Melanie Haupt

Precious metals and rare earth elements in municipal solid waste--sources and fate in a Swiss incineration plant.

In Switzerland many kinds of waste, e.g. paper, metals, electrical and electronic equipment are separately collected and recycled to a large extent. The residual amount of municipal solid waste (MSW) has to be thermally treated before final disposal. Efforts to recover valuable metals from incineration residues have recently increased. However, the resource potential of critical elements in the waste input (sources) and their partitioning into recyclable fractions and residues (fate) is unknown. Therefore, a substance flow analysis (SFA) for 31 elements including precious metals (Au, Ag), platinum metal group elements (Pt, Rh) and rare earth elements (La, Ce, etc.) has been conducted in a solid waste incinerator (SWI) with a state-of-the-art bottom ash treatment according to the Thermo-Re® concept. The SFA allowed the determination of the element partitioning in the SWI, as well as the elemental composition of the MSW by indirect analysis. The results show that the waste-input contains substantial quantities of precious metals, such as 0.4 ± 0.2mg/kg Au and 5.3 ± 0.7 mg/kg Ag. Many of the valuable substances, such as Au and Ag are enriched in specific outputs (e.g. non-ferrous metal fractions) and are therefore recoverable. As the precious metal content in MSW is expected to rise due to its increasing application in complex consumer products, the results of this study are essential for the improvement of resource recovery in the Thermo-Re® process.

Do We Have the Right Performance Indicators for the Circular Economy?: Insight into the Swiss Waste Management System

Summary A material flow analysis of the 2012 Swiss waste management system is presented, highlighting the material content available from waste. Half of municipal solid waste (MSW) is materially recycled and the other half thermally treated with energy recovery. A key component of an industrial ecosystem is increasing the resource efficiency through circulating materials. Recycling rates (RRs), an indicator for the circulating behavior of materials, are often used as measure for the degree of circularity of an economy. This study provides an in-depth analysis of the recycling of paper, cardboard, aluminum, tinplate, glass, and polyethylene terephthalate (PET) from MSW in Switzerland by splitting the RRs into closed- and open-loop collection rate (CR) and RRs. Whereas CR refers to collected material that enters the recycling process, RRs measure the available secondary resources produced from recycling processes. For PET, the closed-loop CR of 45% and the open-loop CR of 40% compare to an RR of 31% and 37%, respectively (including exports and recycling of polyethylene and metals from collection). Official collection rates for paper and cardboard are very high (97%), whereas CR of 74% and 89% and RR of 59% and 81% for paper and cardboard, respectively, were found in the present study (including export). For a majority of the separately collected materials investigated, the rates that are determined are substantially lower than those that are officially communicated. Furthermore, given that official rates often do not provide information on the availability of secondary materials, the improvement potential for increased resource recovery is hidden.

Influence of Input-Scrap Quality on the Environmental Impact of Secondary Steel Production

Summary In electric arc furnaces (EAFs), different grades of steel scrap are combined to produce the targeted carbon steel quality. The goal of this study is to assess the influence of scrap quality on the recycling process and on the final product by investigating the effect of the scrap mix composition, and other inputs, for example, preheating energy, on the electricity demand of the melting process. A large industrial data set (empirical data set of ∼20,000 individual heats recorded during 2.5 years at a Swiss EAF site) is analyzed using linear regression. The influence of scrap grades on electricity demand are found to correlate strongly with their respective quality; specific electricity demand is up to 45% higher for low-quality scrap than for high-quality scrap. Given that chemical compositions of scrap grades are highly variable and often unknown, average concentrations are determined using linear regression with scrap input as the predictors and the amounts of the investigated elements in liquid steel as the dependent variable. The lowest quality (highest copper and tin concentrations) and the highest electricity demand in the EAF are found for scrap recovered from bottom ashes of municipal solid waste incineration. Although even with low-quality scrap input steel recycling is environmentally superior to primary steel production, the optimization potential in terms of energy efficiency and resource recovery, for example, through pretreatment, seems to be substantial.

Abiotic resources: new impact assessment approaches in view of resource efficiency and resource criticality—55th Discussion Forum on Life Cycle Assessment, Zurich, Switzerland, April 11, 2014

Natural abiotic resources (here referring primarily to metals, minerals and fossil resources) have become a growing political concern with increased focus on resource scarcity, natural availability and dependency on foreign supply. For a nearterm time horizon, both the USA and the EU have identified so-called critical raw materials including platinum group metals, rare earth elements, etc. (EC 2010; NRC 2008), and resource efficiency has become one key element of the sustainability policy of the EU and Switzerland (EC 2011a; Bundesrat 2012). Within the context of life cycle assessment (LCA), the development of life cycle impact assessment (LCIA) methods has been very diverse without a unifying practice for how to assess the depletion of abiotic resources from the natural environment (Carvalho et al. 2014; EC 2011b; Klinglmair et al. 2013; Mancini et al. 2013). The overarching goal of the 55th Discussion Forum on LCA (DF-55) was to present and discuss recent developments of novel and updated LCIA approaches with respect to the relevance of resources as a separate safeguard subject (or area of protection, AoP) in environmental assessment, the rationale and interpretations of their respective environmental mechanisms related to abiotic resource depletion and the relation to other resource-related concerns such as scarcity and criticality. Setting the stage for the discussion forum, the first presentation of the day was given by Stefanie Hellweg (ETH Zurich, Switzerland) who gave an overview of the various issues related to the assessment of abiotic resource depletion. The extraction rates and the number of resources put into use are increasing and products are becoming more complex. The resulting heterogeneity of materials and products poses great challenges for recycling and recovery of the resources. In this context, three different methodologies for addressing different issues or questions related to the management of resources were outlined:

How can LCA support the circular economy?—63rd discussion forum on life cycle assessment, Zurich, Switzerland, November 30, 2016

The concept of circular economy (CE) conceives of a production and consumption systemwith minimal losses of materials and energy through extensive reuse, recycling and recovery (Ellen MacArthur Foundation 2013; European Environment Agency 2014) and is gaining popularity in Europe and elsewhere. Both the recycling of waste and a recycling friendly eco-design are components of CE. In previous studies, however, life cycle assessment has shown that closed loops are not always favourable from an environmental point of view (Laner and Rechberger 2007; Humbert et al. 2009; Geyer et al. 2015). Nevertheless, political initiatives focus on the path towards CE without the use of life cycle assessment (LCA) to evaluate actions and targets. The Swiss LCA Discussion Forum is a platform for the exchange between industry, consulting companies and LCA scientists. The 63rd Swiss LCADiscussion Forum aimed at discussing the following leading questions with representatives from academia, institutional representatives and visionaries: (i) How can LCA support the creation of a circular economy? (ii) How shall substituted materials and products be accounted for, who can claim the benefit, and how is resource quality taken into consideration? (iii) How can wastes and resources be managed to minimise their environmental impacts? To set the stage at the discussion forum, the CE concepts and the political aspects were presented. The following presentations focused on factors relevant for consideration when evaluating the benefits of a CE, such as waste and resource quality aspects and their influence on the recycling system, as well as product quality. Based on these presentations, a panel discussion tackled the leading questions above. Finally, six case studies on CE were shown, highlighting key findings and methodological issues when LCA is used as a tool to assess CE.

Linking energy scenarios and waste storylines for prospective environmental assessment of waste management systems

Multiple international and supranational organizations call upon changes in current waste management practices to play a key role in developing more sustainable economies. Life cycle assessment (LCA) is a popular method used to assess the sustainability of future waste management options. The uncertainties about future energy systems and waste compositions, however, may lead to ambiguous LCA results. One way to deal with this challenge is the development of joint energy and waste scenarios to investigate the robustness of waste management options. To date, joint energy and waste scenarios rely on the integration of large economic and engineering models. Complex models can hamper the transparency required for decision-makers to understand and implement LCA recommendations. Here we present the alternative of combining diverse energy scenarios and stakeholder-based waste storylines. This is a more qualitative approach than previous sustainable energy/waste evaluations and has a double aim: to address upfront the energy and waste composition sensitivity and enhance transparency by both relying on well-documented energy scenarios and involving stakeholders in the waste storyline formulation. We apply the approach to the Swiss municipal solid waste (MSW) management system in the context of the energy transition away from nuclear power. Three energy scenarios capture how radical the transition might be, while the storylines reflect societal developments and waste policies leading to low, high, and average MSW amounts. The approach delivers feasibility spaces of energy systems and waste compositions as input to the LCAs. It ensures a high level of transparency, which, in conjunction with the participation of decision-makers, has the potential to increase the chances of implementation of the recommendations based on LCA results.

Is there an environmentally optimal separate collection rate

Material recycling often leads to environmental benefits when compared to thermal treatments or landfilling and is therefore positioned in the waste hierarchy as the third priority after waste prevention and reuse. To assess the environmental impacts of recycling and the related substitution of primary material, linear steady-state models of physical flows are typically used. In reality, the environmental burdens of collection and recycling are likely to be a non-linear function of the collection rate. This short communication aims at raising awareness of the non-linear effects in separate collection systems and presents the first non-linear quantitative model for PET bottle recycling. The influence of collection rates on the material quality and the transport network is analyzed based on the data collected from industrial partners. The results highlight that in the present Swiss recycling system a very high collection rate close to 100% yields optimum environmental benefits with respect to global warming. The empirical data, however, provided indications for a decrease in the marginal environmental benefit of recycling. This can be seen as an indication that tipping points may exist for other recycling systems, in which the environmental benefits from substituting primary materials are less pronounced than they are for PET.

Modular life cycle assessment of municipal solid waste management

Life cycle assessment (LCA) is commonly applied to examine the environmental performance of waste management systems. The system boundaries are, however, often limited to either one tonne of material or to specific waste treatments and are, therefore, lacking a systems perspective. Here, a framework is proposed to assess complete waste management systems based on actual waste flows, assessed with a detailed material flow analysis (MFA) in a modular MFA/LCA approach. The transformation of the MFA into a product-process-matrix facilitates a direct link between MFA and LCA, therefore allowing for the assessment of variations in flows. To allow for an up-to-date and geographically specific assessment, 190 LCA modules were set up based on primary industrial data and the ecoinvent database. The LCA modules show where there have been improvements in different recycling processes over the past years (e.g. for paper recycling) and highlight that, from an environmental perspective, closed-loop recycling is not always preferable to open-loop recycling. In a case study, the Swiss municipal solid waste management system, of which there is already a detailed MFA, was modeled using the new LCA modules and applying the modular MFA/LCA approach. Five different mass flow distribution scenarios for the Swiss municipal solid waste management system were assessed to show the environmental impact of political measures and to test the sensitivity of the results to key parameters. The results of the case study highlight the importance of the dominant fractions in the overall environmental impacts assessment; while the metal fraction has the highest impact on a per kilogram basis, paper, cardboard, glass and mixed municipal solid waste were found to dominate the environmental impacts of the Swiss waste management system due to their mass. The scenarios also highlight the importance of the energy efficiency of municipal solid waste incineration plants and the credits from material substitution as key variables. In countries with advanced waste management systems such as Switzerland, there is limited improvement potential with further increases in recycling rates. In these cases, the focus of political measures should be laid on (i) the utilization of secondary materials in applications where they replace high-impact primary production, and (ii) an increased recovery of energy in waste-to-energy plants.