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Published: 2021-06-30

New evaluation model for more sustainable cities

NEWS Kavitha Shanmugam proposes a model for assessing urban sustainability. The model framework, which combines two different life cycle tools, takes into account the combined effect of the city's central services in water, waste and energy and aims to increase the degree of circularity. Kavitha defended her dissertation on Monday 10 May at Umeå University.

Text: Ingrid Söderbergh

“The purpose of this system-oriented tool is to help cities develop strategies for sustainable urbanization, monitor progress and reduce the environmental impact caused by, for example, municipal wastewater treatment plants, energy plants and biogas plants for organic food waste. The framework enables comparisons between cities, based on how environmentally friendly the most important services are run in each city and to what extent they contribute to a city's sustainable results,” says Kavitha Shanmugam, doctoral student at the Department of Chemistry at Umeå University.

By 2050, it is estimated that more than two thirds of the world's population will live in urban areas. This urbanization puts enormous pressure on our cities. Among other things, the cities are responsible for providing three important municipal services to the inhabitants, namely water supply, wastewater treatment and the management of various forms of solid waste generated by the inhabitants. Ensuring the sustainability of these important services is becoming increasingly difficult for cities with a growing population.

It is therefore of great scientific and societal value to develop methods that make an assessment of cities' current and possible future metabolism with the aim of achieving increased circularity within central service activities.
Kavitha Shanmugam has developed an assessment method based on applications of life cycle assessment (LCA) and life cycle costing tool (LCC) designed to describe the degree of sustainability of the three important municipal services.

“The integrated model that I propose in my dissertation is potentially more useful for cities to develop strategies and make decisions related to sustainable urbanization, with a focus on water, waste and energy,” says Kavitha Shanmugam.

Data used for the modeling were obtained from the Umeå municipal companies VAKIN, Umeå Energi and Dåva DAC and the Skellefteå Biogas Plant. The assessment of the main services (wastewater and solid waste) can be applied using the method to cities with a similar population of around 130,000 inhabitants, which is also comparable to most European medium-sized cities with similar technology practices.

The model framework can serve as a basis for developing a decision support system that cities can use to iteratively evaluate and improve their sustainability performance. The proposed framework discusses in detail the needs for data, steps and technical alternatives that may be possible in waste and water treatment services. In addition to the environmental impact of the services, external costs related to the effects of the business can also provide a better perspective for stakeholders.

The work in the dissertation is a contribution to answering questions about alternative use of waste by-products, future scenarios for waste management and wastewater management in cities and to understand their contribution to the city's total demand (energy, fuel, materials). Kavitha Shanmugam has made an assessment of the degree of circularity of sewage treatment plants in cities based on the operation and use of by-products, including private and environmental external costs.

She also analyzes the social cost benefits of using biogas from the treatment of organic food waste as fuel for public buses. The effects of using fly ash as part of new materials were also seen as an alternative to valuable resource utilization to avoid fossil sources. The different specific cases of modeling for different treatment services have paved the way for identifying a more integrated assessment framework that can be further developed into a decision support tool.

The work has been carried out within Grön teknik och miljöekonomi, a research and collaboration platform for resource efficiency and circular economy in a collaboration between Umeå University and Umeå municipal companies Umeå Energi, Dåva DAC and VAKIN. The dissertation supports and is most relevant to the global sustainability goals SDG 11: Sustainable cities and communities and SDG 6: Clean water and sanitation for all.

Read the whole thesis