and
- construction and demolition processes drive nearly one-third of all material consumption. 

Making the built environment more circular must prioritise a heavy reduction in material use—while also closing the loop on materials and bringing secondary and renewable material choices to the fore. Our four key solutions for the built environment are:
- Make the most of what already exists: Make the most of existing materials by reusing, repurposing, upgrading and renovating following circular approaches. Where new builds are needed, use secondary materials and be as efficient as possible with urban planning solutions that follow circular design principles so that buildings can be reused, repurposed, and easily disassembled in the future.
- Be as energy efficient as possible: From the design phase, utilise circular strategies to create material- and energy efficient buildings. Couple these designs with a rollout of clean energy solutions, and prioritise energy-efficient appliances and retrofitting. 
- Utilise secondary materials: Maximise the high-value reuse of buildings and components where possible. Ideally, enable the utilisation of construction and demolition outputs and ensure that as much of it as possible is recycled to avoid the need for virgin materials, such as sand and gravel.
- Prioritise circular materials and approaches: Transition to using renewable wood, timber or cross-laminated timber instead of steel and concrete, or move to other locally available materials. Utilise mainstream modular construction and prioritise lightweight frames and structures to reduce cement and steel use, as well as green roofs where possible.



🏢 Built Environment

Businesses

Governments

Regenerate strategies phase out hazardous or toxic materials and processes and substitute them with regenerative biomass resources. A circular economy aims to mimic natural cycles—by shifting to more regenerative farming practices, for example—while also maximising the share of circular biomass that enters the economy. Regeneration can happen both at the systems level (by designing regenerative processes) as well as at the product level (by switching synthetic to organic fertilisers, for example).

Regenerate

Impacts

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Industries

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A framework of policy instruments that enabled and encourage the transition to the circular economy

Policy Instruments

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A framework of policy instruments that enable and stimulate the transition to the circular economy

The principles of a circular economy concern designing out waste, regenerating ecosystems and keeping items in use. Decoupling the economy from material flows—improving the rate of resource productivity faster than the economic growth rate—is also a consistent guide. By evolving with the growing number of applications of circular economy principles, and consolidating these strategies across thematic areas, Circle Economy’s Key Elements Framework (KE) renders the elements of the circular economy salient and serves as a basis to derive contextual strategies and interventions. 


The Framework consists of:
- Core Elements: Activities directly handling product or material flows; and uniquely,
- Enabling Elements: those that remove obstacles for core actors.


Key elements of the circular economy

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Circle Economy's framework of strategies and activities that define the circular economy

The Circular City Actions Framework provides urban changemakers with five complementary strategies they can use to start working towards a more circular system. 

The framework is action-based to provide users with concrete strategic directions and showcase the desired outcomes of each strategy. 
The framework consists of five complementary **strategies**, under which **sub-strategies** provide further detail. Finally, each sub-strategy consists of a diversity of tangible **solutions** which are framed in relation to key thematic areas. 

Note: solutions are currently focused on:
- 🍏 **Food systems**
- 🏢  **Built environment**
- 👕📱  **Consumer goods**
- ⚡ **Energy Systems**
- 🚌 **Mobility Systems**
- 💧 **Water Systems**

More thematic areas are coming soon...

'Click through each of the five strategy cards below to explore the framework and circular economy case studies in more depth!'



This framework was developed in collaboration with ICLEI, Metabolic and Ellen MacArthur Foundation with support from the MAVA Foundation. Read more about it [here]( https://circulars.iclei.org/action-framework/). 



Circular City Actions Framework

An action-based framework for local governments working towards circular cities

Thematic Areas

City Stakeholders

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Based on the work of [Bocken et al. (2016)](https://www.researchgate.net/publication/309699661_Product_design_and_business_model_strategies_for_a_circular_economy), the Four Flows Framework serves as a simple framework for managing resource flows in a circular economy by using less (Narrow), using for longer (Slow), using again (Cycle), and using clean, regenerative materials and energy (Regenerate).

These different principles of circular economy can be applied to our socioeconomic metabolism: we can design stocks like buildings, infrastructure, machinery, and vehicles to be rich resource mines for the future, and design manufactured goods and consumables to be cycled and made regenerative. Furthermore, the focus must also centre on getting more value out of fewer materials. Achieving the aims of a circular economy—minimising material use, regenerating the Earth, and preventing material losses—can be done through these four key strategies mentioned above.

Source: Circle Economy. (2023). *[The circularity gap report 2023](https://www.circularity-gap.world/2023)* (p.22). Amsterdam: Circle Economy. 

Four Flows Framework

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C40 research reveals changes to the construction industry could cut the emissions generated from buildings and infrastructure 44% by 2050. Copenhagen, Denmark (08 October 2019) — Research released today reveals changes to the construction industry could cut the emissions generated from buildings and infrastructure 44% by 2050. The report, published by C40 Cities, Arup and University of Leeds, Building and Infrastructure Consumption Emissions urges action in 6 key areas to reduce the climate impact of construction in cities:  Implementing efficiency in material design Enhancing existing building utilisation Switching high-emission materials to sustainable timber where appropriate Using lower-carbon cement Reusing building materials and components Using low, or zero-emission construction machinery  As well as reducing GHG emissions, the research reveals the additional economic, social and health benefits that ‘clean’ construction could generate. The interventions identified in the research would reduce air and noise pollution, providing health benefits for citizens and the environment. They would also spark change within the growing construction economy, providing opportunities for new jobs and skills. Cities are starting to take action on construction to address the climate impact of their consumption. Copenhagen, Oslo and Stockholm will now reduce the greenhouse gas emissions and air pollution from construction sites, in the effort to solve the climate crisis and improve public health. Frank Jensen, Lord Mayor of Copenhagen and Raymond Johansen, Governing Mayor of Oslo, today announced their ambition to reduce the use of fossil fuels in construction sites and civil works. The mayors pledged to enact regulations and/or planning policy to ensure they: Purchase biofuels and emission free machinery for the city’s own use Demand fossil-and emission-free solutions in public procurement and city supported projects In Oslo, all city-owned machinery and municipally or owned construction sites will operate with zero emissions by 2025. Copenhagen’s CPH2025 Climate Plan, roadmap 2017-2020, includes a goal for the City to use fossil-free fuels in its own non-road mobile machinery. In the budget for 2020 Copenhagen have decided to promote a transformation from fossil fuels to sustainable biofuels, and to fossil-free non-road mobile machinery in its own machines and strengthen efforts that municipally commissioned construction sites and civil work will be fossil-free. “Copenhagen will work to purchase fossil-free fuel for its own machinery and heavy vehicles, pilot projects with tender requirements for fossils-or emission-free construction machinery in construction projects,” said Frank Jensen, Lord Mayor of Copenhagen, and C40 Vice Chair. “We will also collaborate with market players to make them use fossil-free fuels.” “In Oslo, construction sites generate as much as 7 percent of total emissions, equivalent to an additional 30,000 petrol cars on the road,” said, Raymond Johansen, Governing Mayor of Oslo. “New kindergartens, schools, sports halls will in future be built emissions-free and with low climate materials. The building industry is our closest ally and an enthusiastic supporter. We are confident that by 2030 Oslo’s air will be cleaner, emissions lower and environment healthier thanks to the actions we are taking today.” Both cities have also pledged to reduce the indirect emissions generated from building works, through the prioritisation of retrofits and refurbishment of their existing stock, de-incentivizing demolitions, and encouraging the use of low-carbon and reusable materials. Stockholm is taking a holistic approach to reach the City’s goals to be fossil-fuel-free and climate positive by 2040. Together with the Swedish Construction Federation and the Swedish Environmental Research Institute IVL, Stockholm has developed a Life-Cycle Analysis tool to evaluate all aspects of the building process from a climate point of view – from the choice of materials and the use of machinery to the construction processes. Being now piloted the city aims at using it citywide form 2021. "Together with the building industry and academia Stockholm is creating a powerful tool to scrutinize the climate impact of the whole building process. Using it will help us steer towards the most climate efficient solutions”, said Anna König Jerlmyr, Mayor of Stockholm. Oslo, Copenhagen and Stockholm also commit to take a leadership role in creating a global market for low-emission construction materials and zero-emission machinery, working through the C40 Clean Construction Forum. Launched in Oslo in May 2019, the Forum brings together major cities from around the world to use their purchasing power to shift markets within the construction sector. "The world’s cities are growing fast, with an area the size of Milan being built every week. It may be a boom time for builders but the construction industry is a major contributor to the climate crisis,” said Mark Watts, Executive Director of C40 Cities. “The mayors of Oslo, Copenhagen and Stockholm recognise that without urgent action to cut emissions generated in the construction of buildings and infrastructure, there is no chance of delivering on the Paris Agreement and preventing catastrophic climate change. As C40’s research demonstrates, citizens will ultimately benefit from cleaner air, quieter streets and lower prices. Now it is up to businesses and industry to recognise the risks of inaction and work with mayors and consumers to make sure everyone benefits from the huge opportunities that lie ahead from clean construction.” Ben Smith, Energy and Climate Change Director, ARUP said: “As the sector responsible for the largest share of consumption-based emissions in C40 cities between now and 2050, it’s clear that the construction sector must do more to reduce its carbon impact. Our research shows that there are significant opportunities to act, but we need to rethink the way buildings and infrastructure are delivered. Making that change a reality will rely on working with all those with responsibility for delivering development. We believe that the construction sector can embrace this change, if it invests in necessary skills and training and seeks to promote innovation. Where this happens, the benefits go beyond emissions reduction – they are social, environmental and economic, cleaner air in cities, less noise and new job opportunities.” "Buildings are a cornerstone of our society. We spend over 90% of our time in buildings; people rely on them to survive; and they depend on the world’s finite resources to be built and operate. As they are responsible for nearly 40% of global carbon emissions, they also represent enormous potential in managing our remaining carbon budget” said Cristina Gamboa, CEO of the World Green Building Council. “At World Green Building Council, we are encouraged to see this important research from our partner C40. The opportunities it identifies for cities to address emissions from buildings and construction will support the sector's critical response to the climate emergency. Through our continued collaboration and World Green Building Council call for coordinated sector action to tackle embodied carbon, we believe there is a future of better and greener buildings for cities all over the world." Consumption-based emissions including construction, as well as food, clothing, aviation, building and others, from nearly 100 of the world’s big cities already represent 10% of global greenhouse gas emissions. Without urgent action, those emissions will nearly double by 2050. The full findings were laid out in a major piece of research  The Future of Urban Consumption in a 1.5°C World. This research was made possible with generous support from Citi Foundation. Mayors of more than 70 cities will meet in Copenhagen for the C40 World Mayors Summit 2019, October 09th-12th, to develop solutions to the global climate crisis. 

Copenhagen

Stockholm

Oslo

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City of Copenhagen

City of Stockholm

City of Oslo

Copenhagen, Oslo, and Stockholm released a joint pledge to reduce the greenhouse have emissions and air pollution from construction sites, in the effort to solve the climate crisis and improve public health. Six are the key areas to reduce the climate impact of construction in cities:- Implementing efficiency in material design- Enhancing existing building utilisation- Switching high-emission materials to sustainable timber where appropriate- Using lower-carbon cement- Reusing building materials and components- Using low, or zero-emission construction machinery (Source: C40's Clean Construction Policy Explorer)

Commitment to Clean Construction in Nordic cities

Reduced use and withdrawal of water and rate of recycling and reuse of water

Save Water (SDG6)

Providing electricity and gas services, including traditional and renewable energy generation, natural and manufactured gas and operating gas networks

Energy Utilities and Independent Power Producers

Providing water and sewage services, including water collection and distribution, water treatment systems and sewage treatment facilities

Water and Sewage

Collecting waste from households and businesses by means of refuse bins, wheeled bins, containers, etc., and providing treatment, incineration, materials recovery and reclamation, and disposal of hazardous and non-hazardous waste

Waste Management

Providing air, water, rail, and land transportation for passengers, such as airlines, airports, ferries, cruise-ships, tour boat operators, marine ports, railways, train stations, tour bus operators, vehicle rental, and taxi companies, travel agencies and related services

Passenger Transport Services

Ensure renewable, reusable, non-toxic resources are utilised as materials and energy in an efficient way

Prioritise regenerative resources

Utilise waste streams as a source of secondary resources and recover waste for reuse and recycling

Use waste as a resource

Account for the systems perspective during the design process, to use the right materials, to design for appropriate lifetime and to design for extended future use

Design for the future

Work together throughout the supply chain, internally within organisations and with the public sector and communities to increase transparency and create joint value

Team up to create joint value

Generating energy from waste through processes such as anaerobic digestion, gasification, incineration, etc.

Generating energy from waste

Recovering and reusing waste heat, gas, etc. for energy

Recovery and reuse of waste energy

Develop infrastructure to support resource cycling

Facilitate cross-collaboration by engaging city departments, industries and businesses on ambitious, closed-loop circular projects.

Support closed-loop systems and cross-sectoral synergies

Cities consume about 75% of global energy and emit between 50% and 60% of global greenhouse gases (UN-Habitat). To reduce the negative impact of their energy consumption, cities need to shift away from fossil fuels and move towards renewable energy sources. Such a shift will help cities work towards their climate change mitigation and adaptation action plans. Renewable energy technologies such as wind, water, solar, and geothermal can also help improve access to energy in vulnerable and marginalised neighbourhoods through, for example, decentralised, off-grid solutions.

Renewable energy technologies can harvest the energy in nature’s processes, such as wind, and solar radiation and geothermal heat, that can be replenished within a human lifespan. In contrast, fossil fuels are materials that are not replenished within a human lifespan and are combusted for energy, losing the fuel material and resulting in emissions.

Local governments can develop sustainable energy plans, considering different energy resources and requirements, to develop a robust strategy for the development of renewable energy technologies and infrastructure throughout the city. They can also institute specific legislation and tax systems to regulate energy production and consumption, incentivise research and development of cleaner, more efficient technologies. Via Power Purchase Agreements cities can buy renewable energy from green energy providers and fix the price in order to provide security to financial institutions to finance renewable energy infrastructure. Furthermore, increasing awareness and facilitating capacity-building on planning urban sustainable energy projects can help the uptake of clean energy across the city by different stakeholders—from citizens to businesses and institutions. Facilitating collaboration, then, will be crucial, since private companies operate most of the world’s energy systems.


⚡ Energy Systems

The demand for transport is rising globally—but current modes are heavily material- and fossil-fuels-intensive. Emissions from the transport system could grow by 60% by 2050, and transport is the number-one user of oil worldwide. GHG emissions result not only in warming global temperatures, but also in ocean acidification, which has severe consequences for entire ecosystems and further destabilises our climate. The transport system also drives land-use change and biodiversity loss through the development of infrastructure—also releasing harmful pollutants into the ocean. Key circular solutions:

- Embrace and enable car-free lifestyles
- Invest in high-quality public transport
- Rethink unnecessary air travel
- Electrify remaining vehicles

🚌 Mobility Systems

Cities are responsible for 60% of global resource consumption, and with increasing urbanisations, there are growing concerns about forthcoming shortages (water, food, energy). Urban sprawl is costly, damages the environment and affects quality of life. Making cities sustainable will need rethinking of every element of urban living, including the neighbourhood-scale. 

Self-sufficient and socially inclusive neighbourhoods are centralised, self-contained communities, organised in a way that minimises dependency on inputs from outside the system and maximises interaction between its inhabitants. They often produce their own energy and treat their own wastewater, improving security and efficiency of materials, while offering new livelihood opportunities and local value creation.

Local governments can adopt more sustainable and efficient practices in constructing these areas. Through direct and indirect economic incentives, they can push the true costs of infrastructure onto developers and create a favourable real estate climate that helps with empty land in inner-city neighbourhoods. Then, cities can implement circular land planning through urban renewal projects. Building more self-sufficient and circular neighbourhoods will require, however, multi-stakeholder collaborations between municipalities, land developers, construction and waste industries and building owners.

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🏢⚡  Self-sufficient neighbourhoods 

Water system refers to the water supply network for storing and supplying water for use by the community.

One of the greatest challenges of a city is to provide its inhabitants with safe, clean water from a limited fresh water supply. Improving the city’s water infrastructure efficiency, such as minimising leakages, reduces the strain put on the limited supply, which in turn, helps to ensure inhabitants gain access to clean and affordable water.

The water infrastructure of a city typically consists of components such as surface water diversions, wells, pumps, transmission pipes and canals, treatment and storage facilities, and distribution network elements (Burian et al.). Options for improving the efficiency of the system include investing in water loss reduction systems, creating and following a regular maintenance program, and better matching water supply and demand (Global Water Partnership).

Cities can improve the efficiency of their water system infrastructure by conducting a water audit, in which all water flows are traced and losses in the system are identified to map where the most efficiency improvements can be gained. Alongside this, asset management can be used to create a short-term and long-term strategy of investing in new equipment, refurbishing existing equipment and developing maintenance programmes to ensure infrastructure is as efficient as possible, and leaks are minimised. Such management programmes create financial transparency amongst all stakeholders and provide useful long-term planning for larger infrastructure changes (US EPA)

💧 Water Systems

Cycle strategies aim to cycle and reuse materials at their highest value: they maximise the volume of secondary materials re-entering the economy, ultimately minimising the need for virgin material inputs and therefore also narrowing flows. Of course, virgin materials will always be needed to a degree: all materials degrade and can’t be cycled infinitely, use energy, and require blending with virgin materials to maintain strength and functionality.

Cycle

 In the early 1990s, Hammarby Sjöstad had a reputation for being a run-down, polluted and unsafe industrial and residential area. Now, Hammarby Sjöstad is one of Stockholm’s most pleasant residential districts and one of the world’s most successful urban renewal districts.
Hammarby enjoys an excellent location between the rich metropolitan life in the capital and the nature on the periphery of the city.
By 2016, when the second and final phase of the building activities is completed, it will be home to 25,000 people and offer work to another 10,000 people. The attractive mix of apartments, shops, offices and small traders with a focus on culture and entertainment gives Hammarby Sjöstad an inner city atmosphere.
Dagvatten canal © André Vaxelaire
Sustainability
Sustainability was one of the primary areas of focus in the design of this new water-related district. The high sustainability ambitions were integrated into the planning process from the first phases. Sustainable alternatives for managing water, energy and waste were carefully studied at the level of the architecture and infrastructure. For example, all the electricity used comes from renewable sources. New types of fuel cells, solar cells and solar panels are being tested in the area.
The district is the product of a positive collaborative process between municipal authorities, urban planners, developers, architects, landscape architects, engineers at eco-tech businesses, energy company Fortum and the Stockholm Water Company. Traditional forms of urban planning take their inspiration from Stockholm’s 19th century city centre, combined with varied modern architecture. Buildings are oriented toward the sea and the canals, to allow as many houses as possible to profit from the water-rich views. Based on the strategy of a compact green town, a favourable balance has been found between construction and public spaces. The absence of fences and the presence of public spaces with footpaths yield a district with various different atmospheres. The district’s density, which is comparable to that of Stockholm’s city centre, gives it a trendy atmosphere and offers a high quality of life.
Plan © Stockholm City Planning Administration
The energy supplies in Hammarby Sjöstad
The main source of heating in Hammarby Sjöstad, a town within the municipality of Stockholm, is district heating. Thirty-four percent of this heat comes from purified waste water, 47% from combustible household waste and 16% from bio fuel (2002 figures).  When the heat has been extracted from the warm, purified waste water, the remaining cold water can be used for district cooling. This is used in e.g. the cold storage in grocery stores, and also for office buildings as a replacement for energy-guzzling air conditioning systems.
Hammarby Sjöstad is experimenting with different solutions for its energy supply. For example, two buildings with solar cells can be found on the street called Sickla Kanalgata. The solar cells supply part of the electricity needs of the building’s public areas.  One large residential building has been fitted with solar panels. These supply the residents with 50% of the hot tap water they annually use.  Another interesting development project is the fuel cell which has been placed in GlashusEtt, the area’s Environmental Information Centre. The fuel cell could be described as a battery which, instead of being charged, runs on fuel (e.g. hydrogen gas). The fuel cell generates electricity and heat.  Approximately 900 flats in Hammarby Sjöstad now have biogas cookers. The biogas comes from the residents themselves. It is formed when sludge from the waste water treatment is digested. Amazingly, the amount of biogas “produced” by the average family is close to that which they use for cooking. By replacing electric cookers with ones that run on biogas, the electricity consumption has been lowered by 20% in the buildings in question.
 © Jonathan Perrin / Malena Karlsson
Energy goals
The town’s current environmental goals, listed below, refer to the annual sum of all energy purchased to heat and operate its public buildings. Household electricity is not included.

District heating connection with exhaust air systems: 100, of which 20 kWh electricity/m2 UFA.
District heating connection with heat extraction systems: 80, of which 25 kWh electricity/m2 UFA.
The entire heating supply shall be based on waste energy or renewable energy sources.
Electricity shall be “Good Environmental Choice”- labelled, or equivalent. [Hammarby Sjöstad, 2012]

Integral energy, waste and water system © Bumpling AB
Water
The first step in the sustainable water management is a proper participation and education model for the district’s residents. Proper education and use of water-saving appliances will reduce the amount of drinking water consumed by 50%. Water consumption levels of 200 litres per person per day are normal in Stockholm. As such, the focus of the education and participation strategy is on reducing pollutants in wastewater by 50%, by raising residents’ awareness of the impact of detergents and other household activities.
The residents of Hammarby have the option of monitoring their energy and water consumption via the internet to increase their awareness of their habits.
 © Madeleine d'Ersu
Glashusett
An environmental centre called GlashusEtt has been realised in the district to provide locals with information and education about all aspects of sustainable urban planning and to encourage the residents to adopt a more sustainable lifestyle. [GlashusEtt, 2007]
Wastewater
Wastewater is treated locally. The sludge produced by the treatment process is recycled and used for fertilising farmland and forestry land. The waste releases biogas during processing. That biogas is used as fuel for vehicles such as buses, taxis and waste collection trucks, and to heat 1000 homes in the area.
Heat is extracted from the treated water in the treatment plant, which is then used for district heating. With a spread in temperatures ranging between 10°C and 20°C over the whole year, the wastewater is highly suitable for both heat and cold extraction. In summer the cold water can be used for cooling.
 © Malena Karlsson / Jonathan Perrin
 © Jonathan Perrin / Madeleine d’Ersu
Rainwater
Rainwater infiltrates the ground directly or is drained off through canals. The many small canals are part of the design of the urban landscape. Some of the roofs have been designed as green roofs that buffer much of the rainwater.
Runoff from roads is captured separately and drained off to treatment pools before being allowed to infiltrate the ground.
The Hammarby model shows that wastewater can be used in multiple different ways and that rainwater can be returned to the natural cycle. Hammarby has become an example of sustainable urban planning. For example, it inspired Toronto’s Waterfront (Canada), London’s New Wembley and many cities in China and Thailand. [World Clean Energy Awards, 2007; P-A Malmqvist, 2006] 

The Hammarby Sjöstad district in Stockholm was designed around the closed-loop metabolism concept, which embraces synergies among water, energy, and transportation services. The district is heated by purified waste water, combustion of household waste and biofuel; once heat has been extracted from waste water, it is used for cooling. The biogas produced is used to run local transit.