This PhD thesis focuses on multidisciplinary challenges in sewage sludge management and how they can be addressed to increase sustainability. 

Sewage sludge is the residual from wastewater treatment. It contains both resources and contaminants making its management challenging. In the past sewage sludge was often used as a fertilizer in agriculture, a practice that is still used in several countries. Today, this practice gets questioned in Europe and especially in Sweden due to the presence of contaminants in the sludge. At the same time, the resources in the sludge get into a stronger focus as society moves towards a circular economy and food production should get more resilient in a world with geopolitical challenges. In sustainable sewage sludge management, the two goals of immobilising/destroying the contaminants and utilizing the resources in the sludge are combined. 

This thesis identifies challenges in various disciplines and provides potential solutions to make sewage sludge management more sustainable. The discussed challenges cover the following areas: legislation (EU and Sweden), perception of sewage sludge (Sweden), research on sewage sludge management (international), and combinations of treatment methods. Results show that outdated legislation in Sweden creates insecurities, while the negative perception of sewage sludge in Swedish society further aggravates these insecurities. Although technical solutions are available or under development, e.g., treatment combinations that can separate resources and contaminants, actors in Sweden remain hesitant due to the aforementioned insecurities. This thesis emphasizes that interdisciplinary approaches, and dialogues between different actor groups and society are essential. The multitude of challenges requires solutions that combine technical and non-technical approaches. Therefore, this thesis provides recommendations for more sustainable sewage sludge management practices, including updating legislation.

Generation of waste is unavoidable. While human use of natural resources, at least initially, is often about refining resources, it typically also involves a reduction in value in the form of, for example, losses of energy or gradual deterioration of physical objects. The use of resources thus contributes to the production of waste. Waste is considered a nuisance and has historically been dealt with in the cheapest, or easiest way possible. Current resource use and consumption rates are, however, often considered unstainable, and according to some estimations humanity is currently consuming about three plantes worth of resources. Circular economy, where generation of waste is minimized, and reutilization of waste is increased, has therefore been proposed as an economic model for the future. One, frequently mentioned, barrier towards circular economy is the legal system. When it comes to new and innovative practices, legal systems often adapt at slow pace. This is also the case for European waste law. Waste is within the European Union (EU) regulated through the 2008 Waste Framework Directive, which is a minimum directive. Waste law is an area where the EU exercises great influence over Member State (MS) policy and MS may not implement laws that provide for a lower level of protection than what EU law mandates. As is often the case in studies related to environmental law, the legal system in focus for this study is EU environmental law, as a large part of the national regulations are either influenced by or derived from EU law as a large share of national provisions are either affected by, or stem from EU law (or both).

The aim of this dissertation is to examine the role of law in relation to both environmental protection in the immediate sense, and reutilization of waste. Previous research has established that waste law can be said to have developed around how waste is defined legally, and that the definition of waste is a cornerstone of the entire corpus of waste law as it determines what can and cannot be controlled by the substantive rules the framework provides. To this end, the dissertation examines the relationship between key terms for the applicability of the WFD, the concepts of waste, by-product and end-of-waste through legal analysis. It builds on previous research by assessing the coherency between these terms. Special attention is paid to under what circumstances a substance or object may transform into a waste and vice versa. The dissertation shows that transformation from non-waste to waste, and waste to non-waste differ. the law sets higher requirements for something to be classified as non-waste than for the object to be classified as waste, as a result of the mandatory, cumulative, conditions that must be fulfilled for end-of-waste and by-products. This means that substances or objects are included in and excluded from the protective governance of waste law on different terms. In this regard, the dissertation suggests that this incoherency can be alleviated by the alignment of the concepts of waste, by-product and end-of-waste.

In addition, the dissertation also examines the regulatory framework for two specific waste streams: legacy waste and sewage sludge. Sewage sludge is, through the Sewage Sludge Directive (SSD), regulated lex specialis. Here, the perceived appropriateness of the regulatory framework is examined through interviews with sector stakeholders. A key finding is that the regulatory framework is perceived to be obsolete by the stakeholders, an opinion that is mirrored in literature, but also that it is possible to enforce stricter requirements than what is called for by the SSD. This highlights a gap between ‘law in books and law in action’. Regarding the recovery of legacy waste, the dissertation shows that, chiefly, the regulatory framework is not designed for recovery of such waste. This result mirrors previous literature showing that the current regulatory framework is not designed for the objectives of circular economy, such as recovery of legacy waste. For instance, specific provisions are missing for both the recovery of mining waste and landfill mining. The regulatory framework can thus, in this regard, be considered as underdeveloped, which means uncertainty for the actors involved.