•PET is suitable for multiple times closed-loop recycling of mixed food packaging.•Recycled PE from Danish HHW shows high tensile strength.•Homogeneity regarding product types is key in preserving ...quality of PE & PP waste.•Many product types in PP waste hinder closed-loop recycling into new packaging.•Degradation of PP during recycling limits the applicability of recycled PP from HHW.
Recycling of plastic is an important step towards circular economy. However, plastic from household waste (HHW) is a heterogeneous and contaminated resource, leading to recycled plastic with reduced quality, limiting the potential for closed-loop recycling. In addition to regulatory requirements for the chemical composition of recycled plastic, reduced physical and mechanical properties may limit the potential for closed-loop recycling. Consequently, this study analyses the thermal degradation, processability and mechanical properties of a range of reprocessed PET, PE and PP samples from source-separated plastic in HHW. On this basis, the potential for closed-loop recycling is evaluated. The study demonstrated that PET, PE and PP recycling represent different challenges. Potential degradation of the PET polymer can be reversed in a decontamination process, making PET waste well-suited for closed-loop, multiple times recycling, even when the degree of heterogeneity in the waste is high. The processability of different kinds of PE and PP packaging types varied considerably, especially for PP. Consequently, current recycling of mixed PP waste and even separate recycling of individual PP waste packaging types, will not technically facilitate recycling into new packaging products. This highlights the importance of PE and PP waste homogeneity when sent to reprocessing. Such homogeneity may be achieved through additional plastic sorting and regulatory harmonisation of product design, accounting for polymer properties and recyclability. Degradation of PP during recycling was shown to be substantial, representing another important limitation for PP recycling, necessary to address in the future.
•More than 90% of the source-separated rigid plastic waste was PET, PE or PP.•Food- and non-food packaging existed in all three polymers.•High occurrence of products made of multiple polymers in the ...waste.•Products designed for recycling can increase quantities of recycled plastic.•Separate management of food packaging can lead to closed-loop recycling.
Recycling of plastic from household waste (HHW) is crucial in the transition towards a circular plastic economy. Plastic from HHW consists of numerous immiscible polymers, product types and product designs (e.g. colour, polymer separability), which often lead to considerable physical losses during sorting, and low-quality recycled plastic. Consequently, recycling initiatives have been proposed to enhance the quantity and quality of plastic recycling from HHW. To quantify the potential effects of such initiatives, a detailed composition of plastic waste is necessary. The aim was to provide such detailed composition of Danish source-separated rigid plastic waste, including information regarding the polymer of the main product component, product type, polymer design and separability as well as colour. The potential effects on recycled quantity and quality from implementing selected recycling initiatives were quantified and recommendations provided. PET, PE and PP made up >90% of the source-separated plastic and both food- and non-food packaging existed in all three polymers. In total, 10–11% of the plastic was black, and around 44% consisted of multiple polymers, of which one-third was non-separable. Initiatives improving product design for recycling will likely result in increased quantity of recycled plastic. By effectively separating food from non-food packaging, e.g. by introducing two bins in the households or politically aligning polymers and product types (all food packaging in PET and PP, all non-food packaging in PE), 39–63% of the waste could potentially be recycled in a closed loop into food-grade quality packaging. The overall highest benefits were reached by combining initiatives.
•High leaching of PO43−, Mg, Zn, Cu and Cd for pH conditions relevant to acidic soils.•Wood ash leaching was described adequately by a geochemical speciation model.•The source-term release of Cd was ...of potential concern compared with SQC.•Similar soil application dosages may result in different liming effects.
In Denmark, increasing amounts of wood ashes are generated from biomass combustion for energy production. The utilisation of ashes on top of forest soil for liming purposes has been proposed asan alternative to landfilling. Danish wood ash samples were collected and characterised with respect to chemical composition, mineralogy and leaching properties (batch leaching at L/S 2 and 10L/kg, and pH-dependent leaching at 10L/kg). Large variations in the ash liming properties were observed (ANC7.5: 1.8–6.4meqH+/g), indicating that similar soil application dosages may result in different liming effects. High contents of Ca, Si, P, K and Mg were observed in all samples, while the highest contents of S and N were found in fly ashes and mixed ashes (combination of fly and bottom ashes). Similarly, the highest contents of some trace metals, e.g. Cd, Mo and Se, were observed for fly ash. Releases of major, minor and trace elements were affected significantly by pH: high releases of PO43−, Mg, Zn, Cu and Cd were found for acidic conditions relevant to forest soils, while the highest releases of Mo and Cr were observed in alkaline conditions. Mineral phases were selected based on XRD analyses and the existing literature, and they were applied as inputs for the geochemical modelling of pH-dependent leaching. Mineral dissolution was found adequate for a wide range of major elements and nutrients, while the description of trace elements could be done only for parts of the pH-range. Content and leaching of PAHs were observed below detection limits. The source-term release of Ca, K, Mg, Mn, and P in acidic conditions relevant to forest soils was higher than ten years of atmospheric deposition, in contrast to the relatively low release of Al, Fe and Na. The potential release of Cd was found to be the most critical element compared with soil quality criteria, whereas the maximum theoretical loads of Ba, Cd, Cr, Sr, Mo, Ni, Pb, Sb, Se, Sn and V were relatively low.
•All waste paper samples contained BPA, while BPS was found in 73% of them.•Except for BPS, use of BPA phenol-based analogues appeared to be limited.•Major flux of BPA and BPS in household waste ...paper came from four fractions.•The majority of thermal paper receipts contained either BPA or BPS.•BPA and its analogues could potentially persist in paper recycling.
Bisphenol A (BPA) is an industrial chemical produced in large volumes. Its main use is associated with polycarbonate plastic, epoxy resins and thermal paper. In contrast to other applications, thermal paper contains BPA in its un-reacted form as an additive, which is subjected to migration. Receiving a significant amount of attention from the scientific community and beyond, due to its controversial endocrine-disrupting effects, the industry is attempting to substitute BPA in variety of applications. Alternative phenolic compounds have been proposed for use in thermal paper; however, information to what extent BPA alternatives have been used in paper is sparse. The aim of the present work was to quantify BPA and its alternatives (bisphenol S (BPS), bisphenol E (BPE), bisphenol B (BPB), 4-cumylphenol (HPP) and bisphenol F (BPF)) in waste paper and board from Danish households, thermal paper receipts, non-carbon copy paper and conventional printer paper. BPA was found in all waste paper samples analysed, while BPS was identified in 73% of them. Only BPB was not identified in any of the samples. BPA and BPS were found in the majority of the receipts, which contained no measurable concentrations of the remaining alternatives. Although receipts showed the highest concentrations of BPA and BPS, office paper, flyers and corrugated boxes, together with receipts, represented the major flux of the two compounds in waste paper streams.
•BFRs were analysed in plastics from household waste, virgin and recycled plastics.•Half (50%) of household waste plastics contained BFRs.•Concentrations up to 26,000,000ngTBBPA/g were measured in ...some recycled plastics.•Widespread presence of BFRs indicated unintended addition or chemical degradation.
Flame retardants are chemicals vital for reducing risks of fire and preventing human casualties and property losses. Due to the abundance, low cost and high performance of bromine, brominated flame retardants (BFRs) have had a significant share of the market for years. Physical stability on the other hand, has resulted in dispersion and accumulation of selected BFRs in the environment and receiving biota. A wide range of plastic products may contain BFRs. This affects the quality of waste plastics as secondary resource: material recycling may potentially reintroduce the BFRs into new plastic product cycles and lead to increased exposure levels, e.g. through use of plastic packaging materials. To provide quantitative and qualitative data on presence of BFRs in plastics, we analysed bromophenols (tetrabromobisphenol A (TBBPA), dibromophenols (2,4- and 2,6-DBP) and 2,4,6-tribromophenol (2,4,6-TBP)), hexabromocyclododecane stereoisomers (α-, β-, and γ-HBCD), as well as selected polybrominated diphenyl ethers (PBDEs) in samples of household waste plastics, virgin and recycled plastics. A considerable number of samples contained BFRs, with highest concentrations associated with acrylonitrile butadiene styrene (ABS, up to 26,000,000ngTBBPA/g) and polystyrene (PS, up to 330,000ng∑HBCD/g). Abundancy in low concentrations of some BFRs in plastic samples suggested either unintended addition in plastic products or degradation of higher molecular weight BFRs. The presence of currently restricted flame retardants (PBDEs and HBCD) identified in the plastic samples illustrates that circular material flows may be contaminated for extended periods. The screening clearly showed a need for improved documentation and monitoring of the presence of BFRs in plastic waste routed to recycling.
•Plastic from households contained higher metal concentrations than virgin plastic.•Reprocessed plastic from household waste had the highest metal concentrations.•PET plastic contained significantly ...more Sb than PE, PP and PS plastics.•“Dirt” has limited contribution to the presence of metals in waste plastics.•Higher recycling rates may lead to higher metal concentrations in recycled plastic.
The global consumption of plastic continues to increase, and plastic recycling is highlighted as crucial for saving fossil resources and closing material loops. Plastic can be made from different polymers and contains a variety of substances, added intentionally to enhance the plastic’s properties (metals added as fillers, colourants, etc.). Moreover, plastic can be contaminated during use and subsequent waste management. Consequently, if substances and contaminants are not removed during recycling, potentially problematic substances might be recycled with the targeted polymers, hence the need for quantitative data about the nature and presence of these substances in plastic. Samples of selected polymers (PET, PE, PP, PS) were collected from different origins; plastic household waste, flakes/pellets of reprocessed plastic from households and industry, and virgin plastic. Fifteen selected metals (Al, As, Cd, Co, Cr, Cu, Fe, Hg, Li, Mn, Ni, Pb, Sb, Ti, Zn) were quantified and the statistical analysis showed that both the polymer and origin influenced the metal concentration. Sb and Zn were potentially related to the production stage of PET and PS, respectively. Household plastic samples (waste and reprocessed) were found to contain significantly higher Al, Pb, Ti and Zn concentrations when compared to virgin samples. Only the concentration of Mn was reduced during washing, suggesting that parts of it was present as physical contamination. While most of the metals were below legal limit values, elevated concentrations in reprocessed plastic from households, aligned with increasing recycling rates, may lead to higher metal concentrations in the future.
•Samples of waste, recycled and virgin plastics were obtained.•Majority of the samples contained phthalates.•Source of plastics significantly influenced the presence of phthalates.•Phthalates were ...not removed in recycling of household plastics.•DEHP could be used as indicator for monitoring phthalate contamination.
Plastics recycling has the potential to substitute virgin plastics partially as a source of raw materials in plastic product manufacturing. Plastic as a material may contain a variety of chemicals, some potentially hazardous. Phthalates, for instance, are a group of chemicals produced in large volumes and are commonly used as plasticisers in plastics manufacturing. Potential impacts on human health require restricted use in selected applications and a need for the closer monitoring of potential sources of human exposure. Although the presence of phthalates in a variety of plastics has been recognised, the influence of plastic recycling on phthalate content has been hypothesised but not well documented. In the present work we analysed selected phthalates (DMP, DEP, DPP, DiBP, DBP, BBzP, DEHP, DCHP and DnOP) in samples of waste plastics as well as recycled and virgin plastics. DBP, DiBP and DEHP had the highest frequency of detection in the samples analysed, with 360μg/g, 460μg/g and 2700μg/g as the maximum measured concentrations, respectively. Among other, statistical analysis of the analytical results suggested that phthalates were potentially added in the later stages of plastic product manufacturing (labelling, gluing, etc.) and were not removed following recycling of household waste plastics. Furthermore, DEHP was identified as a potential indicator for phthalate contamination of plastics. Close monitoring of plastics intended for phthalates-sensitive applications is recommended if recycled plastics are to be used as raw material in production.
•Technological, compositional, leaching and modelling uncertainties were included.•14 + 30 management scenarios assessed, all including parametrical uncertainty.•Two of the business-as-usual ...scenarios showed the lowest environmental impacts.
Air pollution control residues (APCr) are hazardous materials generated from municipal solid waste incineration and require appropriate management. This life cycle assessment (LCA) study investigates the environmental impacts of current and alternative management options, considering the possibility of a cascading management of APCr, where one treatment technology is followed by another. In total, 14 base case scenarios and 30 sensitivity scenarios were evaluated. The effects of APCr composition, leaching, time horizon, and uncertainties were investigated. The APCr management options with the lowest environmental impacts and the smallest uncertainties were i) backfilling of underground salt mines and ii) neutralization treatment followed by backfilling (Langøya, Norway). These options were followed by iii) scenarios that included Zn extraction, iv) cement stabilization of fresh APCr followed by landfilling and v) production of cement aggregates made from carbonated APCr followed by their utilization in construction works. Recovery of salts from APCr required further performance optimizations before being environmentally competitive with other options. Long-term leaching emissions of Zn, Cr and As were among the largest contributors to toxicity-related impacts, emphasizing the need for management strategies that minimize their leaching. The investigated scenarios demonstrate that increased “processing” and cascading utilization of the residues, contribute with increased uncertainty of the results compared to landfilling and may not necessarily lead to decreased environmental impacts. LCA studies of APCr management should address the full management chain, rather than just the first treatment. Overall, the results of this study were found robust, also considering potential changes in the surrounding energy system.
•LCA provides a much improved holistic view of waste management.•LCA helps understanding waste flows and potential environmental impacts.•There is still a need to use LCA models in integrated waste ...management.•LCA is expected to play a role in six areas of waste management in the future.
Life cycle assessment (LCA) has been used in waste management for the last two decades and hundreds of journal papers have been published. The use of LCA in waste management has provided a much-improved holistic view of waste management including waste flows and potential environmental impacts. Although much knowledge has been obtained from LCA studies, there is still a need to use LCA models in integrated waste management. This paper describes six areas where LCA is expected to play a role in waste management in the future: 1) understanding an existing waste management system; 2) improving existing waste management systems; 3) comparing alternative technologies/ technology performance; 4) technology development/prospective technologies; 5) policy development/strategic development; and 6) reporting. Illustrative examples are provided for each application area.
Purpose
Future scenarios and life cycle assessment (LCA) are powerful tools that can provide early sustainability assessments of novel products, technologies and systems. The combination of the two ...methods involves practical and conceptual challenges, but formal guidance and consensus on a rigorous approach are currently missing. This study provides a comprehensive overview of how different topic areas use future scenarios and LCA in order to identify useful methods and approaches, and to provide overall recommendations.
Methods
This study carried out a systematic literature review that involved searching for peer-reviewed articles on Web of Science, Scopus and Science Direct, utilising a rigorous set of keywords for future scenarios and for LCA. We identified 514 suitable peer-reviewed articles that were systematically analysed according to pre-defined sets of characteristics for the combined modelling of future scenarios and LCA.
Results and discussion
The numbers of studies combining future scenarios and LCA increase every year and in all of the 15 topic areas identified. This combination is highly complex, due to different sequences in the modelling between future scenarios and LCA, the use of additional models and topic area-specific challenges. We identify and classify studies according to three archetypal modelling sequences: input, output and hybrid. More than 100 studies provide methods and approaches for combining future scenarios and LCA, but existing recommendations are specific to topic areas and for modelling sequences, and consensus is still missing. The efficacy of many studies is hampered by lack of quality. Only half of the articles complied with the LCA ISO standards, and only one quarter demonstrated consistent knowledge of future scenario theory. We observed inconsistent use of terminology and a considerable lack of clarity in the descriptions of methodological choices, assumptions and time frames.
Conclusions and Recommendations
The combined use of future scenarios and LCA requires formal guidance, in order to increase clarity and communicability. Guidance should provide unambiguous definitions, identify minimum quality requirements and produce mandatory descriptions of modelling choices. The goal and scope of future scenarios and LCA should be in accordance, and quality should be ensured both for the future scenarios and the LCA. In particular, future scenarios should always be developed contextually, to ensure effective assessment of the problem at hand. Guidance should also allow for maintaining current modelling complexity and topic area differences. We provide recommendations from the reference literature on terminology, future scenario development and the combined use of future scenarios and LCA that may already constitute preliminary guidance in the field. Information collected and recommendations provided will assist in a more balanced development of the combined use of future scenarios and LCA in view of the urgent challenges of sustainable development.
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