Waste Management & Research: The Journal for a Sustainable Circular Economy

Waste electrical and electronic equipment is a complex waste stream and treatment options that work for one waste category or product may not be appropriate for others. A comprehensive case study has been performed for plastic-rich fractions that are treated in German dismantling centres. Plastics from TVs, monitors and printers and small household appliances have been characterised extensively. Based on the characterisation results, state-of-the-art treatment technologies have been combined to design an optimised recycling and upgrade process for each input fraction. High-impact polystyrene from TV casings that complies with the European directive on the restriction of hazardous substances (RoHS) was produced by applying continuous density separation with yields of about 60%. Valuable acrylonitrile butadiene styrene/polycarbonate can be extracted from monitor and printer casings by near-infrared-based sorting. Polyolefins and/or a halogen-free fraction of mixed styrenics can be sorted out by density separation from monitors and printers and small household appliances. Emerging separation technologies are discussed to improve recycling results.

Waste electrical and electronic equipment (WEEE) is one of the fastest growing waste streams worldwide with volumes increasing by 40% each year. WEEE has attracted increasing concern worldwide due to its high metal content and the potential environmental threat which results from uncontrolled recycling practices. Innovative physical separation techniques for WEEE recycling are preferential compared with chemical methods because of the reduction of energy and chemical consumption as well as potential environmental threats. Pneumatic jigging is a dry separation process capable of achieving good separation of coarse material within a very narrow density range, which makes it suitable as a pretreatment process for WEEE recycling. The work presented in this paper investigates the potential application of pneumatic jigging in metal recovery from WEEE. A pilot scale pneumatic jig has been developed by University of Nottingham Ningbo to separate shredded printed wiring boards into two streams: a light fraction (mainly non-metallic fraction consisting of glass fiber, fluffs, and plastic pieces) and dense fraction (metallic fraction). The novelty of work presented in this paper is the application of a dry separation technique in WEEE recycling for metal recovery. Compared with conventional wet separation processes involved in WEEE recycling industry, dry separation has the advantage of zero secondary pollution. The results of this experimental program show pneumatic jigging to be an effective and environmental friendly technique as a pretreatment process for the recovery of the metallic fraction from shredded WEEE.

The fine dust of incinerator bottom ash generated from dry discharge systems can be transformed into an inert material suitable for the production of hard, dense ceramics. Processing involves the addition of glass, ball milling and calcining to remove volatile components from the incinerator bottom ash. This transforms the major crystalline phases present in fine incinerator bottom ash dust from quartz (SiO₂), calcite (CaCO₃), gehlenite (Ca₂Al₂SiO₇) and hematite (Fe₂O₃), to the pyroxene group minerals diopside (CaMgSi₂O₆), clinoenstatite (MgSi₂O₆), wollastonite (CaSiO₃) together with some albite (NaAlSi₃O₈) and andradite (Ca₃Fe₂Si₃O₁₂). Processed powders show minimal leaching and can be pressed and sintered to form dense (>2.5 g cm^-3), hard ceramics that exhibit low firing shrinkage (<7%) and zero water absorption. The research demonstrates the potential to beneficially up-cycle the fine incinerator bottom ash dust from dry discharge technology into a raw material suitable for the production of ceramic tiles that have potential for use in a range of industrial applications.

A common assumption regarding the residual organic matter, in bottom ash, is that it does not represent a significant pool of organic carbon and, beyond metal-ion complexation process, it is of little consequence to evolution of ash/leachate chemistry. This article evaluates the effect of residual organic matter and associated microbial respiratory processes on leaching of toxic metals (i.e. arsenic, copper, chromium, molybdenum, nickel, lead, antimony and zinc), eco-toxicity of ash leachates. Microbial respiration was quantified with help of a respirometric test equipment OXITOP control system. The effect of microbial respiration on metal/residual organic matter leaching and eco-toxicity was quantified with the help of batch leaching tests and an eco-toxicity assay – Daphnia magna. In general, the microbial respiration process decreased the leachate pH and eco-toxicity, indicating modification of bioavailability of metal species. Furthermore, the leaching of critical metals, such as copper and chromium, decreased after the respiration in both ash types (fresh and weathered). It was concluded that microbial respiration, if harnessed properly, could enhance the stability of fresh bottom ash and may promote its reuse.

Studies on marine debris have gained worldwide attention since many types of debris have found their way into the food chain of higher organisms. Thus, it is crucial that more focus is given to this area in order to curb contaminations in sea food. This study was conducted to quantify plastic debris buried in sand at selected beaches in Malaysia. Marine debris was identified according to size range and distribution, and this information was related to preventive actions to improve marine waste issues. For the purpose of this study, comparison of plastic waste abundance between a recreational beach and fish-landing beaches was also carried out, since the different beach types represent different activities that produce debris. Six beaches along the Malaysian coastline were selected for this study. The plastic types in this study were related to the functions of the beach. While recreational beaches have abundant quantities of plastic film, foamed plastic including polystyrene, and plastic fragment, fish-landing beaches accumulated line and foamed plastic. A total of 2542 pieces (265.30 g m^-2) of small plastic debris were collected from all six beaches, with the highest number from Kuala Terengganu, at 879 items m^-2 on Seberang Takir Beach, followed by Batu Burok Beach with 780 items m^-2. Findings from studies of Malaysian beaches have provided a clearer understanding of the distribution of plastic debris. This demonstrates that commitments and actions, such as practices of the ‘reduce, reuse, recycle’ (3R) approach, supporting public awareness programmes and beach clean-up activities, are essential in order to reduce and prevent plastic debris pollution.

For the first time in Austria, fundamental technological and economic studies on recovering secondary raw materials from large landfills have been carried out, based on the ‘LAMIS – Landfill Mining Austria’ pilot project. A main focus of the research – and the subject of this article – was to develop an assessment or decision-making procedure that allows landfill owners to thoroughly examine the feasibility of a landfill mining project in advance. Currently there are no standard procedures that would sufficiently cover all the multiple-criteria requirements. The basic structure of the multiple attribute decision making process was used to narrow down on selection, conceptual design and assessment of suitable procedures. Along with a breakdown into preliminary and main assessment, the entire foundation required was created, such as definitions of requirements to an assessment method, selection and accurate description of the various assessment criteria and classification of the target system for the present ‘landfill mining’ vs. ‘retaining the landfill in after-care’ decision-making problem. Based on these studies, cost-utility analysis and the analytical-hierarchy process were selected from the range of multiple attribute decision-making procedures and examined in detail. Overall, both methods have their pros and cons with regard to their use for assessing landfill mining projects. Merging these methods or connecting them with single-criteria decision-making methods (like the net present value method) may turn out to be reasonable and constitute an appropriate assessment method.

A life cycle assessment was carried out to evaluate the effects of two packaging waste prevention activities on the overall environmental performance of the integrated municipal waste management system of Lombardia region, Italy. The activities are the use of refined tap water instead of bottled water for household consumption and the substitution of liquid detergents packaged in single-use containers by those distributed ‘loose’ through self-dispensing systems and refillable containers. A 2020 baseline scenario without waste prevention is compared with different waste prevention scenarios, where the two activities are either separately or contemporaneously implemented, by assuming a complete substitution of the traditional product(s). The results show that, when the prevention activities are carried out effectively, a reduction in total waste generation ranging from 0.14% to 0.66% is achieved, corresponding to a 1–4% reduction of the affected packaging waste fractions (plastics and glass). However, the improvements in the overall environmental performance of the waste management system can be far higher, especially when bottled water is substituted. In this case, a nearly 0.5% reduction of the total waste involves improvements ranging mostly between 5 and 23%. Conversely, for the substitution of single-use packaged liquid detergents (0.14% reduction of the total waste), the achieved improvements do not exceed 3% for nearly all impact categories.