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Urban Refinery – make use of the waste

Energy recovery from waste is well developed in Sweden and waste currently accounts for about 25% of district heating production, where efficient plants and good demand for heat have led to a favorable cost picture for waste incineration.

According to the EU's waste hierarchy, waste prevention, recycling, recycling and biological recovery must be given priority over energy recovery. The vision is to achieve a more circular system where resources are reused. Despite the fact that Sweden is far ahead in terms of material and energy recycling, much remains to be done to achieve this vision. More efficient and sustainable use of waste (waste as a resource) is highlighted as a priority in the proposal for a new national waste plan.

This project focuses on how existing waste treatment infrastructure can be used more efficiently than today. New forms of collaboration between thermal and biological waste treatment could enable the production of new products from wastes, reduced use of primary resources, increased energy efficiency and improved waste management economies, thus contributing to resource-efficient communities and more sustainable energy systems.

The project combines technical and social science research on the waste system as a sociotechnical system. Analysis of new process integration concepts and raw material exchanges based on their energy, resource, environmental and economic performance is matched by social science research from actor, market and decision-making perspectives, with a focus on opportunities for, and obstacles to, actual implementation of innovative waste treatment concepts. The project has a strong focus on actors and customers.

Purpose

This interdisciplinary doctoral project has two overall purposes:

  • to improve the use of existing waste treatment systems and infrastructure, in order to contribute to more resource-efficient societies and more sustainable energy systems, and
  • to contribute to the supply of skills and the development of energy system research in Sweden.

Goal

The project's goal is to increase knowledge about opportunities for and obstacles to using waste management infrastructure for the production of energy carriers and energy-intensive products from existing and future waste flows, in particular with a focus on sewage sludge.

Project results

The project "Urban Refinery – Making use of the useless" was carried out within the Research School in Energy Systems (FoES18), funded by the Swedish Energy Agency. Its aim was to integrate biological and thermal treatment processes for waste to create a more resource-efficient and sustainable energy system. This was explored through three doctoral projects at Luleå University of Technology (LTU) and Linköping University (LiU). A reference group from various sectors provided crucial perspectives.

The project investigated how to enhance energy recovery and resource utilization by combining biological and thermal treatment of organic waste. The goal was to develop new concepts and management chains, assess their effectiveness, and identify barriers to implementation. The project's greatest anticipated benefit is the development of interdisciplinary research expertise in energy systems, which will be disseminated into society through the graduates it produces.

The three doctoral projects were:

  1. Torben Bauer (LTU Waste Science and Technology): Investigated interdisci-plinary challenges in wastewater sludge management and proposed sustainability improvements.
  2. Marzieh Bagheri (LTU Energy Engineering): Conducted techno-economic analyses of treatment scenarios for wastewater sludge and identified economic conditions and barriers.
  3. Linus Ekman Burgman (LiU Theme Technology and Social Change): Ana-lyzed the historical management of wastewater sludge and its utilization.

Key findings are that (i) Effective wastewater sludge management requires com-bined technical, economic, and social solutions; (ii) Updated legislation and im-proved collaboration between stakeholders are necessary to overcome current challenges; and (iii)
Integration of biological and thermal methods can recover valuable resources.

Innovative methods explored include (a) Hydrothermal Carbonization (HTC); it improves dewatering, reduces energy needs, and enables phosphorus recovery but is economically challenging due to high initial costs; (b) Addition of Ash to the digestion chamber; it shortens biological treatment from 15–20 days to four days and extracts gas more efficiently, particularly beneficial for smaller communities; and (c) Combination of biological and thermal treatment processes to optimize energy recovery and resource extraction, particularly phosphorus and potassium.

The project's results were reported in scientific publications and presented at conferences, workshops, and stakeholder meetings. Four overarching conclusions summarize both published results and meta-findings based on combined insights:

  • Outdated laws and uncertainty hinder progress in sludge management.
  • HTC and ash treatment offer potential but require economic and technical ad-justments.
  • Research focus has shifted from disposal to resource recovery, but there are gaps in economic feasibility and implementation of new technology.
  • Comprehensive strategies are needed for sustainable sludge management solutions.

Read Final Report here

Publications

Marzieh Bagheri, Torben Bauer, Linus Ekman Burgman, Elisabeth Wetterlund. (2023) Fifty years of sewage sludge management research: Mapping researchers' motivations and concerns, Journal of Environmental Management, Volume 325, Part A, 2023, 116412, ISSN 0301-4797, https://doi.org/10.1016/j.jenvman.2022.116412.

Bagheri, M.; Öhman, M.; Wetterlund, E. Techno-Economic Analysis of Scenarios on Energy and Phosphorus Recovery from Mono- and Co-Combustion of Municipal Sewage Sludge. Sustainability2022, 14, 2603. https://doi.org/10.3390/su14052603

Linus Ekman Burgman, Björn Wallsten, (2021). Should the Sludge Hit the Farm? – How Chemo-Social Relations Affect Policy Efforts to Circulate Phosphorus in Sweden,
Sustainable Production and Consumption, Volume 27, Pages 1488-1497, ISSN 2352-5509, https://doi.org/10.1016/j.spc.2021.03.011.

Torben Bauer, Linus Ekman, Lale Andreas, Anders Lagerkvist (2020). Effects of the Different Implementation of Legislation Relating to Sewage Sludge Disposal in the EU Detritus, Vol. 10 , s. 92-99 https://doi.org/10.31025/2611-4135/2020.13944

People in the project

Research leader

Lale Andreas, Senior Associate Professor, Luleå University of Technology

Project participants

  • Harald Rohracher, Professor, LiU
  • Anders Lagerkvist, Senior Professor, Luleå University of Technology
  • Marzieh Bagheri (has defended her thesis)
  • Torben Bauer (has defended his thesis)
  • Linus Ekman Burgman, post doc, LiU

Project partners

  • Luleå University of Technology
  • Linköping University

Read more about FoES

Energy is everywhere, sunset.

Graduate School in Energy Systems

Graduate School in Energy Systems purpose is to increase understanding of how energy system depends on the interaction between technology and society's regulatory framework, policy development and operators interests and behavior.

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