Critical choices in Waste LCA – A case study on the treatment of PAH‐ rich road debris

Life cycle assessment (LCA) is well established to provide decision support on the design of waste management systems. It offers a holistic perspective on waste flows, treatment options and environmental impacts. Despite the holistic approach and the general relevance of LCA, it needs to be emphasized that results are contextspecific and depend on the goal and scope of the LCA model as well as on the local conditions of the waste management system (Laurent et al. 2014a). Apart from the LCA setting, methodological choices and data availability play a crucial role for the validity and reliability of waste LCA results (Laurent et al. 2014b). Therefore, the effect of specific choices and assumptions on the results needs to be reflected by appropriate analyses, such as scenario, sensitivity and uncertainty analysis. This study uses the case of treating German road debris rich in polycyclic aromatic hydrocarbons (PAH) to illustrate the effect of different LCA model choices on the environmental impacts associated with different treatment routes. Because PAH-rich road debris is designated as hazardous waste it cannot be directly utilized, but needs to be thermally treated before mineral aggregates can be recycled. Alternatively, it can be landfilled/used as a landfill construction material (after mechanical treatment). In this study, different thermal treatment options (all based on rotary kiln technology) for PAH-rich road debris generated in Kassel were compared among each other and with the two landfilling options. Material and energy balances as well as transport scenarios were established for each treatment path. Data for the foreground system was available from plant operators or collected from existing LCA studies. Background data was retrieved from ecoinvent Version 3.7. LCA modelling was performed using the open source LCA framework Brightway2 (https://brightway.dev/) and environmental impacts were expressed via 14 mid-point impact categories. In order to understand the effect of different choices, scenario and sensitivity analyses were performed. The variation of factors comprised transport distances and transport datasets, energy efficiencies of thermal treatment, and choices regarding the substitution related to produced heat and power as well as related to mineral aggregates and primary mineral raw materials. Furthermore, aspects of data quality associated with the assessment of existing (full-scale operation) vs. prospective (lab-scale experiments) technology were discussed. Major findings of the LCA were that energy-efficient thermal treatment of PAH-rich road debris is preferable to landfilling in 13 out of 14 impact categories. The exception was climate change, where the deposition at the landfill resulted in 3- times lower greenhouse gas emissions (around 20 kg CO2-equ. per Mg of waste) than thermal treatment. For all the other impact categories thermal treatment with effective energy recovery performed better than landfilling, with particularly large advantages regarding human toxicity, ecotoxicity, and fossil resource depletion. With respect to thermal treatment, it was found that for the prospective technology options the uncertainty associated with the results outweighed the differences between the individual results for these prospective options. Critical factors in this context were energy efficiencies of the plants and substitution choices regarding electricity mix as well as primary materials. Also transport modes and distances turned out to have a relevant effect on the results. The effect of these choices highlighted that LCA results need to be interpreted in the context of the goal and scope as well the methodological framework of the study and that the general validity should not be overstated. Literature: Laurent et al. (2014a): Review of LCA studies of solid waste management systems – Part I: Lessons learned and perspectives, Waste Management 34. https://doi.org/10.1016/j.wasman.2013.10.045. Laurent et al. (2014b): Review of LCA studies of solid waste management systems – Part II: Methodological guidance for a better practice Waste Management 34. https://doi.org/10.1016/j.wasman.2013.12.004

An LCA-based performance indicator for plastic packaging waste management systems

Material flow-based indicators are a common tool to measure the performance of waste management systems. For example, in the EU recycling rates are used to set targets for circular economy and environmental policies (cf. 94/62/EC, 2008/98/EC). However, the suitability of recycling rates to measure the progress regarding the transformation of a rather linear economy into a more sustainable circular one is limited. Several previous studies showed that recycling rates and other material flow-based indicators do not necessarily correlate with the environmental performance of waste management systems (cf. Haupt et al., 2018; Van Eygen et al., 2018; Schmidt et al., 2020; Rigamonti and Mancini 2021). For example, in the case of plastic packaging waste, recycling rates do not correlate with toxicity related environmental impacts (Schmidt et al., 2020). Another known limitation of recycling rates is that they cannot appropriately reflect waste prevention and reuse activities. Furthermore, recycling rates do typically not account for the fluctuating quality of recycling outputs and the associated functionality of recycled materials. Nevertheless, a major advantage of recycling rates is that they are straightforward to measure and easy to communicate. The aim of this study was to overcome the shortcomings of recycling rates while maintaining the comprehensibility of material flow-based indicators by developing a new LCA-based performance indicator for the plastic packaging waste management system in Germany. The proposed indicator is a further development of the waste hierarchy index by Pires and Martinho (2019). Following the waste hierarchy index, the proposed indicator is calculated as the weighted sum of waste flows to different treatment paths divided by the total amount of waste generated. The special characteristic of the new indicator is that its weighting factors are derived from LCA results of available waste treatment options depending on the type of waste assessed. For example, in the case of plastic packaging waste, relevant waste treatment paths are the separate collection and processing of reusable PET bottles, the separate collection of single-use PET bottles (part of the German deposit-refund system), the separate collection of plastic packaging waste as part of the mixed light weight packaging waste as well as the treatment of miss-sorted plastic packaging waste items. Besides to well-established treatment paths, prospective treatment paths, as the chemical recycling of separately collected plastic packaging waste are provided. Next to the total indicator score (based on 16 impact categories) information on best and worst scoring impact categories are provided to communicate possible trade-offs. The proposed indicator is suited to assess the environmental performance of a product in a specific waste management system or the waste management system itself in its current and possible future states. The indicator will be introduced, and its use will be illustrated using a case study on plastic packaging waste management in Germany. References Haupt, M., Waser, E., Würmli, J.C., Hellweg, S., (2018): Is there an environmentally optimal separate collection rate? Waste Management 77, 220–224. https://doi.org/ 10.1016/j.wasman.2018.03.050. Pires, Ana; Martinho, Graça (2019): Waste hierarchy index for circular economy in waste management. In: Waste management (New York, N.Y.) 95, S. 298–305. DOI: 10.1016/j.wasman.2019.06.014. Rigamonti, L.; Mancini, E. (2021): Life cycle assessment and circularity indicators. In: Int J Life Cycle Assess 26 (10), S. 1937–1942. DOI: 10.1007/s11367-021-01966-2. Schmidt, S., Laner, D., Van Eygen, E., Stanisavljevic, N., (2020): Material efficiency to measure the environmental performance of waste management systems: A case study on PET bottle recycling in Austria, Germany and Serbia. Waste Management 110, 74–86. tps://doi.org/10.1016/j.wasman.2020.05.011. Van Eygen, E., Laner, D., Fellner, J., 2018. Integrating high-resolution material flow data into the environmental assessment of waste management system scenarios: the case of plastic packaging in Austria. Environ. Sci. Technol. 52 (19), pp. 10934–10945. https://doi.org/10.1021/acs.est.8b04233

Systematic evaluation of critical factors for the climate impact of landfill minin

In Europe several hundreds of thousands of old landfills exist, which are associated with long-term environmental impacts, extensive aftercare periods, and land-use restrictions potentially interfering with regional development plans. The potential of landfill mining for mitigating environmental pollution and valorising deposited wastes via material and energy recovery was investigated in various studies addressing ecologic and/or economic implications of landfill mining. With respect to global warming, some studies identified landfill mining as a net contributor, while others indicated that landfill mining results in a lower climate impact compared to the do-nothing alternative. Although all of these studies state that the actual environmental performance of landfill mining depends on various case-specific factors, so far a systematic assessment of the importance of individual factors for the environmental impact of landfill mining is missing. This research gap is addressed by the present study, which aims to quantitatively assess the importance of specific factors and conditions for the contribution of landfill mining to global warming. Therefore, we identify site-specific factors, project settings and system conditions, which are potentially relevant for the climate impact of a landfill mining project (cf. Figure 1). Based on the investigation of the influence of these factors, settings, and conditions, respectively, on a landfill mining’s contribution to global warming, we discuss the practical implications of our findings in terms of strategies and measures for implementation of landfill mining. Please click Additional Files below to see the full abstract

Material Cycles and Chemicals: Dynamic Material Flow Analysis of Contaminants in Paper Recycling

This study provides a systematic approach for assessment of contaminants in materials for recycling. Paper recycling is used as an illustrative example. Three selected chemicals, bisphenol A (BPA), diethylhexyl phthalate (DEHP) and mineral oil hydrocarbons (MOHs), are evaluated within the paper cycle. The approach combines static material flow analysis (MFA) with dynamic material and substance flow modeling. The results indicate that phasing out of chemicals is the most effective measure for reducing chemical contamination. However, this scenario was also associated with a considerable lag phase (between approximately one and three decades) before the presence of chemicals in paper products could be considered insignificant. While improved decontamination may appear to be an effective way of minimizing chemicals in products, this may also result in lower production yields. Optimized waste material source-segregation and collection was the least effective strategy for reducing chemical contamination, if the overall recycling rates should be maintained at the current level (approximately 70% for Europe). The study provides a consistent approach for evaluating contaminant levels in material cycles. The results clearly indicate that mass-based recycling targets are not sufficient to ensure high quality material recycling