Upscaling biowaste valorization
A crucial component towards sustainable bioeconomies
Time: Thu 2025-08-21 13.00
Location: F3, Lindstedtvägen 26-28
Language: English
Subject area: Energy Technology
Doctoral student: Eftychia Ntostoglou , Energisystem
Opponent: Professor Teis Hansen, University of Copenhagen
Supervisor: Professor Viktoria Martin, Energiteknik; Docent Dilip Khatiwada, Energisystem; Professor Semida Silveira, Energiteknik
Abstract
The importance of developing sustainable waste management systems has been globally recognised. As biowaste is the largest fraction of municipal solid waste, it has a crucial role in achieving this objective and relevant policy targets such as the Global Methane Pledge.
In this context, it is essential to valorize unavoidable biowaste to circulate its resource value. Various scientific studies have addressed the technical, economic and environmental aspects of biowaste valorization (BV). However, its socio-technical aspects, which are equally important, have received limited attention so far. This thesis aims to contribute to filling this research gap by addressing the socio-technical aspects of BV and how they influence its upscaling from niche applications to mainstream implementation. More specifically, this thesis aims to provide socio-technical insights on the potential sustainability implications of BV, the practices that can support its upscaling and the lock-ins and path-dependencies involved. It uses a mixed-methods approach and draws data from the scientific literature as well as empirical data from Greece and Sweden, as cases at different phases in their BV transition.
Paper I provides insights into the potential sustainability implications of upscaling BV. Paper II addresses decentralized anaerobic digestion as a BV practice and shows key knowledge gaps and themes for future research and development. Paper III investigates BV development and highlights the need to support both mature and radical innovations to support the adaptive capacity and long-term sustainability of BV systems. Paper IV provides insights into the integration of biowaste as a feedstock in biorefineries to contribute to sustainable BV and bioeconomy systems.
A major contribution of this thesis is that it synthesises evidence on three types of lock-ins that can occur at different phases of the BV transition. I illustrate the challenges to escape the carbon lock-in in the BV context but also show how BV systems can get locked-in to specific treatment technologies (e.g. anaerobic digestion) which can compromise the systems’ adaptive capacity. Moreover, I highlight a potential ‘consumption lock-in’: the risk of upscaling BV at the expense of efforts towards biowaste prevention and redistribution. These three types of lock-ins can lead to path-dependent BV systems and compromise their long-term sustainability.
The thesis findings also highlight the need to address biowaste management in the wider bioeconomy context to unlock synergies with other bioresources and address trade-offs. This requires interdisciplinary and transdisciplinary collaboration among different actors involved in the bioeconomy. However, the findings suggest that such actors still largely operate in silos. The thesis provides insights for researchers and other stakeholders involved in biowaste management and the bioeconomy towards the implementation of sustainable biowaste valorization that addresses context-dependencies.