In June 2012 at the Rio +20 global summit on sustainable development, UN Environment launched the Global Initiative for Resource Efficient Cities (GI-REC) to capitalize on the potential for cities to lead action towards greater resource efficiency. One of the initiative’s core activities is to help cities develop and use a systemic approach such as urban metabolism for evidence based decision-making processes.
Urban metabolism is a framework for modeling urban systems’ flows — water, energy, food, people, et cetera — as if the city was an ecosystem. It can be used to analyze how urban areas function with regard to resource use and underlying infrastructures, and helps us understand the relationship between human activities and the natural environment.
However, as highlighted in GI-REC’s 2017 report to capitalize on the potential of cities to lead a global shift toward resource efficiency, the practical implementation of the concept of urban metabolism in spatial planning and policy development has as of yet been limited, due in part to a lack of standardization of methods and minimal guidelines for how to shape a sustainable urban metabolism.
To translate the urban metabolism concept from theory to making practical interventions that can change resource consumption behavior and waste generation, the authors offer insights and recommendations that include:
- The need to undertake a basic urban metabolism assessment for all cities, which will ensure comparison for all cities, in both developed and developing countries
- Moving from top-down to bottom-up approaches in order to capture data unavailable in conventional databases
- Linking spatial and temporal issues in urban metabolism assessments
- Switching between the different scales of analysis, for both urban metabolism assessment and spatial planning
- Promoting a transdisciplinary approach, in which co-design takes place with society, and not for society, and to ensure assessment is not a once-off event
- Promoting system dynamics modelling to examine the complex, dynamic interrelationships that exist in physical and social processes of the urban metabolism and their implication for urban planning and design intervention
In order to apply and scale these urban metabolism approaches on-the-ground, GI-REC has been building on its existing networks to partner with cities and organizations who are successfully utilizing urban metabolism approaches to guide urban design and infrastructure decisions and implement solutions that create economically and socially healthier, more efficient and less wasteful cities and neighborhoods.
Realizing the need and demand for real life examples presented in accessible formats if these invaluable tools and methods are to be utilized by a growing number of diverse stakeholders, GI-REC launched a blog/vlog series to profile existing applications of urban metabolism and its utility in city planning and management while shifting resource flows from linear toward circular. These educational posts and videos, produced by Ecocity Builders in coordination with the Sustainability Institute,urban Modelling and Metabolism Assessment, and Metabolism of Cities, are meant to equip city managers and practitioners with the tools and know-how to build and transition towards low-carbon, resilient, and resource efficient cities using integrated systems approaches such as urban metabolism.
The following case studies showcase some of the current leading cities in the field, highlighting their efforts, successes, as well as challenges in using urban metabolism techniques to transform their urban environments into more resilient and wholesome organisms.
Brussels: Transitioning towards a more circular economy
With its resource flows through the urban system lacking much reuse, recycling, or other diversions and loops, a commonsense approach for Brussels to address the conditions at the core of this linear urban metabolism was to tie the region’s mitigation and reduction of its ecological footprint into a broader circular economy context. Convinced that an economic framework outside of the predominant modern industrial cradle-to-grave model must be at the core of balancing the need for a healthier urban environment and the creation of new jobs, the Brussels Capital Region (CPR) adopted a Circular Economy Plan.
One of the co-authors of the study, Aristide Athanassiadis, talks about the importance of urban metabolism as one of the centerpieces of making a city’s economy more circular, as it goes beyond simply tracking flows. “Measuring the entering and exiting flows is not enough,” the co-founder of Metabolism of Cities and Chair of Circular Economy and Urban Metabolism at Université Libre de Bruxelles contends. “You need to understand the systems of your city much more in-depth than that. You need to understand who is consuming, where we are consuming, why we are consuming, and what the drivers are behind the consumption. Therefore urban metabolism really adds a systemic understanding to the flows.”
What makes Brussels such a good candidate for in-depth urban metabolism analysis and visualization is the availability of good data on both the regional and local scale. Its statistical office, the Brussels Institute for Statistics and Analysis, collects and provides data at regional, municipal, and even smaller scales, providing insights into important socioeconomic, territorial, and environmental aspects of its urban systems. While data for what type of materials enter or leave the region is harder to come by than for water or energy, the Metabolism of the Brussels Capital Region study shows that a detailed analysis of material flows is quite feasible with the proper amount of research and innovative thinking.
Cape Town: Applying a metabolic lens to a water crisis
With its extreme water shortage gaining worldwide attention in recent months, Cape Town’s case study serves as a living testament to the difficulty in planning for and managing resources as well as responding to crisis and how urban metabolism can serve as an important tool to locate linear flows and shift towards more circular ones.
Researchers Paul K. Currie and Paul Hoekman point out that conceptualizing Cape Town’s metabolism allows them to understand how many resources the city is taking from its surrounding areas, digesting them for economic production and social welfare, and then dumping the wastes back into the environment. In the case of its most voluminous resource — water, an urban metabolism analysis shows just how its mono source makes the city and its residents vulnerable to extreme shocks to the system like the current one: Cape Town receives 97 per cent of its water from surface runoff in the Berg River catchment, most of it stored in six large dams and pumped in bulk to the city’s 12 water treatment works.
By identifying resource flows that can be reused or processed in different ways, the authors point out that the city’s metabolism can be made more effective, reduce the reliance on fresh resources, and reduce the impact of wastes. Aside from undertaking emergency water source diversification that aims to bring 300 million liters of desalination capacity, 100 million liters of groundwater and 100 million liters of retreated effluent into the water system, the city has already effectively reduced the its daily water demand by more than half through behavioral interventions such as widespread messaging, increased step tariffs, or network repairs.
Unpacking its water metabolism has allowed for greater insight into Cape Town’s water requirements. Experts such as GreenCape’s Water Programme Manager Claire Pengelly and the African Climate & Development Initiative’s Research Chair Martine Visser agree that connecting supply and demand and looking at the full life-cycle of water within the city at both household and city-wide levels has led to a deeper understanding that supports better decision making around Cape Town’s water metabolism.
Cusco: A participatory approach to urban metabolism
The next case study brought an increased focus on “moving from top-down to bottom-up approaches in order to capture data unavailable in conventional databases” and “promoting a transdisciplinary approach, in which co-design takes place with society, and not for society, and to ensure assessment is not a once-off event.”
Focused on the metropolitan area in and around the city of Cusco in southern Peru, Secondary Cities is partnering with their on-the-ground implementation team, Ecocity Builders, to engage in a multi-faceted and multiple phase participatory action approach to urban environmental accounting that includes a collaborative deliberation process between local citizens, city officials, and student researchers from the local university. The city’s historic inner city neighborhoods, where several small study areas are located, have increasingly been feeling the need for this kind of in-depth accounting of conditions on the ground that is required to institute a holistic solution to their garbage problem.
Facilitated through the EcoCompass workshops of Ecocity Builders’ Urbinsight Global Data Initiative, participants that include faculty, students, local officials, architects, and planners were introduced to the technical, community engagement, and planning processes essential to participatory action research, learning the ins and outs of creating a dynamic mapping platform that visualizes multiple data types. With citizen engagement at the core of the process, community members were an integral part of the research. Through scoping sessions and roundtables, they communicated the changes they wanted to see in their city: better management of waste, a cleaner environment, and healthier food.
Based on these needs, student teams conducted neighborhood material audits and collected consumption and waste data from residents, who participated by sorting their solid waste, weighing materials by type, and analyzing composites. The team created detailed views of neighborhood archetypes of the historic districts, which gave important insights into solutions for neighborhoods with similar characteristics and challenges. Based on their findings that 50% of household waste is organic, they researched and co-designed with community members compost modules that were piloted throughout four communities in the homes of participating neighbors.
The graphic tools used to visualize the data collected into neighborhood metabolism diagrams have become conversation pieces that help the community as well as city planners make informed decisions about how to redirect the flows from linear to circular. Community members found that in order to understand urban metabolism it is necessary to understand the origin of resource flows, their distribution within the city, and how the resources are being used. These insights empower people to create informed change in their unique urban contexts, which is currently being enshrined in the city’s DNA as part of the project’s next phase through the creation of the creation of Neighborhood Sustainability Plans.
Medellín: Co-creating more robust urban knowledge systems
In February 2013, the Urban Land Institute chose Medellín as the most innovative city in the world due to its advances in politics, education, and social development. Although Medellín has been crowned Most Innovative City, boasts very wealthy neighborhoods and sets an example for urban planning to the world at large, the city is still challenged by harsh economic disparity. Wealth mainly clusters around the city center and decreases exponentially into the surrounding hills.
In Phase I of another Ecocity Builders/Secondary Cities project, local planners, utilities, academics, and local non-profits teamed with community members of Comuna 8, one such vulnerable hillside district outside of the city center that is made up of several low income formal and informal neighborhoods, to apply local participation methods to urban metabolism. The 2C/Medellín team focused their data collection and mapping on waste management, material flows to and through households, and citizen perspectives of waste practices in their communities throughout several neighborhoods within Comuna 8, a priority expressed specifically by community leaders.
After they collected the data, participants were able to apply their training from the workshops by using Urbinsight’s metaflow app to turn their collective data input into urban metabolic information system flow diagrams. These visualizations proved not only important for researchers to streamline and interpret the household and parcel scale data, but for Comuna 8 residents to understand and improve their own waste stream and for the city to understand the needs of its people.
For Phase II of the project, the 2C/Medellín team determined that the next priority neighborhood type should be a mixed income city center neighborhood. Many neighborhoods of this type are situated within the city center amongst more wealthy business districts, but are overlooked by the municipality. As a result, community members of these neighborhoods often have lower earnings, high unemployment, reduced waste collection services, reduced security or health services, and increased air pollution.
On recommendation by the planning department, University of EAFIT took the lead as the main academic partner, which suggested Boston, a neighborhood characterized as the intended archetype (mixed-income, city center), as the recommended study area. Low Carbon City(LCC), a Medellín-based and internationally recognized non-profit organization with strong ties to the Boston community, joined as the community based partner.
After the data collection activities, participants divided into research teams based on categories of materials that were found to be the most common in the waste stream: plastic, glass, metal, paper, organic, hazardous waste and oils, and mixed waste. Using the field data, they produced reports and presentations on actions that citizens can take to reduce demand, increase efficiency, and reuse/repurpose and recycle materials at home and in the neighborhood in order to decrease waste issues and hazards in public spaces.
During two mapathons participants completed data georeferencing and analysis on their waste and materials audits and geoprocessed original data to develop geospatial layers for further analysis and map development. They then worked with the team to integrate municipal data layers with the original data layers to produce original maps that they presented to the community members. In a final community event, each group presented interactive participatory educational activities relating to their type of resource topic. They developed posters and short videos to “tell the story” of materials and urban metabolism and the role citizens play in resource cycles.
Since their collaboration in 2017, the course participants and Low Carbon City have maintained a strong connection to the planning office, which has been analyzing all course data to be officially recognized by the municipality and included in their open data portal for planning and analysis. Intrigued by the potential use of the Urban Metabolism assessment methodology, Planning Department professionals asked to collaborate with the 2C team on a city-wide data collection exercise to complete all available UM studies.
The project has now entered its next phase during which the partners are once again coming together to create a Sustainable Neighborhood Plan. Building from initial and ongoing urban metabolism assessments, methods and participatory processes, the plan is meant to be adaptable and replicable and is based on Ecocity Builders’ bottom up approach to ecocity development, underscored by urban metabolic information systems (UMIS) assessments at the neighborhood scale.
More sustainable and resilient urban futures can be furthered by using urban metabolism studies and approaches in an ongoing and iterative process. Healthy urban metabolism, just like a healthy ecosystem or an organism, works best when it’s frequently monitored and continuously fine-tuned. Finally, since human beings are essentially driving the demand for resources that shape a city’s metabolism, it is imperative that citizens are allowed participate in a meaningful way.