Paul Hans Brunner

The aim of this paper is to show how an “Urban Metabolism” approach can be used for analysing, designing, and optimizing material and energy flows and stocks in human settlements. For this purpose, material flow analysis (MFA) and substance flow analysis (SFA) is applied in a rigid way to quantitatively model metabolic processes such as supply and disposal of goods in a city. The characteristics of relevant material flows and stocks of urban areas in space and time are examined. Results of two metabolic case studies on resources, waste management, and environmental protection are presented. By introducing the so called “Activity” concept, it is shown how the Urban Metabolism approach is instrumental for the design of sustainable anthropogenic systems. Finally, it is suggested to use the methodology for technology assessments and the optimization of entire anthropogenic systems.

This mini-review aims at proving that waste-to-energy (WtE) is an essential cornerstone for circular economy (CE). Based on literature, the history of thermal waste treatment over the last 150 years is investigated, from open burning to WtE with resource recovery and final sink function. The results show that in the past incineration solved the issues it was designed for but often created new and sometimes even worse problems: The introduction of incineration in the 19th century improved urban sanitation, decreased waste volume and prolonged operational life of landfills. But it also polluted the environment, triggering an unprecedented scientific and engineering effort of all stakeholders. Today, WtE is one of the best investigated and optimized technologies in waste management. It enables the recovery of energy as heat and electric power and facilitates the ‘cleaning’ of cycles by the destruction of hazardous organic substances. Recent developments in resource recovery from WtE residues allow to recycle metals and, in the case of sewage sludge, even phosphorus by thermal recycling. Combined with carbon capture and storage technology, WtE stands for a quantifiable contribution to greenhouse gas reduction. Today, WtE is indispensable to reach the goals of CE, namely recycling of energy and materials, supplying safe final sinks for persistent organic substances and minimizing the need for sinks for hazardous inorganic substances.

The rationale for this article is that often, decision-makers in waste management (wm) tend to neglect goals and confuse them with means like circular economy or waste hierarchy. Because clear goals are crucial for developing effective wm strategies, the objectives of this mini review are (1) to clarify wm goals in a historical context by a literature review, (2) to investigate how (a) these goals have been observed in general scientific publishing and (b) specifically in Waste Management and Research ( WM&R) and (3) to recommend measures for better consideration of wm goals by the publication sector. Based on general as well as specific bibliographic analyses of databases in Scopus and Google Scholar, the study confirms that little attention was given to wm goals in scientific publishing. For instance, during the first 40 years of WM&R, 63 publications and eight editorials were found containing terms related to wm goals, but only 14 respectively and eight explicitly discuss wm goals. We recommend focussing more on wm goals. Editors, authors, reviewers and professional associations in the field of wm should become aware of this challenge and react. If WM&R decides to become a strong platform for the issue wm goals, it will be in a unique selling proposition and more authors, articles and readers are likely to result. This article aims at setting a starting signal for such an endeavour.

Summary: This article reviews, categorizes, and evaluates the objectives, means, and results of the application of material flow analysis (MFA) in waste management. It identifies those areas where MFA methodologies are most successful in supporting waste management decisions. The focus of this review is on the distinction between MFA on the level of goods and on the level of substances. Based on 83 reviewed studies, potentials, strengths, and weaknesses are investigated for the two levels of MFA when applied for analysis, evaluation, and improvement of waste management systems. The differences are discussed in view of effectiveness, applicability, and data availability. The results show that MFA on the level of goods are instrumental for understanding how waste management systems function, facilitating the connections of stakeholders, authorities, and waste management companies. The substance level is essential to assess qualitative aspects regarding resources and environment. Knowledge about the transformation, transport, and storage of valuable and hazardous substances forms the base for identifying both resource potentials and risks for human health and the environment. The results of this review encourage the application of MFA on both levels of goods and substances for decision making in waste management. Because of the mass balance principle, this combination has proven to be a powerful tool for comprehensively assessing if a chosen system reaches designated waste management goals.