Impact of thermal soil treatment on heavy metal mobility in the context of waste management.

Thermal soil treatment is a well-established remediation method to remove organic contaminants from soils in waste management. The co-contamination with heavy metals raises the question if thermal soil treatment affects heavy metal mobility in soils. In this study, four contaminated soils and a reference sample were subjected to thermal treatment at 105°C, 300°C and 500°C for 7 day. Thermogravimetry and differential scanning calorimetry were used to understand the reactions, and resulting gases were identified by Fourier-transformed infrared spectroscopy. Treated and untreated samples were characterised by X-ray diffraction (XRD) and electron microprobe analysis and subjected to pH-dependent leaching tests, untreated samples additionally by X-ray-fluorescence (XRF) and inductively coupled plasma mass spectroscopy (ICP-MS). Leachates were analysed using ICP-MS and ion chromatography. Maximum available concentrations were used for hydrogeochemical modelling using LeachXS/Orchestra to predict leaching control mechanisms. Leaching experiments show that thermal treatment tends to decrease the mobility at alkaline pH of Pb, Zn, Cd, As and Cu, but to increase the mobility of Cr. In the acidic to neutral pH range, no clear trend is visible. Hydrogeochemical modelling suggests that adsorption processes play a key role in controlling leaching. It is suggested that the formation of minerals with a more negatively charged surface during thermal treatment are one reason why cations such as Pb2+, Zn2+, Cd2+ and Cu2+ are less mobile after treatment. Future research should focus on a more comprehensive mineralogical investigation of a larger number of samples, using higher resolution techniques such as nanoscale secondary ion mass spectrometry to identify surface phases formed during thermal treatment and/or leaching.

Feasibility Study for Finding Mathematical Approaches to Describe the Optimal Operation Point of Sensor-Based Sorting Machines for Plastic Waste.

At present, sensor-based sorting machines are usually not operated at the optimal operation point but are either overrun or underrun depending on the availability of waste streams. Mathematical approaches for predefined ideal mixtures can be found based on the input stream composition and the throughput rate. This scientific article compares whether and under what conditions these approaches can be applied to sensor-based sorting machines. Existing data for predefined ideal mixtures are compared with newly generated data of real waste on three sensor-based sorting setups in order to make significant statements. Five samples of 3D plastics at regular intervals were taken in a processing plant for refuse-derived fuels. With the comparison of all these results, four hypotheses were validated, related to whether the same mathematical approaches can be transferred from ideal mixtures to real waste and whether they can be transferred to sensor-based sorting machines individually or depending on the construction type. The developed mathematical approaches are regression models for finding the optimal operation point to achieve a specific sensor-based sorting result in terms of purity and recovery. For a plant operator, the main benefit of the findings of this scientific article is that purity could be increased by 20% without substantially adapting the sorting plant.

Selective delamination by milling as a first step in the recycling of photovoltaic modules.

The recycling of photovoltaic modules has been a topic of increasing interest over the last years. At industrial scale, delamination of the module structure, which represents the first step in the recycling process, is currently achieved by multi-stage crushing. However, the quality of the outputs obtained through subsequent processing is low and offers room for improvement. Milling was investigated as an alternative physical delamination method. Lab-scale experiments were conducted to evaluate the applicability of the technology in general, as well as comparing a process by which all non-glass layers are removed at the same time (one-step) with one where the backsheet is removed as a separate fraction (two-step). Furthermore, a qualitative and quantitative analysis of the resulting outputs in each case was performed. Results show effective delamination by the milling process. Advantages in comparison to the currently used delamination techniques are identified in regard to the quality of the recovered glass, which is separated directly during delamination as well as the fact that the subsequent processing can therefore be focused on the polymers, metals and silicon contained within the removed materials. Some possibly problematic aspects in regard to upscaling have also been identified and discussed. While the two-step process enables the recovery of more homogenous outputs, it is also associated with a higher effort regarding input characterization and the milling process itself. In order to reach a conclusion about which process option is more feasible, additional investigations concerning the milling process, the input material and the output fractions are needed.

Thermal delamination of end-of-life crystalline silicon photovoltaic modules.

Thermal delamination - meaning the removal of polymers from the module structure by a thermal process - as a first step in the recycling of crystalline silicon (c-Si) photovoltaic (PV) modules in order to enable the subsequent recovery of secondary raw materials was investigated. A correlation between treatment temperature and duration was established by an iterative process. Furthermore, chemical characterization of the resulting solid outputs (glass, cell, ribbons and residues) was performed in order to assess their further processing options. Additionally, the effect of removing the backsheet as a pre-treatment before the actual delamination process was investigated in relation to the aforementioned aspects of treatment duration and output quality. Results show that increased temperatures reduce the necessary treatment duration (65 minutes at 500°C, 33 minutes at 600°C) while generating the same output quality. The backsheet removal leads to an additional duration decrease of more than 45% at each considered temperature, while also having positive effects relating to fewer solid residues and easier flue gas handling. In regard to the main output specifications no significant influence of the pre-treatment is observed. Overall thermal delamination can be seen as a feasible method in order to obtain high value secondary raw materials from c-Si PV modules, while backsheet removal as pre-treatment should be considered as advantageous from multiple standpoints.

Recycling chains for lithium-ion batteries: A critical examination of current challenges, opportunities and process dependencies.

Lithium-ion batteries (LIBs) show high energy densities and are therefore used in a wide range of applications: from portable electronics to stationary energy storage systems and traction batteries used for e-mobility. Considering the projected increase in global demand for this energy storage technology, driven primarily by growth in e-vehicles, and looking at the criticality of some raw materials used in LIBs, the need for an efficient recycling strategy emerges. In this study, current state-of-the-art technologies for LIB recycling are reviewed and future opportunities and challenges, in particular to recover critical raw materials such as lithium or cobalt, are derived. Special attention is paid to the interrelationships between mechanical or thermal pre-treatment and hydro- or pyrometallurgical post-treatment processes. Thus, the unique approach of the article is to link processes beyond individual stages within the recycling chain. It was shown that influencing the physicochemical properties of intermediate products can lead to reduced recycling rates or even the exclusion of certain process options at the end of the recycling chain. More efforts are needed to improve information and data sharing on the exact composition of feedstock for recycling as well as on the processing history of intermediates to enable closed loop LIB recycling. The technical understanding of the interrelationships between different process combinations, such as pyrolytic or mechanical pre-treatment for LIB deactivation and metal separation, respectively, followed by hydrometallurgical treatment, is of crucial importance to increase recovery rates of cathodic metals such as cobalt, nickel, and lithium, but also of other battery components.

The fire risk of portable batteries in their end-of-life: Investigation of the state of charge of waste lithium-ion batteries in Austria.

The increased utilisation of lithium-ion batteries in the last years does not come without cost. Due to thermal runaway and exothermic degradation reactions, portable batteries pose enormous risks to waste management systems and infrastructure in their end-of-life phase. All over Europe, the number of waste fires caused by lithium-ion batteries are rising. The risk of a battery fire is mainly influenced by the probability and severity of a thermal runaway or exothermic degradation, which depends on the current state of charge (SOC) of the respective battery. In order to determine the distribution of the SOC which is one of the main influence factors to waste fires caused by lithium-ion batteries, 980 waste battery cells were representatively sampled, manually dismantled and analysed using a prototypic laboratory test stand. Approximately 24% of the analysed cells and batteries had a residual SOC of at least 25%, and approximately 12% had a residual SOC of at least 50%. Hence, approximately every fourth to eighth portable battery threatens to cause a waste fire when critically damaged. Furthermore, a distinct relationship between the actual cell voltage and the residual SOC was found for end-of-life portable batteries.

[System Concept of Production Design and Development in Scrap and Metal Recycling]. / Die sieben Kerneinflussfaktoren auf die Weiterentwicklung von Produktionsanlagen im Schrottrecycling.

The present system concept of metal and scrap recycling plants deals with possible effects of renewed legislative amendments and evaluates legal and technological as well as economical aspects of the value stream oriented shredder process. It is a system oriented approach to point out the main influencing factors on the development of shredder plants in scrap and metal recycling. Those factors are being merged into a superordinate system concept used to support strategic management decisions regarding future investments in the waste treatment sector.Under the given legal circumstances, the shredder process itself has to be resource-friendly, energy- and cost-efficient while still following the stated emission limit values.Therefore, the conceptual focus lies in the argumentation and evaluation of technical challenges as a major result of the implementation of national and international legal terms in the age of volatile market conditions, present recession, and value decline in prematerial compositions. The system concept is the result of a research project from October 2016 to December 2019 at the TSR Recycling GmbH & Co. KG, Lünen, Germany.The concept itself forms a base for the development of plant technology in other metal recycling fields, such as e­waste recycling. Due to the current COVID-19 pandemic situation, the model is extended to other and further influencing factors and helps to understand the short lifespan of theoretical modelling within the field of scrap metal recycling.

Processability of Different Polymer Fractions Recovered from Mixed Wastes and Determination of Material Properties for Recycling.

To achieve future recycling targets and CO2 and waste reduction, the transfer of plastic contained in mixed waste from thermal recovery to mechanical recycling is a promising option. This requires extensive knowledge of the necessary processing depth of mixed wastes to enrich plastics and their processability in polymer processing machines. Also, the selection of a suitable processing method and product application area requires appropriate material behaviour. This paper investigates these aspects for a commercial processed, mixed waste, and two different mixed polyolefin fractions. The wastes are processed at different depths (e.g., washed/not washed, sorted into polyethylene, polypropylene, polyethylene terephthalate, polystyrene/unsorted) and then either homogenised in the extruder in advance or processed heterogeneously in the compression moulding process into plates. The produced recyclates in plate form are then subjected to mechanical, thermal, and rheological characterisation. Most investigated materials could be processed with simple compression moulding. The results show that an upstream washing process improves the achievable material properties, but homogenisation does not necessarily lead to an improvement. It was also found that a higher treatment depth (recovery of plastic types) is not necessary. The investigations show that plastic waste recovery with simple treatment from mixed, contaminated wastes into at least downcycling products is possible.

Influence of material alterations and machine impairment on throughput related sensor-based sorting performance.

Experiments with sensor-based sorting (SBS) machinery provide insight into the effect of throughput rate and input composition on the sorting performance. For this purpose, material mixtures with certain compositions and particle size distributions were created from waste fractions and sorted at various throughput rates. To evaluate the sorting performance of the SBS unit (using near infrared technology) in dependence of the applied load, four assessment factors concerning the output fractions were studied: yield, product purity, recovery/product quantity and incorrectly discharged share of reject particles. The influences on the assessment parameters of light twodimensional (2D) particles in the input of a sorting stage and failing air valves in an SBS unit were evaluated for various input compositions at different throughput rates. It was found that a share of approximately 5 wt% 2D particles in the input had a similar negative effect on the yield as the malfunction of 20% of all air valves in an SBS machine at high throughput rates. Additionally, the failure of the air valves reduced the product purity of the sorting stage at increased throughput rates. Furthermore, qualitative observations concerning systematic effects of prior studies could be confirmed. Resulting graphs for a specific input composition of an SBS unit at varying throughput rates could be used to adjust the throughput rate to meet the exact demands for a sorting stage.

Characterisation and material flow analysis of end-of-life portable batteries and lithium-based batteries in different waste streams in Austria.

Although separate collection systems for portable batteries (PBs) have been installed years ago, high amounts of batteries still do not enter the collection systems of the member states of the European Union (EU). In Austria, the collection rate has recently dropped to the EU target value of 45%. For the purposes of this study, a comprehensive survey was conducted to identify the destinations of the other end-of-life batteries. A literature survey and an assessment of different waste streams (WSs) were followed by sampling and sorting campaigns for highly relevant WSs (residual waste, lightweight packaging waste, metal packaging waste, and small waste electrical and electronic equipment). The results underwent material flow analysis, showing that more than 800 metric tonnes of portable batteries are misplaced into non-battery-specific collection systems, 718 metric tonnes of them entering residual waste collection. Considerable amounts of batteries are stockpiled, stored or hoarded in Austrian households. Lithium-based batteries, representing a serious risk of fire to the waste industry and making up for 30% of the marketed amount, are still scarcely arriving in waste management systems.

Methods for identifying the material-recyclable share of SRF during co-processing in the cement industry.

Solid Recovered Fuels (SRF) include non-combustible mineral components (e.g. CaCO3, SiO2, Al2O3) that are required as raw materials for producing clinker and are completely incorporated into the clinker during the thermal recovery of SRF. This paper discusses simple and practicable ways of finding the relative amount of SRF that may be utilised as raw material (given as the recycling index). For this purpose, the entire mineral content of SRF was determined as the ash content and its main components were identified using different analytical methods.•A fusion melt of the previously incinerated sample with subsequent measuring using ICP-OES and XRF as well as a total digestion of the incinerated and non-incinerated sample with subsequent measuring using ICP-OES/ICP-MS were applied.•The results showed a good agreement of all four analytical methods for the elementary oxides Al2O3, CaO, Fe2O3, SiO2, TiO2, P2O5 and MgO (relative deviation from 6.6 to 38.9%) and slightly higher deviations for K2O, Na2O and SO3 (14.2-96.0%).•It was also shown that different incineration temperatures (550 °C, 815 °C and 950 °C) have no effect on the result of the recycling index unless it is assumed that the recycling index equals the ash content.

Effects of cement addition and briquetting of rock wool on its geomechanical stability in landfills.

Landfilling of mineral wool waste in big bags at separate landfill compartments is required in Austria. This results in enormous differences in the Young's moduli between common construction and demolition (C&D) waste compartments and mineral wool compartments, which causes severe accidents in terms of overturned vehicles due to sudden subsidence of the subsurface. Conditioning of mineral wool waste might be applied to adjust its geomechanical behaviour to that of common C&D waste but has never been investigated scientifically before. In this study we compare three scenarios for the conditioning of rock wool for landfilling: (A) loosely packing, (B) cutting comminution + cement addition and (C) cutting comminution + cement-supported briquetting. The performance of the different sample bodies under landfill conditions was simulated at the lab scale by cyclic loading (1223-3112 N, up to 160 cycles) using a 'Wille Geotechnik UL 300' press. The deformation was monitored during the experiment and Young's modulus was derived graphically, whereas the test execution was piston controlled. The Young's modulus increased during the experiments from 0.2 MPa to 4.6 MPa for scenario (A), from 0.6 MPa to 20.5 MPa for scenario (B) and from 7.5 MPa to 111.0 MPa for scenario (C). These results show that a combination of comminution and cement-supported briquetting significantly increases the geotechnical performance of mineral wool waste with respect to landfilling, which is still three orders of magnitude below that of common C&D waste, which is in the range of 30,000 MPa.

X-ray fluorescence sorting of non-ferrous metal fractions from municipal solid waste incineration bottom ash processing depending on particle surface properties.

A heavy non-ferrous metal fraction (< 50 mm) of municipal solid waste incineration bottom ashes from wet-mechanical treatment was separated by screening, magnetic separation and eddy-current separation into ferrous metals, non-ferrous metals and residual sub-fractions. The non-ferrous metal fractions were divided and subjected to (i) a washing process, (ii) dry abrasion and (iii) no mechanical pre-treatment to study the effect of resulting different surface properties on a subsequent X-ray fluorescence sorting into precious metals, zinc, copper, brass, stainless steel and a residual fraction. The qualities of the X-ray fluorescence output fractions were investigated by chemical analyses (precious metal fraction and the residual fraction), pyrometallurgical tests and subsequent chemical analyses of the metals and slags produced by the melting processes (zinc, copper, brass and stainless steel fraction). Screening directs brass and stainless steel primarily into the coarser fractions, while copper and residual elements were rather transferred into the finer fractions. X-ray fluorescence sorting yielded zinc, copper, brass, stainless steel and precious metals fractions in marketable qualities. Neither a negative nor a positive impact of mechanical pre-treatment on the composition of these fractions was identified. Solely the yield of the brass fraction in the grain size 16-20 mm decreased with increasing mechanical pre-treatment. The pre-treatment also had no impact on yield and quality of the products of pyrometallurgical tests.

Influence of surface roughness and surface moisture of plastics on sensor-based sorting in the near infrared range.

In the project 'NEW-MINE' the use of sensor-based sorting machinery in the field of 'landfill mining' is investigated. Defilements pose a particular challenge in the treatment and sorting of plastics contained in landfills. For this reason, the effects of various pollutants caused by the interactions in the landfill body or the mechanical treatment steps in landfill mining are examined. In the following elaboration, the focus is on the influences of surface moisture and surface roughness of plastics on sensor-based sorting by means of near-infrared technology. Near-infrared radiation (NIR) in a wavelength range of 990 nm to 1500 nm has been used for the detection and classification of plastic particles. The experiments demonstrate that increased surface roughness reduces signal noise and thereby improves the classification of both spectrally similar and transparent plastics, but reduces the yield of low-softening plastics because their sliding speed on a sensor-based chute sorter varies as a result of the heating of the chute. Surface moisture causes the absorption of radiation from 1115 nm (high density polyethylene [HDPE], linear low density polyethylene [LLDPE], polyethylen terephthalate [PET] and polyvinylchloride [PVC]) or from 1230 nm (low density polyethylene [LDPE], polypropylene [PP] and thermoplastic polyurethane [TPU]) up to at least 1680 nm, which causes amplification or attenuation of various extremes in the derivative. However, the influence of surface moisture on the yield of plastics is usually very low and depends on the spectral differences between the different plastics.

Output-oriented analysis of the wet mechanical processing of polyolefin-rich waste for feedstock recycling.

In recent years, an increasing number of studies have revealed that plastics and their components (e.g. plasticisers) pose an environmental risk. However, it is hard to imagine how our industrialised society could do without these materials, since the fields of application are manifold. One possible approach to tackle this mounting problem is the implementation of a comprehensive and well-functioning collection and recycling system. An international comparison shows that only a small proportion of the total plastics in circulation is collected and recycled. The investigations conducted under the present research project, 'Plastic Reborn', focused on both identification and analysis of the discharge paths of polyolefin-rich waste streams, under the Austrian waste management system. Another objective was determining the utilisation potential of the output fractions of these polyolefin-rich waste streams, generated from a wet mechanical processing pilot plant. Experiments have shown that the polyolefins are successfully separated from the waste streams and that a total polyolefin potential of 429,000 t y-1 remains unexploited in the Austrian waste management system. Thus, these separated plastic fractions can make a significant contribution to the implementation of the European Circular Economy Directive. The residual fractions meet the legal and company-specific requirements for their use as solid recovered fuels in co-combustion plants.

Case study: Is the 'catch-all-plastics bin' useful in unlocking the hidden resource potential in the residual waste collection system?

Austria's performance in the collection of separated waste is adequate. However, the residual waste still contains substantial amounts of recyclable materials - for example, plastics, paper and board, glass and composite packaging. Plastics (lightweight packaging and similar non-packaging materials) are detected at an average mass content of 13% in residual waste. Despite this huge potential, only 3% of the total amount of residual waste (1,687,000 t y-1) is recycled. This implies that most of the recyclable materials contained in the residual waste are destined for thermal recovery and are lost for recycling. This pilot project, commissioned by the Land of Lower Austria, applied a holistic approach, unique in Europe, to the Lower Austrian waste management system. It aims to transfer excess quantities of plastic packaging and non-packaging recyclables from the residual waste system to the separately collected waste system by introducing a so-called 'catch-all-plastics bin'. A quantity flow model was constructed and the results showed a realistic increase in the amount of plastics collected of 33.9 wt%. This equals a calculated excess quantity of 19,638 t y-1. The increased plastics collection resulted in a positive impact on the climate footprint (CO2 equivalent) in line with the targets of EU Directive 94/62/EG (Circular Economy Package) and its Amendments. The new collection system involves only moderate additional costs.

Landfill mining: Developing a comprehensive assessment method.

In Austria, the first basic technological and economic examinations of mass-waste landfills with the purpose to recover secondary raw materials have been carried out by the 'LAMIS - Landfill Mining Österreich' pilot project. A main focus of its research, and the subject of this article, is the first conceptual design of a comprehensive assessment method for landfill mining plans, including not only monetary factors (like costs and proceeds) but also non-monetary ones, such as the concerns of adjoining owners or the environmental impact. Detailed reviews of references, the identification of influences and system boundaries to be included in planning landfill mining, several expert workshops and talks with landfill operators have been performed followed by a division of the whole assessment method into preliminary and main assessment. Preliminary assessment is carried out with a questionnaire to rate juridical feasibility, the risk and the expenditure of a landfill mining project. The results of this questionnaire are compiled in a portfolio chart that is used to recommend, or not, further assessment. If a detailed main assessment is recommended, defined economic criteria are rated by net present value calculations, while ecological and socio-economic criteria are examined in a utility analysis and then transferred into a utility-net present value chart. If this chart does not support making a definite statement on the feasibility of the project, the results must be further examined in a cost-effectiveness analysis. Here, the benefit of the particular landfill mining project per capital unit (utility-net present value ratio) is determined to make a final distinct statement on the general benefit of a landfill mining project.

Holistic assessment of a landfill mining pilot project in Austria: Methodology and application.

Basic technical and economic examinations of Austrian mass waste landfills, concerning the recovery of secondary raw materials, have been carried out by the 'LAMIS - Landfill Mining Austria' pilot project for the first time in Austria. A main focus of the research - the subject of this article - was the first devotion of a pilot landfill to an integrated ecological and economic assessment so that its feasibility could be verified before a landfill mining project commenced. A Styrian mass waste landfill had been chosen for this purpose that had been put into operation in 1979 and received mechanically-biologically pre-treated municipal waste till 2012. The whole assessment procedure was divided into preliminary and main assessment phases to evaluate the general suitability of a landfill mining project with little financial and human resource expense. A portfolio chart, based on a questionnaire, was created for the preliminary assessment that, as a result, has provided a recommendation for subsequent investigation - the main assessment phase. In this case, specific economic criteria were assessed by net present value calculation, while ecological or socio-economic criteria were rated by utility analysis, transferring the result into a utility-net present value chart. In the case of the examined pilot landfill, assessing the landfill mining project produced a higher utility but a lower net present value than a landfill leaving-in for aftercare. Since no clearly preferable scenario could be identified this way, a cost-revenue analysis was carried out in addition that determined a dimensionless ratio: the 'utility - net present value quotient' of both scenarios. Comparing this quotient showed unmistakably that in the overall assessment, 'leaving the landfill in aftercare' was preferable to a 'landfill mining project' in that specific case.

Landfill mining: Development of a cost simulation model.

Landfill mining permits recovering secondary raw materials from landfills. Whether this purpose is economically feasible, however, is a matter of various aspects. One is the amount of recoverable secondary raw material (like metals) that can be exploited with a profit. Other influences are the costs for excavation, for processing the waste at the landfill site and for paying charges on the secondary disposal of waste. Depending on the objectives of a landfill mining project (like the recovery of a ferrous and/or a calorific fraction) these expenses and revenues are difficult to assess in advance. This situation complicates any previous assessment of the economic feasibility and is the reason why many landfills that might be suitable for landfill mining are continuingly operated as active landfills, generating aftercare costs and leaving potential hazards to later generations. This article presents a newly developed simulation model for landfill mining projects. It permits identifying the quantities and qualities of output flows that can be recovered by mining and by mobile on-site processing of the waste based on treatment equipment selected by the landfill operator. Thus, charges for disposal and expected revenues from secondary raw materials can be assessed. Furthermore, investment, personnel, operation, servicing and insurance costs are assessed and displayed, based on the selected mobile processing procedure and its throughput, among other things. For clarity, the simulation model is described in this article using the example of a real Austrian sanitary landfill.

Solid recovered fuels in the cement industry--semi-automated sample preparation unit as a means for facilitated practical application.

One of the challenges for the cement industry is the quality assurance of alternative fuel (e.g., solid recovered fuel, SRF) in co-incineration plants--especially for inhomogeneous alternative fuels with large particle sizes (d95⩾100 mm), which will gain even more importance in the substitution of conventional fuels due to low production costs. Existing standards for sampling and sample preparation do not cover the challenges resulting from these kinds of materials. A possible approach to ensure quality monitoring is shown in the present contribution. For this, a specially manufactured, automated comminution and sample divider device was installed at a cement plant in Rohoznik. In order to prove its practical suitability with methods according to current standards, the sampling and sample preparation process were validated for alternative fuel with a grain size >30 mm (i.e., d95=approximately 100 mm), so-called 'Hotdisc SRF'. Therefore, series of samples were taken and analysed. A comparison of the analysis results with the yearly average values obtained through a reference investigation route showed good accordance. Further investigations during the validation process also showed that segregation or enrichment of material throughout the comminution plant does not occur. The results also demonstrate that compliance with legal standards regarding the minimum sample amount is not sufficient for inhomogeneous and coarse particle size alternative fuels. Instead, higher sample amounts after the first particle size reduction step are strongly recommended in order to gain a representative laboratory sample.