SECTOR WATCH 

Innovation and Resources on Urban Waste

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Analysis

Modelling the Urban Metabolism for Circular Cities

22 February 2019

Becoming Circular is an important goal for cities worldwide. And it is promising. A circular economy could put an end to resource exploitation without halting global production.

But to get to that place, a deep understanding of current resource flows is necessary. Traceable data about most material stocks and flows is still scarce. This limits policy makers’ leverage to design new policies and hinders industry from reusing materials efficiently.

The UrbanWINS project sees cities as living organisms that eat, digest, and dispose of materials. It seeks to understand the process whereby resources enter, stay, and leave the system.

A key tool to reach this level of understanding is the Urban Metabolism Analyst (UMAn) model. It is a method of material flow accounting that allows decision makers to investigate the relationship between the economy, policies, lifestyles, and flows of resources. It helps to implement more efficient and targeted waste management and prevention tools – eventually transitioning to an advanced circular economy.

For this edition of Sector Watch, we have spoken to researcher Leonardo Rosado of Chalmers University (Gothenburg, Sweden) about the potential of analysing material flows on a city and regional level.

The UMAn model is a powerful tool to support cities and regions in the transition towards a circular economy. It is a holistic model of material stocks and flows that accounts for all product and material categories that enter, stay, and leave the urban system. Its power lays in the comprehensiveness that this overview provides to decision makers.

The model combines analysis of stocks and flows. The flow analysis provides insight into material consumption over time, which allows for comparisons and shows trends in material consumption. The stocks analysis shows which materials remain in the urban system – accumulating and eventually becoming so called waste in the future.

The UMAn model is about more than just waste. It addresses the broader topic of material consumption and therefore allows for active interventions rather than reactive waste management.

This can be achieved by modelling various future scenarios, which show the impacts of different waste management and prevention policies. Combined with environmental impact data on the materials that are tracked in the model, it can reveal hotspots in the environmental impacts of a city, identifying the most problematic product categories.

Results

As part of the UrbanWINS project, the UMAn model is used to research material stocks and flows of several cities. The results point to priority areas for intervention in the region. The analysis of the material flows in for instance the city of Leiria has successfully identified the top product groups and materials in circulation in the city.

Agricultural products such as straws and husks, maize and corn produced in the livestock industry and construction materials are among the biggest consumed products. These product types offer circular opportunities. By-products from straws and husks can be used to improve the nutrient level of the soil. Waste biomass can be converted to energy using the maize waste, and sands and other building materials can be used for new construction works. The City of Zurich is an inspiring example of how the construction and demolition waste can be used in new building material.

Challenges ahead

The UMAn model is designed to account for every conceivable product, which is a strength and a weakness since often the required data is either not available or it is confidential.

The fact that the model examines at the city level is another two sided coin: it allows for precise insight on the one hand, but on the other, the boundaries of a city are not as clear cut, and often it is more useful to look at regions.

Analysing the resource flow of a city with the UMAn model is just a starting point. The results need to be translated into solutions, such as sustainable procurement or urban planning tools and the model in turn can be applied to evaluate their success.

To learn more about the UMAn model and how you can apply it on your city join us at the UrbanWINS final conference in Brussels on April 4, 2019. For more information on this full day conference dedicated to the urban metabolism and local action for a circular economy click here.