Integrating High-Resolution Material Flow Data into the Environmental Assessment of Waste Management System Scenarios: The Case of Plastic Packaging in Austria.

The environmental performance of the waste management system of plastic packaging in Austria was assessed using a combination of high-resolution material flows and input-dependent life cycle inventory data. These data were used to evaluate different configurations of the waste management system, reflecting the system structure as it was in 1994 in Austria and still is in some of the new EU member states, as well as a situation achieving the increased circular economy targets to be met by 2030. For the latter, two options, namely single-polymer recycling and mixed-polymer recycling, were investigated. The results showed that the status quo achieves net benefits for 15 out of 16 impact categories evaluated. Regarding the alternative scenarios, for most impact categories these benefits increased with increasing recycling rates, although for four impact categories the highest net benefit was achieved by the status quo. For many impact categories the marginal environmental benefit decreased at higher recycling rates, indicating that there is an environmentally optimal recycling rate below 100%. The results also highlight the importance of high-quality single-polymer plastics recycling from an environmental perspective because utilizing mixed polymer recycling to achieve circular economy targets would result in lower environmental benefits than the status quo.

Quantitative Analysis of Critical Factors for the Climate Impact of Landfill Mining.

Landfill mining has been proposed as an innovative strategy to mitigate environmental risks associated with landfills, to recover secondary raw materials and energy from the deposited waste, and to enable high-valued land uses at the site. The present study quantitatively assesses the importance of specific factors and conditions for the net contribution of landfill mining to global warming using a novel, set-based modeling approach and provides policy recommendations for facilitating the development of projects contributing to global warming mitigation. Building on life-cycle assessment, scenario modeling and sensitivity analysis methods are used to identify critical factors for the climate impact of landfill mining. The net contributions to global warming of the scenarios range from -1550 (saving) to 640 (burden) kg CO2e per Mg of excavated waste. Nearly 90% of the results' total variation can be explained by changes in four factors, namely the landfill gas management in the reference case (i.e., alternative to mining the landfill), the background energy system, the composition of the excavated waste, and the applied waste-to-energy technology. Based on the analyses, circumstances under which landfill mining should be prioritized or not are identified and sensitive parameters for the climate impact assessment of landfill mining are highlighted.

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.

Dynamic material flow modeling: an effort to calibrate and validate aluminum stocks and flows in Austria.

A calibrated and validated dynamic material flow model of Austrian aluminum (Al) stocks and flows between 1964 and 2012 was developed. Calibration and extensive plausibility testing was performed to illustrate how the quality of dynamic material flow analysis can be improved on the basis of the consideration of independent bottom-up estimates. According to the model, total Austrian in-use Al stocks reached a level of 360 kg/capita in 2012, with buildings (45%) and transport applications (32%) being the major in-use stocks. Old scrap generation (including export of end-of-life vehicles) amounted to 12.5 kg/capita in 2012, still being on the increase, while Al final demand has remained rather constant at around 25 kg/capita in the past few years. The application of global sensitivity analysis showed that only small parts of the total variance of old scrap generation could be explained by the variation of single parameters, emphasizing the need for comprehensive sensitivity analysis tools accounting for interaction between parameters and time-delay effects in dynamic material flow models. Overall, it was possible to generate a detailed understanding of the evolution of Al stocks and flows in Austria, including plausibility evaluations of the results. Such models constitute a reliable basis for evaluating future recycling potentials, in particular with respect to application-specific qualities of current and future national Al scrap generation and utilization.

Nitrogen pools and flows during lab-scale degradation of old landfilled waste under different oxygen and water regimes.

Nitrogen emissions from municipal solid waste (MSW) landfills occur primarily via leachate, where they pose a long-term pollution problem in the form of ammonium. In-situ aeration was proposed as a remediation measure to mitigate nitrogenous landfill emissions, turning the anaerobic environment to anoxic and subsequently aerobic. As in-depth studies of the nitrogen cycle during landfill aeration had been largely missing, it was the aim of this work to establish a detailed nitrogen balance for aerobic and anaerobic degradation of landfilled MSW based on lab-scale experiments, and also investigating the effect of different water regimes on nitrogen transformation during aeration. Six landfill simulation reactors were operated in duplicate under different conditions: aerated wet (with water addition and recirculation), aerated dry (without water addition) and anaerobic (wet). The results showed that more than 78 % of the initial total nitrogen (TNinit) remained in the solids in all set ups, with the highest nitrogen losses achieved with water addition during aeration. In this case, gaseous nitrogen losses (as N2 due to denitrification) amounted up to 16.6 % of TNinit and around 4 % of TNinit was discharged via leachate. The aerated dry set-up showed lower denitrification rates (2.6-8.8 % of TNinit was released as N2), but was associated with the highest N2O emissions (3.8-3.9 % of TNinit). For the anaerobic treatment the main pathway of nitrogen discharge was the leachate, where NH4 accounted for around 8 % of TNinit. These findings provide the basis for improved management strategies to enhance nitrogen removal during in-situ aeration of old landfills.

Site-specific criteria for the completion of landfill aftercare.

Municipal solid waste (MSW) landfills need to be managed after closure to assure long-term environmental compatibility. Aftercare can be completed when the authorities consider the landfill not likely to pose a threat to humans and the environment. In this work, a methodology for deriving site-specific aftercare completion criteria is presented and its application is illustrated via a case study. The evaluation method combines models addressing waste emission behavior, long-term barrier performance, and pollutant migration to assess the potential impact of landfill emissions on the environment. Based on the definition of acceptable impact levels at certain points of compliance, scenario- and pollutant-specific aftercare completion criteria are derived. The methodology was applied to a closed MSW landfill in Austria and potential aftercare durations were determined. While landfill gas emissions may become environmentally tolerable within decades at the site, leachate-related aftercare measures were expected to be necessary for centuries (primarily as a result of ammonium). Although the evaluation comes with large uncertainties, it allows for linking aftercare intensity and duration with respect to an environmentally compatible state of the landfill in the absence of aftercare. However, further case studies including regulatory review and acceptance are needed to use the methodology in a decision support tool on aftercare completion.

A systematic review of life cycle assessment of solid waste management: Methodological trends and prospects.

Solid waste disposal has led to increasing concerns over resource, health, and environmental problems. These issues have been investigated using the Life Cycle Assessment (LCA) technique which helps identify the roots of varying hazards and allows decision-makers to improve the environmental performance of waste management practices. However, there is a lack of review studies that conducted meta-analysis related to developments in critical methodological steps of LCA on solid waste management. To fill this gap, this review paper examines 15 elements comprising the preference of journals, 13 LCA method-related characteristics, and economic assessment. Insights on the limitations and current practices of LCA applications, along with trends for future research, are provided. 240 studies on the LCA of SWM from 2009 until 2020 were systematically reviewed and classified into two major year-groups (i.e., 2009-2014 and 2015-2020) to investigate the trend changes. Among the studied elements, it is found that energy-related applications are on the increase in LCA studies on solid waste management. Anaerobic digestion facilities nearly double in appearance in the second year-group (2015-2020). There is also a more frequent occurrence of certain characterization methods like ReCiPe and CML. Functional units become more diverse, but are overall mostly defined on a mass basis. A frequently identified issue of many LCAs on solid waste management is the ambiguity of data sources such as out-of-date literature or inconsistent geographical references. By addressing issues of methodological standardization, this review study provides a basis to further increase the reliability of results of future LCA studies on solid waste management.

Environmental compatibility of closed landfills - assessing future pollution hazards.

Municipal solid waste landfills need to be managed after closure. This so-called aftercare comprises the treatment and monitoring of residual emissions as well as the maintenance and control of landfill elements. The measures can be terminated when a landfill does not pose a threat to the environment any more. Consequently, the evaluation of landfill environmental compatibility includes an estimation of future pollution hazards as well as an assessment of the vulnerability of the affected environment. An approach to assess future emission rates is presented and discussed in view of long-term environmental compatibility. The suggested method consists (a) of a continuous model to predict emissions under the assumption of constant landfill conditions, and (b) different scenarios to evaluate the effects of changing conditions within and around the landfill. The model takes into account the actual status of the landfill, hence different methods to gain information about landfill characteristics have to be applied. Finally, assumptions, uncertainties, and limitations of the methodology are discussed, and the need for future research is outlined.

The multidimensional effects of single-use and packaging plastic strategies on German household waste management.

Single-use and packaging plastic (SUPP) strategies are intended to transform the linear make-use-dispose economy of SUPPs into a more circular, resource-efficient one. The aim of this study was to identify optimal SUPP management concepts from a circular-economy-perspective by assessing the effects of different SUPP strategies on household waste management. Data on the generation and management of SUPP-containing household waste in Germany in 2017 were compiled and a material flow model was established. Regulatory SUPP strategies were translated into scenarios (with effects on waste generation and waste composition) and implemented in the material flow model. The effects on material efficiency, waste generation and lower heating values were evaluated and trade-offs between these target dimensions were identified. In Germany in 2017, 32 kg per person and year of SUPP household waste were generated, of which 28 kg per person and year was packaging waste. From a material efficiency perspective, the combination of banning specific non-packaging SUPPs and optimizing source-separation leads to the maximum increase in final recycling rates of SUPPs in household waste, from 38% to 50%. However, in this scenario the amount of SUPP-containing household waste is hardly reduced as compared to the status quo. The trade-offs observed in different waste management target dimensions highlight the importance of understanding the systemic effects of SUPP strategies on waste management in order to identify optimal solutions from a circular-economy-perspective.

Landfill mining in Europe: Assessing the economic potential of value creation from generated combustibles and fines residue.

Previous studies showed that resources recovery through landfill mining (LFM) is generally challenging from an economic perspective and that a large share of project costs is related to the external treatment and disposal of bulk process wastes such as combustibles and fines residue. Building on these analyses, this study aims to explore the potential for improving the economy of LFM in Europe by creating value from these bulk process wastes. Specifically, the combustibles are treated through internal incineration with subsequent energy recovery, while fines residue is utilized as construction aggregates. These explored possibilities are investigated considering other varying factors at the site, project, and system levels that cover possible LFM project settings in Europe. A set-based modelling approach is adapted to generate multiple LFM scenarios (531,441) and investigate the underlying critical factors that drive the economy of LFM through global sensitivity analysis. Results show that an additional 16% of LFM scenarios become net profitable, mainly driven by fines residue utilization. Avoided costs for re-landfilling are higher than the revenues from construction aggregates. By contrast, internal incineration is driven by the revenues from recovered energy rather than the avoided gate fee, which is substituted by the costs for building and operating own plants. Overall, the policy conditions remain critical to further improve the economy of LFM in Europe. Recommendations include an inclusive quality standard that relies on pollutant leachability rather than total concentration for higher-value application of fines residue and incentive rather than taxation for producing renewable energy from the combustibles.

Material efficiency to measure the environmental performance of waste management systems: A case study on PET bottle recycling in Austria, Germany and Serbia.

Material efficiency measures, such as recycling rates, are often used to set circular economy targets to achieve higher resource efficiency and lower environmental impact. The aim of this study was to identify material efficiency indicators suitable to reflect the environmental performance of waste and recycling systems using PET bottle waste management in three European countries with diverse waste management structures and recycling performance levels. Material flow analysis and life cycle assessment were performed to assess the material efficiency and environmental impacts of each system as a basis to analyze the relation between these two dimensions. PET bottle waste generation was 5.4 kg/person and year (pa) in Austria in 2013, 6.0 kg/pa in Germany in 2017 and 6.9 kg/pa in Serbia in 2015. Out of this waste flow 41%, 91%, and 11% were directed into PET recyclate in Austria, Germany and Serbia, respectively. For all systems, higher material efficiency translated into lower environmental impact and vice versa. However, linear regression analysis between different material efficiency indicators and environmental impacts showed that indicators targeted at actual recycling, specifically at closed loop, were better suited to reflect environmental performance than input-based indicators. Therefore, whenever data are available, output-based quality-related indicators should be used to measure the material efficiency of waste and resource systems because they correlate best with the goals of increasing resource efficiency and decreasing environmental impacts.

Flooding of municipal solid waste landfills--an environmental hazard?

Municipal solid waste (MSW) landfills pose a long-lasting risk for humans and the environment. While landfill emissions under regular operating conditions are well investigated, landfill behaviour and associated emissions in case of flooding are widely unknown, although damages have been documented. This paper aims at developing a methodology for determining the proportion of MSW landfills endangered by flooding, and at evaluating the impact flooded landfills might have on the environment during a flood event. The risk of flooding of MSW landfills is assessed by using information about flood risk zones. Out of 1064 landfills investigated in Austria, 312 sites or about 30% are located in or next to areas flooded on average once in 200 years. Around 5% of these landfills are equipped with flood protection facilities. Material inventories of 147 landfill sites endangered by flooding are established, and potential emissions during a flood event are estimated by assuming the worst case of complete landfill leaching and erosion. The environmental relevance of emissions during flooding is discussed on the basis of a case study in the western part of Austria. Although environmental hazards need to be assessed on a site- and event-specific basis, the results indicate that flooded MSW landfills represent in general small environmental risks for the period of flooding. The longer term consequences of flooding are discussed in a next paper.

Quantitative evaluation of waste prevention on the level of small and medium sized enterprises (SMEs).

Waste prevention is a principle means of achieving the goals of waste management and a key element for developing sustainable economies. Small and medium sized enterprises (SMEs) contribute substantially to environmental degradation, often not even being aware of their environmental effects. Therefore, several initiatives have been launched in Austria aimed at supporting waste prevention measures on the level of SMEs. To promote the most efficient projects, they have to be evaluated with respect to their contribution to the goals of waste management. It is the aim of this paper to develop a methodology for evaluating waste prevention measures in SMEs based on their goal orientation. At first, conceptual problems of defining and delineating waste prevention activities are briefly discussed. Then an approach to evaluate waste prevention activities with respect to their environmental performance is presented and benchmarks which allow for an efficient use of the available funds are developed. Finally the evaluation method is applied to a number of former projects and the calculated results are analysed with respect to shortcomings and limitations of the model. It is found that the developed methodology can provide a tool for a more objective and comprehensible evaluation of waste prevention measures.

Systematic assessment of critical factors for the economic performance of landfill mining in Europe: What drives the economy of landfill mining?

Landfill mining (LFM) is a strategy to mitigate environmental impacts associated with landfills, while simultaneously recovering dormant materials, energy carriers, and land resources. Although several case study assessments on the economy of LFM exist, a broader understanding of the driving factors is still lacking. This study aims at identifying generically important factors for the economy of LFM in Europe and understanding their role in developing economically feasible projects in view of different site, project and system-level conditions. Therefore, a set-based modeling approach is used to establish a large number (531,441) of LFM scenarios, evaluate their economic performance in terms of net present value (NPV), and analyze the relationships between input factors and economic outcome via global sensitivity analysis. The scenario results range from -139 Euro to +127 Euro/Mg of excavated waste, with 80% of the scenarios having negative NPVs. Variations in the costs for waste treatment and disposal and the avoided cost of alternative landfill management (i.e. if the landfill was not mined) have the strongest effect on the scenario NPVs, which illustrates the critical role of system level factors for LFM economy and the potential of policy intervention to incentivize LFM. Consequently, system conditions should guide site selection and project development, which is exemplified in the study for two extreme regional archetypes in terms of income and waste management standard. Future work should further explore the developed model to provide decision support on LFM strategies in consideration of alternative purposes, stakeholders, and objectives.

Circular economy of plastic packaging: Current practice and perspectives in Austria.

Plastics, especially from packaging, have gained increasing attention in waste management, driving many policy initiatives to improve the circularity of these materials in the economy to increase resource efficiency. In this context, the EU has proposed increasing targets to encourage the recycling of (plastic) packaging. To accurately calculate the recycling rates, detailed information on the flows of plastic packaging is needed. Therefore, the aim of this paper is to quantitatively and qualitatively investigate the waste management system for plastic packaging in Austria in 2013 using material flow analysis, taking into account the used product types and the polymer composition. The results show that 300,000 ±â€¯3% t/a (35 kg/cap·a) of waste plastic packaging were produced, mainly composed of large and small films and small hollow bodies, including PET bottles. Correspondingly, the polymer composition of the waste stream was dominated by LDPE (46% ±â€¯6%), PET (19% ±â€¯4%) and PP (14% ±â€¯6%). 58% ±â€¯3% was collected separately, and regarding the final treatment, 26% ±â€¯7% of the total waste stream was recovered as re-granulates, whereas the rest was thermally recovered in waste-to-energy plants (40% ±â€¯3%) and the cement industry (33% ±â€¯6%). The targets set by the EU and Austria were reached comfortably, although to reach the proposed future target major technological steps regarding collection and sorting will be needed. However, the current calculation point of the targets, i.e. on the input side of the recycling plant, is not deemed to be fully in line with the overall objective of the circular economy, namely to keep materials in the economy and prevent losses. It is therefore recommended that the targets be calculated with respect to the actual output of the recycling process, provided that the quality of the output products is maintained, to accurately assess the performance of the waste management system.

Comparative life cycle assessment of MSWI fly ash treatment and disposal.

Municipal solid waste incineration (MSWI) fly ash constitutes a hazardous waste. The possibilities for managing this waste comprise disposal at underground deposits or at above-ground landfills after cement stabilisation, application of the FLUREC process, thermal treatment in a dedicated furnace or thermal co-treatment together with combustible hazardous waste. A comparative life cycle assessment (LCA) study was conducted in order to assess the environmental impact of these five MSWI fly ash disposal options with regard to two different time horizons (100years, indefinite). The uncertainties of the input parameters were propagated by Monte Carlo simulations (MCS). As could be shown by the discernibility analysis, the FLUREC process has the lowest impact in more than 90% of the MCS results. In case long-term emissions (beyond 100years) are neglected, the second lowest impact is caused by thermal co-treatment in more than 90% of the MCS results. Consideration of long-term emissions indicates the disposal at underground deposits as second best option. Furthermore, it is shown that stabilisation with cement has the second highest and thermal treatment in a dedicated furnace has the highest environmental impact, mostly due to high CO2 emissions. Therefore these two treatment options should be avoided in the future. Besides the comparative evaluation of the different options, it could be shown that uncertainty analysis is useful to determine the relevance of long-term emissions for the ranking of different systems.

Added Values of Time Series in Material Flow Analysis: The Austrian Phosphorus Budget from 1990 to 2011.

Material flow analysis is a tool that is increasingly used as a foundation for resource management and environmental protection. This tool is primarily applied in a static manner to individual years, ignoring the impact of time on the material budgets. In this study, a detailed multiyear model of the Austrian phosphorus budget covering the period 1990-2011 was built to investigate its behavior over time and test the hypothesis that a multiyear approach can also contribute to the improvement of static budgets. Further, a novel method was applied to investigate the quality and characteristics of the data and quantify the uncertainty. The degree of change between the budgets was assessed and showed that approximately half of the flows have changed significantly and, at times, abruptly since 1990, but it is not possible to distinguish unequivocally between constant and moderately changing flows given their uncertainty. The study reveals that the phosphorus transported in waste flows has increased more rapidly than its recovery, which accounted for 55% to 60% of the total waste phosphorus in 1990 and only 40% in 2011. The loss ratio in landfills and cement kilns has oscillated in the range of 40% to 50%. From a methodological point of view, the multiyear approach has broadened the conceptual model of the budget, making it more suitable as a basis for material accounting and monitoring. Moreover, the analysis of the data reconciliation process over a long period of time proved to be a useful tool for identifying systematic errors in the model.

Carbon pools and flows during lab-scale degradation of old landfilled waste under different oxygen and water regimes.

Landfill aeration has been proven to accelerate the degradation of organic matter in landfills in comparison to anaerobic decomposition. The present study aims to evaluate pools of organic matter decomposing under aerobic and anaerobic conditions using landfill simulation reactors (LSR) filled with 40 year old waste from a former MSW landfill. The LSR were operated for 27 months, whereby the waste in one pair was kept under anaerobic conditions and the four other LSRs were aerated. Two of the aerated LSR were run with leachate recirculation and water addition and two without. The organic carbon in the solid waste was characterized at the beginning and at the end of the experiments and major carbon flows (e.g. TOC in leachate, gaseous CO2 and CH4) were monitored during operation. After the termination of the experiments, the waste from the anaerobic LSRs exhibited a long-term gas production potential of more than 20 NL kg(-1) dry waste, which corresponded to the mineralization of around 12% of the initial TOC (67 g kg(-1) dry waste). Compared to that, aeration led to threefold decrease in TOC (32-36% of the initial TOC were mineralized), without apparent differences in carbon discharge between the aerobic set ups with and without water addition. Based on the investigation of the carbon pools it could be demonstrated that a bit more than 10% of the initially present organic carbon was transformed into more recalcitrant forms, presumably due to the formation of humic substances. The source of anaerobic degradation could be identified mainly as cellulose which played a minor role during aerobic degradation in the experiment.

Resource recovery from residual household waste: An application of exergy flow analysis and exergetic life cycle assessment.

Exergy is based on the Second Law of thermodynamics and can be used to express physical and chemical potential and provides a unified measure for resource accounting. In this study, exergy analysis was applied to four residual household waste management scenarios with focus on the achieved resource recovery efficiencies. The calculated exergy efficiencies were used to compare the scenarios and to evaluate the applicability of exergy-based measures for expressing resource quality and for optimizing resource recovery. Exergy efficiencies were determined based on two approaches: (i) exergy flow analysis of the waste treatment system under investigation and (ii) exergetic life cycle assessment (LCA) using the Cumulative Exergy Extraction from the Natural Environment (CEENE) as a method for resource accounting. Scenario efficiencies of around 17-27% were found based on the exergy flow analysis (higher efficiencies were associated with high levels of material recycling), while the scenario efficiencies based on the exergetic LCA lay in a narrow range around 14%. Metal recovery was beneficial in both types of analyses, but had more influence on the overall efficiency in the exergetic LCA approach, as avoided burdens associated with primary metal production were much more important than the exergy content of the recovered metals. On the other hand, plastic recovery was highly beneficial in the exergy flow analysis, but rather insignificant in exergetic LCA. The two approaches thereby offered different quantitative results as well as conclusions regarding material recovery. With respect to resource quality, the main challenge for the exergy flow analysis is the use of exergy content and exergy losses as a proxy for resource quality and resource losses, as exergy content is not per se correlated with the functionality of a material. In addition, the definition of appropriate waste system boundaries is critical for the exergy efficiencies derived from the flow analysis, as it is constrained by limited information available about the composition of flows in the system as well as about secondary production processes and their interaction with primary or traditional production chains. In the exergetic LCA, resource quality could be reflected by the savings achieved by product substitution and the consideration of the waste's upstream burden allowed for an evaluation of the waste's resource potential. For a comprehensive assessment of resource efficiency in waste LCA, the sensitivity of accounting for product substitution should be carefully analyzed and cumulative exergy consumption measures should be complimented by other impact categories.