E-waste Stream Research Articles

E-waste challenges of generative artificial intelligence.

Generative artificial intelligence (GAI) requires substantial computational resources for model training and inference, but the electronic-waste (e-waste) implications of GAI and its management strategies remain underexplored. Here we introduce a computational power-driven material flow analysis framework to quantify and explore ways of managing the e-waste generated by GAI, with a particular focus on large language models. Our findings indicate that this e-waste stream could increase, potentially reaching a total accumulation of 1.2-5.0 million tons during 2020-2030, under different future GAI development settings. This may be intensified in the context of geopolitical restrictions on semiconductor imports and the rapid server turnover for operational cost savings. Meanwhile, we show that the implementation of circular economy strategies along the GAI value chain could reduce e-waste generation by 16-86%. This underscores the importance of proactive e-waste management in the face of advancing GAI technologies.

Source identification and human exposure assessment of organophosphate flame retardants and plasticisers in soil and outdoor dust from Nigerian e-waste dismantling and dumpsites

Electronic waste (e-waste) dismantling and dumpsite processes are major sources of organophosphate flame retardant and plasticiser emissions and may pose potentially adverse effects on environment and human health. In 20 outdoor dust and 49 soil samples collected from four e-waste dismantling and three e-waste dumpsites in two States of Nigeria (Lagos and Ogun), we identified 13 alternative plasticisers (APs), 7 legacy phthalate plasticisers (LPs), and 17 organophosphorus flame retardants (OPFRs) for the first time in African e-waste streams. In the samples from dismantling sites, the range (median) concentrations of ∑13APs, ∑7LPs, and ∑17OPFRs were 11 to 2747 μg/g (144 μg/g), 11 to 396 μg/g (125 μg/g), and 0.2 to 68 μg/g (5.5 μg), in dust respectively and 1.8 to 297 μg/g (55 μg/g), 1.3 to 274 μg/g (48.5 μg/g), and 1.6 to 62 μg/g (1.6 μg/g), in soil respectively. Results for soil samples from e-waste dumpsites were (6.6 to 195 μg/g (23.7 μg/g), 6.0 to 295 μg/g (54.8), and 0.4 to 42.3 μg/g (9.0 μg/g) for ∑13APs, ∑7LPs, and ∑17OPFRs respectively. Overall, concentrations of APs were significantly higher at the dismantling sites (p = 0.005) compared to dumpsites, levels of LPs were higher at dismantling sites but not significant, while OPFR concentrations were significantly higher in dumpsite samples (p = 0.005). Plasticisers were found to be major contributors to pollution at e-waste dismantling sites, while OPFRs were associated with both automobile dismantling and e-waste dumpsite processes. Following particle size fractionation of selected soil samples, higher concentrations of targeted compounds were observed in the smaller mesh (180 μm) soil sieve fraction. For dust, the total median estimated daily intake via ingestion and dermal adsorption (EDIing and EDIderm) ranged from 43 to 74 ng/kg bw/day and 0.4 to 0.7 ng/kg bw/day, respectively. Correspondingly, 4.6 to 45 ng/kg bw/day and 0.015 to 0.57 ng/kg bw/day were the values found for soil, respectively. According to these results, the targeted chemicals do not appear to pose a non-carcinogenic risk to e-waste workers through ingestion or dermal contact of bio-accessible fractions of the chemicals. Human biomonitoring campaigns are recommended in the Nigerian e-waste environment considering the elevated concentration levels found for the majority of targeted compounds and that risk parameters required for exposure assessment were only available for a limited number of compounds.

Development of complete hydrometallurgical processes for gold recovery from ICs and CPUs using ionic liquids

Integrated circuits (ICs) and central processing units (CPUs), essential components of electrical and electronic equipment (EEE), are complex composite materials rich in recyclable high-value strategic and critical metals, with many in concentrations higher than in their natural ores. With gold the most valuable metal present, increase in demand for gold for EEE and its limited availability have led to a steep rise in the market price of gold, making gold recycling a high priority to meet demand. To overcome the limitations associated with conventional technologies for recycling e-waste, the use of greener technologies (ionic liquids (ILs) as leaching agents), offers greater potential for the recovery of gold from e-waste components. While previous studies have demonstrated the efficiency and feasibility of using ILs for gold recovery, these works predominantly concentrate on the extraction stage and often utilise simulated solutions, lacking the implementation of a complete process validated with real samples to effectively assess its overall effectiveness. In this work, a simulated Model Test System was used to determine the optimal leaching and extraction conditions before application to real samples. With copper being the most abundant metal in the e-waste fractions, to access the gold necessitated a two-stage pre-treatment (nitric acid leaching followed by aqua regia leaching) to ensure complete removal of copper and deliver a gold-enriched leach liquor. Gold extraction from the leach liquor was achieved by liquid-liquid extraction using Cyphos 101 (0.1 M in toluene with an O:A = 1:1, 20 °C, 150 rpm, and 15 min) and as a second process by sorption extraction with loaded resins (Amberlite XAD-7 with 300 mg of Cyphos 101/g of resins at 20 °C, 150 rpm and 3 h). In both processes, complete stripping and desorption of gold was achieved (0.5 M thiourea in 0.5 M HCl) and gold recovered, as nanoparticles of purity ≥95%, via a reduction step using a sodium borohydride solution (0.1 M NaBH4 in 0.1 M NaOH). These two hydrometallurgical processes developed can achieve overall efficiencies of ≥95% for gold recovery from real e-waste components, permit the reuse of the IL and resins up to five consecutive times, and offer a promising approach for recovery from any e-waste stream rich in gold.

Evaluation of Metals in Printed Wiring Boards of Selected Discarded Mobile Phones in Nigeria

Obsolete mobile phones form a major component of the e-waste stream. The Printed wiring boards (PWBs) of mobile phones are packed with economic and toxic metals. Regulatory bodies such as Restriction of Hazardous Substances (RoHS) directives regulate the amount of these toxic metals in electrical and electronic equipment. This study is aimed at evaluating selected critical metals present in PWBs of three popular brands of discarded mobile phones used in Nigeria to understudy the behaviour of original equipment manufacturers (OEMs) regarding toxicity, economic potentials, and level of compliance with international initiatives by regulatory bodies to reduce the level of toxic metals in electronic equipment. PWBs obtained from 60 discarded mobile phones of 3 popular mobile phone brands used in Nigeria were chopped into smaller particles, extracted according to EPA 3050B method, and analysed using the Inductive Coupled Plasma-Optical Emission Spectrometry technique. It was observed that Mn, Fe, Zn, and Cu, had the highest concentration range across all brands studied. Notable toxic metals such as Pb, Cd, Cr, and As have mean and standard deviation values of 0.43±0.38 mg/kg, 0.62±0.160 mg/kg, 5.16±1.06 mg/kg, and 84.97±13.83 mg/kg respectively. Economic metals: Cu, Ag, and Au had mean and standard deviation values of 80.37±16.89 mg/kg, 2.12±0.43 mg/kg, and 0.95±0.19 mg/kg respectively. Results from the study indicate that PWBs of mobile phones are a perfect secondary source of a large variety of metals vital for the recycling industry. Also, the low levels of toxic metals suggest that some OEMs are already adopting the 'design-for-environment' option. Therefore, PWBs studied seem eco-friendly; however, need to be handled with care as there are still some toxic metals of concern not determined in this study.

Exploring the insights and benefits of biomass-derived sulfuric acid activated carbon for selective recovery of gold from simulated waste streams

The surging affluent in society, concomitant with increasing global demand for electrical and electronic devices, has led to a sharp rise in e-waste generation. E-wastes contain significant amounts of precious metals, such as gold, which can be recovered and reused, thus reducing the environmental impact of mining new metals. Selective recovery using sustainable and cost-effective materials and methods is therefore vital. This study undertook a detailed evaluation of low-cost biomass-derived activated carbon (AC) for selective recovery of Au from simulated e-waste streams. Utilizing high-performance synthesized H2SO4-AC, the adsorption mechanisms were explicated through a combination of characterization techniques, i.e., FE-SEM, BET, TGA, XRD, FTIR, XPS, and DFT simulations to conceptualize the atomic and molecular level interactions. Optimization of coordination geometries between model H2SO4-AC and anionic complexes revealed the most stable coordination for AuCl4- (binding energy, Eb = -4064.15 eV). The Au selectivity was further enhanced by reduction of Au(III) to Au(0), as determined by XRD and XPS. The adsorption reaction was relatively fast (∼5h), and maximum Au uptake reached 1679.74 ± 37.66 mg/g (among highest), achieved through adsorption isotherm experiments. Furthermore, a mixture of 0.5 M thiourea/1 M HCl could effectively elute the loaded Au and regenerate the spent AC. This study presents radical attempts to examine in detail, the synergistic effects of H2SO4 activation on biomass-derived ACs for selective recovery of Au from complex mixtures. The paper therefore describes a novel approach for the selective recovery of Au from e-wastes using multifunctional biomass-derived H2SO4-AC.

Exploring microbial adaptation of immobilised acidophilic cultures to improve microbial oxidation rates and copper tolerance in e-waste bioleaching

The rate of ferric iron regeneration by microbial oxidation is the rate determining step in the bioleaching of printed circuit boards (PCBs). Therefore, improvement of the volumetric rate of ferric iron formation is key for the overall bioleaching efficiency. The volumetric rate is impacted by both the specific rate and the biomass concentration. Limiting the exposure of the bioleaching microorganisms to accumulated toxic metal ions in solution, as well as the presence of inhibiting material components in PCBs through biofilm formation and immobilisation, as well as their adaptation to these inhibitors, is proposed to mitigate against decrease in specific rate while biomass retention by immobilisation is expected to positively impact volumetric rate. In this study, a mixed mesophilic culture, consisting of Leptospirillum (L.) ferriphilum, Acidithiobacillus (At.) caldus, Acidiplasma (Ap.) cupricumulans as dominant species was immobilised on polyurethane foam (PUF) and adapted to 6.0 g/L Cu2+. The rate of microbial ferrous iron oxidation by the immobilised culture was compared to that of planktonic cultures. Further, the performance of both the planktonic and immobilised Cu-adapted cultures (6.0 g/L of Cu2+) were compared with non-adapted planktonic and immobilised cells in the presence of increasing Cu2+ concentrations (0–50 g/L Cu2+).Both the Cu-adapted planktonic cells and the non-adapted immobilised cells demonstrated improved tolerance to Cu2+ stress relative to non-adapted planktonic cells. The Cu-adapted planktonic cells showed higher volumetric ferrous iron oxidation rates (0.0359 ± 0.0023 g Fe2+.L−1.h−1 at 22 g/L Cu2+) than the non-adapted immobilised cells (0.0331 ± 0.0021 g Fe2+.L−1.h−1) in the presence of Cu2+ concentrations exceeding 6 g/L. The Cu-adapted immobilised cells exhibited higher tolerance to Cu2+ stress and higher oxidation kinetics (0.0622 ± 0.0064 g Fe2+.L−1.h−1) than the Cu-adapted planktonic and non-adapted immobilised cells. This study provides a novel approach for improving culture performance and minimising the inhibitory effect of Cu2+ ion on L. ferriphilum dominated cultures. High microbial activity and metal tolerance of Cu-adapted immobilised cells presents an opportunity for immobilised microbial systems to be used both in bioleaching of e-waste streams, such as PCBs, and in bioleaching of mineral concentrates, ores and wastes with Cu2+-rich leachates.

Advances in E-Waste Recycling: Physical and Chemical Treatment Methods

The unprecedented rise in production and consumption of electronic devices has resulted in staggering amounts of electronic waste (e-waste). Improper recycling and disposal of e-waste can cause severe environmental and public health repercussions due to the presence of toxic substances like lead, mercury, and flame retardants. This article introduced advanced e-waste recycling technologies, focusing on physical and chemical treatment methods. Physical treatments such as gravity separation, electrostatic separation, and inverse flotation enable efficient and cost-effective recovery of precious metals like gold, silver, platinum, and rare earth metals from e-waste components. These physical processes are often environmentally friendly, scalable, and can handle diverse e-waste streams. Chemical treatments, including the dimethylformamide technique, supercritical fluid technique, and pyrolysis, allow for separating hazardous substances and recovering valuable materials not amenable to physical processes. Supercritical CO2 fluid destroys toxic organic compounds while enabling metal recovery. Pyrolysis converts plastics into liquid oil and gas products. By enhancing the separation and purification of valued materials, these physical and chemical e-waste recycling techniques provide more profitable, efficient, and sustainable solutions to ever-growing e-waste volumes.

Novel resource-efficient recovery of high purity indium products: Unlocking value from end-of-life mobile phone liquid crystal display screens

Liquid crystal display (LCD) screens found in most electrical and electronic equipment consume approximately 75% of the total indium produced globally. Due to indium’s unique properties and applications, the escalation in demand for the metal and the threat to supply of the metal, mined primarily as a by-product of zinc production, are critical. To mitigate these challenges the need to recover indium from end-of-life (EoL) products is becoming an imperative. In this work, EoL mobile phones (EoL-MPs), which represent a resource-rich stream for critical metals in general, and, specifically indium from LCDs, are used as a feedstock. Using a simulated Model Test System, with the task-specific ionic liquid, Cyphos 101, the optimal conditions for recovery of indium are determined before application to real samples. A complete hydrometallurgical process was developed for the recovery of indium from as-received EoL-MP LCDs as a four-step process involving pre-treatment, liquid-liquid extraction, elution and reduction, using the task-specific IL, Cyphos 101, as extractant. This novel hydrometallurgical process developed can achieve overall efficiencies of ≥ 90% for indium recovery in the form of two high-purity (≥ 99%) indium products of commercial value and offers a promising approach for recovery from any e-waste stream rich in indium. Moreover, this low energy process permits the reuse of the IL up to five consecutive times and has the potential to unlock value as polymeric films, glass substrate and liquid crystal for recycle and reuse within the circular economy.

Beneficiation and classification of ITO concentrate from waste LCD panel for industrial-scale indium extraction.

Currently, more than 55% of global indium production is consumed for indium tin oxide (ITO) production because of its excellent display properties mainly driven by demand for flat panel displays (FPDs) or LCDs. At the end of life, the waste LCD flows to the e-waste stream, accounts for 12.5% of the global e-waste, and is forecasted to be increasing progressively. These waste LCDs are potential wealth for indium that poses a threat to the environment. The volume of waste LCD generation is a global as well as national concern from a waste management perspective. Techno-economical recycling of this waste can be a panacea to the challenges associated with the lack of commercial technology and extensive research. Hence, a mass production capable of beneficiation and classification of ITO concentrate from waste LCD panels has been investigated. The mechanical beneficiation process for waste LCDs consists of five steps of operation, i.e., (i) size reduction by shredding by jaw milling, (ii) further size reduction to feed for ball milling, (iii) ball milling, (iv) classification to enrich ITO concentrate, and (v) characterization ITO concentrate and confirmation. The bench-scale process developed is intended to integrate with our indigenously developed dismantling plant (which can handle 5000 tons per annum) to handle separated waste LCD glass for indium recovery. Once scaled up, it can be integrated for continuous operation synchronized with the LCD dismantling plant.

A first comprehensive estimate of electronic waste in Canada

Detailed analysis of electronic waste (e-waste) generation and composition is of utmost importance for the proper management of growing e-waste stream worldwide, containing both hazardous and valuable materials. Considering the absence of such comprehensive and up-to-date studies in Canada, this work presents the first estimate of put-on-market electrical and electronic equipment (EEE), the in-use stocks of EEE and e-waste generation in Canada from 1971 to 2030 for 51 product categories comprising 198 product types. Using a dynamic material flow analysis (MFA), the put-on-market EEE is estimated based on trade data retrieved from national and international import and export statistics, and the in-use stocks of EEE and the resulting e-waste are calculated using the Weibull distribution function. The results show that the total mass of EEE within the 60-year period is estimated to be 42.3 million tonnes, with an annual average growth rate of approximately 0.5%. By 2030, the total accumulated in-use stock of EEE is estimated to exceed 13 million tonnes. The estimated e-waste over the 60-year timespan is 29.1 million tonnes. The total annual e-waste generation in Canada is calculated to be 252 kilo tonnes (kt) and 954 kt in the years 2000 and 2020 respectively, which is estimated to reach 1.2 million tonnes by 2030. The e-waste generation per capita increased from 8.3 kg in 2000 to 25.3 kg in 2020 and is estimated to reach 31.5 kg by 2030. This quantification provides valuable insights to policymakers for setting up targets for waste reduction and identifying the resource circularity potential for efficient management of e-waste.

Teaching Electrometallurgical Recycling of Metals from Waste Printed Circuit Boards via Slurry Electrolysis Using Benign Chemicals

The rapid growth of personal electronics has promoted a surge of e-waste worldwide. Among the e-waste stream, waste printed circuit boards (WPCBs) contain a lot of recyclable valuable metals that can incentivize the recycling operation when recovered. This pedagogical exercise demonstrates a simple electrocatalytic metal recovery strategy that works at room temperature and atmospheric pressure. Students can complete the exercise within 1.5–2 h and get to learn about electrocatalytic reactions and their parameters. The reaction can be powered by a couple of 1.5 V AA batteries and an electrolyte chemically similar to automobile antifreeze. Using quotidian objects can help students connect their laboratory learning with their daily lives. In addition to teaching electrochemistry concepts, we hope this exercise can raise awareness of the substantial increase of e-waste in recent years.

An Investigation on Bromine Content Assessment in e-Waste Plastics by Short Wave Infrared (SWIR) Spectroscopy

This paper reported a study based on the application of SWIR (shortwave infrared) spectroscopy to assess the presence of brominated flame retardants (BFRs) in plastic scraps coming from an e-waste stream composed by CRT (i.e., cathode-ray tube) monitors and televisions. An X-ray fluorescence (XRF) analysis was performed on plastic scraps to determine the presence and content of bromine (Br). The presence in plastic waste-flow streams, fed to or resulting from a recycling process, of individuals characterized by high concentrations of Br does not allow their use as secondary raw materials, imposing the need for an ad hoc separation processes. Chemometric methods were adopted for setting up models able to discriminate Br content. In more detail, principal component analysis (PCA) was used as an exploratory tool, while partial least squares (PLS) and locally weighted regression based on PLS regressions (LWRPLS) were used as multivariate regression models to test the ability of the spectra to predict Br content. The LWRPLS, showing an Rp2 of about 0.9, demonstrates the ability of this algorithm to establish a good correlation between the spectral signatures of plastic scraps and their Br content.

Metal bioleaching from printed circuit boards by bio-Fenton process: Optimization and prediction by response surface methodology and artificial intelligence models

Recycling printed circuit boards (PCBs) in the e-waste stream is essential for ecological protection and metal recycling for a circular economy. Efficient metal recovery from PCBs is highly dependent on the determination of the optimum combination of inputs in the recycling process. In this study, optimization and predictive modelling of the bio-Fenton process were performed employing the response surface methodology (RSM) and the artificial intelligence (AI) models for efficient enzymatic metal bioleaching from discarded cellphone PCBs. The Box-Behnken design (BBD) of RSM was chosen as the design matrix. Further, two AI models, i.e., support vector machine (SVM) and artificial neural network (ANN) were employed to predict complex metal bioleaching process. Experiments were performed based on variations of four input process parameters, namely, glucose oxidase (GOx) content (100–1000 U/L), Fe2+ content (10–50 mM), PCB pulp density (1–10 g/L), and shaking speed (150–450 rpm). Results revealed that the maximum simultaneous enzymatic metal extraction of 100% Cu, 70% Ni, 40% Pb, and 100% Zn was attained at the optimized conditions: GOx content: 300 U/L, Fe2+ content: 10 mM, pulp density: 1 g/L, and shaking speed: 335 rpm. A comparative analysis of the AI models suggested that the ANN-based model predicting more accurate results than the SVM-based model with coefficient of determination values > 0.99 for all the targeted metals. The FTIR analysis confirmed the partial disintegration of PCB polymeric base by OH radicals (OH•), which helped in liberating and exposing the embedded metals to the bio-Fenton solution. Further, the oxidation of metals by ferric ions produced from GOx-mediated oxidation of ferrous ions ensued efficient enzymatic metal bioleaching. Selective metal recovery of >99% was obtained by the chemical precipitation of bioleachate.

Characterization of industrially pre-treated waste printed circuit boards for the potential recovery of rare earth elements

Rare earth elements (REE) are classified as critical raw materials and the environmental impact of mining them is of growing concern. The recovery of REE from electronic waste (e-waste) could offer a more sustainable practice. Waste printed circuit boards (WPCBs) are an important resource in the e-waste stream due to their content of valuable materials. However, data regarding the concentration and distribution of REE in WPCBs is very limited. The aims of this research were: (a) to analyse the chemical composition of comminuted WPCBs prior to processing (industrially pre-treated) with emphasis on REE, and (b) to determine the distribution of REE and other metals in different size fractions of the pre-treated WPCBs. The samples were supplied by commercial e-waste recycling companies, which makes them representative of the e-waste processing industry in the UK. Correlation between elemental concentrations and particle size was analysed using Spearman’s rank correlation. Most REE concentrations were inversely correlated to the particle size. Concentrations of Y, La and Gd were found up to a thousand times higher in the smaller particle size compared with coarser particles. However, most of base metals including Cu, Sn, Pb and Zn did not show this trend. The present study highlights the occurrence of REE in comminuted WPCBs, and fine fractions as potential sources of these critical elements, currently not recovered during recycling process. A cost-effective sieving step is proposed to enrich the REE content for further recovery, prevent the possible loss of REE and maximize the total material recovered from WPCBs. • REE concentrations are inversely correlated to the particle size in comminuted WPCBs. • Concentrations of REE are up to a thousand times higher in finest fractions (<0.25 mm). • Fine fractions can contain over 60% of the total mass of some REE. • Simple and cost-effective sieving step can enhance yield of REE for recovery purposes. • Comminuted WPCBs are an untapped resource for REE recycling.

English

Reliable data on e-waste generation is important for environmentally sound management systems. This study models e-waste generation from existing data on electrical electronics imports, consumption and e-waste generation from Nigerian households. Structured questionnaires were used to obtain information on Electrical Electronic Equipment (EEE) use, reuse, and disposal from households in Nigeria households. Data from placed on the market (POM) were obtained from United Nations University (UNU) for five EEE types (TV, DVD player, refrigerator, desktop and laptop) in Nigeria between 1995 and 2019 using the apparent consumption method. A forecast up to 2020 and backcasts to 1980 were made based on these data. The lifetime profile for these five EEEs was modeled using the Weibull distribution function characterized by a time-varying shape parameter and a scale parameter. The POM data from 1980 to 2020 and the lifetime of the selected EEE from households were analyzed and fit into the Weibull lifetime distribution functions. The differences between reuse and non-reuse options show that around 54 million units of DVD players; 106 million units of CRT TV; 22 million units of the refrigerator; 11 million units of laptops and 24 million units of desktop computers would have been delayed from transiting into e-waste stream between 1981 and 2020 through reuse options. &nbsp; Key words: Electronic waste, electrical electronic equipment, lifetime distribution, re-use repair, recycling, Nigeria.

Quantification and characterization of recovered materials in the cycle of the informal household electronic waste dismantling in Buriram province, Thailand: A challenge towards sustainable management and circular economy.

The numerous amount of electronic waste (e-waste) has not been managed effectively resulting informal dismantling sites are being expanded in Thailand. The government attempts to improve the efficiency of an integrated e-waste management system, but baseline data of e-waste stream in informal sectors are insufficient. This research aimed to investigate the inflow and outflow of the materials throughout the informal e-waste dismantling processes at the well-known second-largest community in Buriram province during 2017-2018. To describe the quantities of dismantled materials, a material flow analysis was performed. The overall amount of e-waste taken to the community was estimated to be in the range of 1593-12,943 tonnes year-1. Valuable materials could be recovered at more than 90% (by mass) from fans, refrigerators, washing machines, microwaves and air conditioners. The amount of e-waste residue that the local administrative organization had to handle was up to 1144 tonnes year-1. The quantitative data retrieved from this study could provide a satisfactory equation for estimating the amount of separated valuable and non-valuable materials. Recyclable materials from dismantling have an economic incentive, e-waste dismantlers in a small and large household group that can earn approximately 798 and 1262 USD month-1 income, respectively. The notable e-waste characterization and quantification of recovered materials would be useful for improving the potential circular flow of e-waste in Thailand.

Design for Reuse: residual value monitoring of power electronics’ components

Extending electronics’ lifespan is a major issue in Design for Sustainability. Power electronic components are a continuously growing part of our daily good service usages from the laptop charger (10-100 W), the home air conditioning (1-10 kW), the solar power plant (1-100 kW), to the railway electric mobility (1-100 MW). They drastically contribute to increasing the e-waste stream since device volume is proportional to power ratings. Repairing conversion systems challenges designers in the way the systems should be designed to be maintained over the years. In addition, introducing circular economy with electronic component (or subsystems) reuse supposes evaluating their residual value in case of power electronics. This paper firstly introduces from the state of the art the residual value evaluations to define the relevant parameters that should be included in the case of power electronic components, and a method to estimate this value is proposed.

It All Hinges on China: Environmental Governance in the Twenty-First Century

It All Hinges on China: Environmental Governance in the Twenty-First Century

A Review on Chemical versus Microbial Leaching of Electronic Wastes with Emphasis on Base Metals Dissolution

There is a growing interest in electronic wastes (e-wastes) recycling for metal recovery because the fast depletion of worldwide reserves for primary resources is gradually becoming a matter of concern. E-wastes contain metals with a concentration higher than that present in the primary ores, which renders them as an apt resource for metal recovery. Owing to such aspects, research is progressing well to address several issues related to e-waste recycling for metal recovery through both chemical and biological routes. Base metals, for example, Cu, Ni, Zn, Al, etc., can be easily leached out through the typical chemical (with higher kinetics) and microbial (with eco-friendly benefits) routes under ambient temperature conditions in contrast to other metals. This feature makes them the most suitable candidates to be targeted primarily for metal leaching from these waste streams. Hence, the current piece of review aims at providing updated information pertinent to e-waste recycling through chemical and microbial treatment methods. Individual process routes are compared and reviewed with focus on non-ferrous metal leaching (with particular emphasis on base metals dissolution) from some selected e-waste streams. Future outlooks are discussed on the suitability of these two important extractive metallurgical routes for e-waste recycling at a scale-up level along with concluding remarks.

Appraisal of Households’ Knowledge and Perception towards E-Waste Management in Limpopo Province, South Africa

The generation of electronic waste (e-waste) is increasing at an alarming rate in South Africa. This waste stream is also emanating from household appliances due to beneficial attributes accrued to the use of these electronic devices. At the same time, these devices are a source of concern considering the environmental impacts as well the threat of health hazards they possess to human wellbeing. In appraising household knowledge and perception on e-waste management in Limpopo Province of South Africa, 200 semi-structured, self-administered questionnaires were used in eliciting data from the participants. The results indicated that 76% of the respondents believed that e-waste streams have negatively affected their environment. Additionally, 85% of the survey households are willing to pay for the proper disposal of their e-waste. Furthermore, the results indicated a statistically significance between gender and knowledge on e-waste management (p-value 0.003) while there was no statistically significant difference between gender and perception (p-value 0.318) on e-waste management. Based on the results, the study recommends awareness and educational campaigns as a step in changing the perception of households on e-waste and environmental consciousness.