Distinct Urban Mines: Exploiting secondary resources in unique anthropogenic spaces

Waste of electrical and electronic equipment management from the perspective of a circular economy: A Review

In addition to the difficulties involved in the management of conventional solid waste, the management of waste of electrical and electronic equipment (WEEE) is significantly more complex due to its unusual chemical composition and fast generation. Both developed and developing countries have been looking for solutions to deal with the problems caused by the growing flow of WEEE, especially regarding sustainable solutions based on reducing resource exploitation by the recovery of materials from this type of waste. In this context, this work presents a quali-quantitative and comprehensive literature review of the publications on the management of WEEE, from the perspective of a circular economy. The results showed that the first publications on the topic appear in 2006, with a significant increase from 2015, the year when the Circular Economy Action Plan was instituted in the European Community. The most prominent authors have been giving emphasis to researches on recycling, reuse and technologies for the recovery of materials/energy from WEEE. Nevertheless, few studies have been found focusing on the prevention/reduction in WEEE generation, priority actions of the WEEE management hierarchy. The works analysed show that the current management of WEEE, despite considering the circularity of materials, prioritizes the development of technological solutions of the end-of-pipe type, greatly represented by the recovery of materials, instead of preventing the generation, which may be detrimental to long-term sustainability. The work ends with the presentation of a SWOT-TOWS (strengths, weaknesses, opportunities and threats) analysis conducted to define the main strategies for the improvement of WEEE management from a circular economy perspective.

Fungal biotechnology for urban mining of metals from waste printed circuit boards: A review

Rapid surge in electronic waste (e-waste) and its unscientific handling has an adverse impact on humans and the environment. Waste printed circuit board (WPCB), an integrated component of e-waste, has a high metallic content that includes both toxic and precious metals. Therefore, metal recovery is essential not just to avoid environmental degradation but also for economic growth. The current literature analysis focuses on one such eco-friendly approach, known as fungal biotechnology, for extracting metals from WPCBs. Among diverse bioleaching agents, fungi have shown promising metal extraction efficiency (Al: 65-96%; Co: 45-90%; Cu: 34-100%; Ni: 8-95%; Mn: 70-95%; Pb: 27-95%; Zn: 54-99%) and the ability to work in a wide pH range. However, in terms of metal recovery from WPCBs, fungal bioleaching has been less explored. This review, thus, assesses the fungal biotechnology for metal extraction from WPCBs and discusses the associated mechanism and kinetics involved. Different process parameters affecting the fungal bioleaching have also been discussed briefly. The review highlights that, while this process has enough potential, some associated drawbacks hinder its practical applicability on an industrial scale. Lastly, some suggestions for scaling up and reducing the cost of the process have been made, which need to be addressed.

Characteristics of unorganized emissions of microplastics from road fugitive dust in urban mining bases

Nowadays, plastic pollution attracts attention, while data on microplastic (MP) emissions to atmosphere from urban mining bases are rarely quantified. In this paper, the emission characteristics of MPs in road fugitive dust from two urban mining bases were studied, the emission factors of MPs from road fugitive dust source were updated, and emission inventories were established. It is estimated that the waste glass recycling base and the e-waste dismantling plant emit 1265.53 g and 40.5 g of MPs into atmosphere respectively each year, with the highest percentage of tire micro-rubber. The roads with the most emissions are located in the middle of warehouses and workshops. Emission factors for MPs mainly depend on average vehicle weight, and heavy vehicles cause more MP emissions. Uncertainty analysis of the inventory indicated that the random error of MP emissions on a single road in waste glass recycling base was -79.1%-187.1%, while in e-waste dismantling plant was -62.7%-102.05%, which is mainly related to the silt loading. This study completes the quantitative data on the unorganized emissions of MPs from road fugitive dust in these two typical urban mining bases, and provides guidance for air pollution prevention and control.

A review on recent advancements in recovery of valuable and toxic metals from e-waste using bioleaching approach

This review is intent on the environmental pollution generated from printed circuit boards and the methods employed to retrieve valuable and hazardous metals present in the e-wastes. Printed circuit boards are the key components in the electronic devices and considered as huge e-pollutants in polluting our surroundings and the environment as a whole. Composing of toxic heavy metals, it causes serious health effects to the plants, animals and humans in the environment. A number of chemical, biological and physical approaches were carried out to recover the precious metals and to remove the hazardous metals from the environment. Chemical leaching is one of the conventional PCBs recycling methods which was carried out by using different organic solvents and chemicals. Need of high cost for execution, generation of secondary wastes in the conventional methods, forces to discover the advanced recycling methods such as hydrometallurgical, bio-metallurgical and bioleaching processes to retrieve the valuable metals generate through e-wastes. Among them, bioleaching process gain extra priority due to its higher efficiency of metal recovery from printed circuit boards. There are different classes of microorganisms have been utilized for precious metal recovery from the PCBs through bioleaching process such as chemolithoautotrophy, heterotrophy and different fungal species including Aspergillus sp. and Penicillium sp. The current status and scope for further studies in printed circuit boards recycling are discussed in this review.

Bioleaching of copper and nickel from mobile phone printed circuit board using Aspergillus fumigatus A2DS

The recovery of metals from electronic waste was investigated by using fungal strain Aspergillus fumigatus A2DS, isolated from the mining industry wastewater. Fifty-seven percent of copper and 32% of nickel were leached (analyzed by Inductively Coupled Plasma Atomic Emission Spectroscopy (ICP-OES)) by the organism after one-step leaching at a temperature of 30 °C (shaking condition for 7 days). Maximum % of copper and nickel were obtained at a pH of 6 (58.7% Cu and 32% Ni), the temperature of 40 °C (61.8% Cu and 27.07% Ni), a pulp density of 0.5% (62% Cu and 42.37% Ni), and inoculums of 1% (58% Cu and 32.29% Ni). The XRD pattern of PCB showed 77.6% of copper containing compounds. XRD analysis of the leachate residue showed only 23.2% Euchorite (ASCu2H7O8) and 9.4% other copper containing compounds, indicating the leaching property of the fungus. HPLC analysis of the spent medium showed the presence of different acids like citric, succinic, and fumaric acid. The FTIR spectrum showed a decrease in carboxylic stretching in the leachate produced after bioleaching using spent medium. ICPOES of the leachate obtained using spent medium showed that 61% of the copper and 35% of nickel were leached out after seven days of incubation at shaking condition and 57% of copper and 32.8% of nickel at static condition confirming acidolysis property of the strain. A. fumigatus A2DS metal absorption and adsorption ability were observed using transmission electron microscopy (TEM) and scanning electron microscopy energy dispersive X-ray (SEM-EDX) respectively. The results thus indicate that bioleaching of Cu and Ni is bioleached by A. fumigatus A2DS.

Global E-waste management: Can WEEE make a difference? A review of e-waste trends, legislation, contemporary issues and future challenges

Waste electrical and electronic equipment (WEEE) comprises a globally important waste stream due to the scarcity and value of the materials that it contains; annual generation of WEEE is increasing by 3-5% per annum. The effective management of WEEE will contribute critically to progress towards (1) realisation of the United Nations' Sustainable Development Goals, (2) a circular economy, and (3) resource efficiency. This comprehensive review paper provides a critical and contemporary examination of the current global situation of WEEE management and discusses opportunities for enhancement. Trends in WEEE generation, WEEE-related policies and legislation are exemplified in detail. Four typical future WEEE management scenarios are identified, classified and outlined. The European Community is at the forefront of WEEE management, largely due to the WEEE Directive (Directive 2012/19/EU) which sets high collection and recycling targets for Member States. WEEE generation rates are increasing in Africa though collection and recycling rates are low. WEEE-related legislation coverage is increasing in Asia (notably China and India) and in Latin America. This review highlights emerging concerns, including: stockpiling of WEEE devices; reuse standards; device obsolescence; the Internet of Things, the potential for collecting space e-debris, and emerging trends in electrical and electronic consumer goods. Key areas of concern in regard to WEEE management are identified: the partial provision of formal systems for WEEE collection and treatment at global scale; further escalation of global WEEE generation (increased ownership, and acceleration of obsolescence and redundancy); and absence of regulation and its enforcement. Measures to improve WEEE management at global scale are recommended: incorporation of circular economy principles in EEE design and production, and WEEE management, including urban mining; extension of WEEE legislation and regulation, and improved enforcement thereof; harmonisation of key terms and definitions to permit consistency and meaning in WEEE management; and improvements to regulation and recognition of the informal WEEE management sector.

A Systematic Literature Network Analysis of Existing Themes and Emerging Research Trends in Circular Economy

The debate about Circular Economy (CE) has been increasingly enriched by academics through a vast array of contributions, based on several theoretical perspectives and emanating from several research domains. However, current research still falls short of providing a holistic and broader view of CE, one that combines existing themes and emerging research trends. Accordingly, based on a Systematic Literature Network Analysis, this paper tackles this gap. First, a Citation Network Analysis is used to unearth the development of the CE literature based on papers’ references, whilst the Main Path is traced to detect the seminal papers in the field through time. Second, to consider the literature in its broader extent, a Keywords Co-Occurrence Network Analysis is conducted based on papers’ keywords, whereby all papers in the dataset, including the non-cited papers, are assessed. Additionally, a Global Citation Score analysis is conducted to uncover the recent breakthrough research, in addition to the Burst Analysis used to detect the dynamic development of CE literature over time. By doing so, the paper explores the development of the CE body of knowledge, reveals its dynamic evolution over time, detects its main theoretical perspectives and research domains, and highlights its emerging topics. Our findings unfold the evidence of eight main trends of research about CE, unearth the path through which the CE concept emerged and has been growing, and concludes with promising avenues for future research.

Entrepreneurial Drivers for the Development of the Circular Business Model: The Role of Academic Spin-Off

Circular Economy represents today a new economic paradigm based on the environment and on the recovery of material. The pursuit of this change can be implemented through different policies with a top-down or bottom-up approach. Following the latter approach Spin-Offs, typically defined as “Science Based” companies, represent an alternative tool to promote technology transfer. In other words, they represent a bridge between the research and the production system. This part of the study is part of a larger and more complex project whose objective is to verify whether the development of research Spin-Offs and in particular academics, operating in the environment sector, or more generally sustainable, facilitate the transition from the classic model of linear economics to the innovative model of circular economics. The aim of the paper is to investigate how spin off enterprises can be a driver for the development of a Circular Business Model and to facilitate the transition from the classical model of linear economy to the new model of Circular Economy. At the methodological level, a multiple compared analysis was made between a sample of firms located in Lazio Region- Italy, that operates in the area of green economy Smart Specialization Strategy (S3). The analysis shows a rapid succession of variables that lead to the identification of four scenarios, deriving from the interconnection of the outcome: “closed loop”, “open loop” and the presence or absence of Circular Economy practices. The result confirms that the Academic Spin-Offs can be a driver of Circular economy, as long as that fall within the IV scenario, characterized by the interconnection of an open loop system that works in a circular approach. The “High valorization of waste” represents the discriminant in this scenario, which allows to activate a cascade system in a multi-stakeholder perspective.

Bioleaching assisted foam fractionation for recovery of gold from the printed circuit boards of discarded cellphone

Present work was focused on recovering gold (Au) from the printed circuit boards (PCBs) of discarded cellphone by bioleaching assisted continuous foam fractionation. First, the cyanide-producing strains of Pseudomonas putida and Bacillus megaterium were co-cultured in order to supply a high cyanide concentration in the nutrient solution for mobilizing Au from waste PCBs (WPCBs). Bioleaching conditions were optimized by using response surface methodology. Under the suitable bioleaching conditions of pH of 10.0, pulp density of 5 g/L and leaching time of 34 h, the Au mobilization percentage was 83.59%. The leaching liquor with an Au concentration of 1.34 mg/L could be used as the feeding solution of continuous foam fractionation after removing solid particles and cell biomass. In order to strengthen foam drainage, a novel internal component of foam fractionation column was developed. Under the suitable operation conditions of CTAB concentration of 0.2 g/L, volumetric air flow rate of 100 mL/min and feed flow rate of 10 mL/min, the enrichment ratio and recovery percentage of Au were 43.62 and 87.46%, respectively. This study is expected to provide an effective strategy to recover Au from WPCBs, and to supplement the depleting natural resources.

Investigating the reasons for storage of WEEE by residents - A potential for removal from households

Some categories of waste electrical and electronic equipment (WEEE) escape legal methods of disposal. The waste stream intended for recycling is sometimes disrupted because of the stockpiling of end of life (EOL) equipment in households. In some cases this equipment may be non-functional or broken but it is kept by the individuals. It is usually equipment of small dimensions that is involved in these instances. The main purpose of this study is to identify the reasons that individuals stockpile EOL equipment. A behavioural model of WEEE disposal by household individuals is proposed and tested with a survey. Results from questionnaires show the differences in behaviour for individual categories of WEEE included in the survey conducted in Poland. The results show the significance of education, age, gender and type of residence on behavioural patterns relating to disposal of waste equipment. The most likely to be stockpiled are computer accessories and other information technology equipment, comprising above 60% of responses, and mobile phones, being above 80% of responses. The most frequent reason for stockpiling is intended possible use of the equipment in the future. The results of this research can be used in campaigns aimed at increasing household awareness against stockpiling.

Biotechnological strategies for the recovery of valuable and critical raw materials from waste electrical and electronic equipment (WEEE) - A review

Critical raw materials (CRMs) are essential in the development of novel high-tech applications. They are essential in sustainable materials and green technologies, including renewable energy, emissionfree electric vehicles and energy-efficient lighting. However, the sustainable supply of CRMs is a major concern. Recycling end-of-life devices is an integral element of the CRMs supply policy of many countries. Waste electrical and electronic equipment (WEEE) is an important secondary source of CRMs. Currently, pyrometallurgical processes are used to recycle metals from WEEE. These processes are deemed imperfect, energy-intensive and non-selective towards CRMs. Biotechnologies are a promising alternative to the current industrial best available technologies (BAT). In this review, we present the current frontiers in CRMs recovery from WEEE using biotechnology, the biochemical fundamentals of these bio-based technologies and discuss recent research and development (R&D) activities. These technologies encompass biologically induced leaching (bioleaching) from various matrices,biomass-induced sorption (biosorption), and bioelectrochemical systems (BES).

Application of indirect non-contact bioleaching for extracting metals from waste lithium-ion batteries

Applying biohydrometallurgy for metal extraction and recovery from mixed and polymetallic wastes such as electronic waste is limited due to microbial inhibition at low pulp densities and substrate (iron and sulfur) limitation. Here, we investigated the application of indirect non-contact bioleaching with biogenic ferric iron and sulfuric acid to extract metals from lithium-ion battery (LIB) waste. Results showed that although a single leach stage at ambient temperature only facilitated low leach yields (<10%), leach yields for all metals improved with multiple sequential leach stages (4 × 1 h). Biogenic ferric leaching augmented with 100 mM H₂SO₄ further enabled the highest leach yields (53.2% cobalt, 60.0% lithium, 48.7% nickel, 81.8% manganese, 74.4% copper). The proposed use of bioreagents is a viable and a more environmentally benign alternative to traditional mineral processing, which could be further improved by appropriate pre-treatment of the LIB waste.

Urban mining demonstration bases in China: A new approach to the reclamation of resources

This paper aims to examine a key Chinese circular economy program, the Urban Mining Demonstration Base Construction (UMDBC) Program, for its successes, experiences and existing problems. Using publicly available data and detailed investigation and analysis, we discuss the details of the UMDBC Program. Although the whole program has been implemented and has made significant progress, some problems exist. Our findings suggest that it is more important for the Chinese government to provide an effective legal framework than merely provide financial support. The experiences and lessons from research into the UMDBC Program could serve as an example to other developing countries facing environmental and resource pressures.

Multistage leaching of metals from spent lithium ion battery waste using electrochemically generated acidic lixiviant

Lithium ion battery (LIB) waste contains significant valuable resources that could be recovered and reused to manufacture new products. This study aimed to develop an alternative process for extracting metals from LIB waste using acidic solutions generated by electrolysis for leaching. Results showed that solutions generated by electrolysis of 0.5 M NaCl at 8 V with graphite or mixed metal oxide (MMO) electrodes were weakly acidic and leach yields obtained under single stage (batch) leaching were poor (<10%). This was due to the highly acid-consuming nature of the battery waste. Multistage leaching with the graphite electrolyte solution improved leach yields overall, but the electrodes corroded over time. Though yields obtained with both electrolyte leach solutions were low when compared to the 4 M HCl control, there still remains potential to optimise the conditions for the generation of the acidic anolyte solution and the solubilisation of valuable metals from the LIB waste. A preliminary value proposition indicated that the process has the potential to be economically feasible if leach yields can be improved, especially based on the value of recoverable cobalt and lithium.

An Extended Model for Tracking Accumulation Pathways of Materials Using Input–Output Tables: Application to Copper Flows in Japan

Recycling has become increasingly important as a means to mitigate not only waste issues but also problems related to primary resource use, such as a decrease in resource availability. In order to promote and plan future recycling efficiently, detailed information on the material stock in society is important. For a detailed analysis of material stocks, quantitative information on flows of a material, such as its accumulation pathways, final destinations, and its processing forms, are required. This paper develops a model for tracking accumulation pathways of materials using input–output tables (IOTs). The main characteristics of the proposed model are as follows: (1) accumulations in sectors other than the final demand sectors (i.e., endogenous sectors) are explicitly evaluated, (2) accumulations as accompaniments to products, such as containers and packaging, are distinguished from the products, and (3) processing forms of materials are considered. The developed model is applied to analyze copper flows in Japan using the Japanese IOTs for the year 2011. The results show that accumulations of copper in endogenous sectors were not negligibly small (9.24% of the overall flow). Although accumulations of copper as accompaniments were very small, they may be larger for other materials that are largely used as containers or packaging. It was found that the destinations of copper showed different characteristics depending on the processing forms.

Modelling the correlations of e-waste quantity with economic increase

Waste from Electrical and Electronic Equipment (WEEE or e-waste) is regarded as one of the fastest growing waste streams in the world and is becoming an emerging issue owing to adverse consequences on the natural environment and the human health. This research article reveals the presence of a strong linear correlation among global e-waste generation and Gross Domestic Product. The obtained results indicate that the best fit for data can be reached by comparing e-waste collected volumes and GDP PPS. More in detail, an increase of 1000 GDP PPS means an additional 0.27kg of e-waste collected and 0.22kg of e-waste reused/recycled. Furthermore, for each additional citizen, there will be an increase of 7.7kg of e-waste collected and 6.2kg of e-waste reused/recycled. The better collection of e-waste acts an important role concerning the circular economy, and it can be an advantageous approach. Therefore, e-waste could be considered as an opportunity for recycling or recovery of valuable metals (e.g., copper, gold, silver, and palladium), given their significant content in precious metals than in mineral ores.

Using choice architecture to exploit a university Distinct Urban Mine

There are widespread concerns regarding the potential future scarcity of ferrous and non-ferrous materials. However, there are already potentially rich reserves of secondary materials via high ownership of Electrical and Electronic Equipment (EEE) in economically-developed nations. Young people are particularly high consumers of EEE, thus university students and campuses may present an opportunity to harness this potential. University Distinct Urban Mines (DUM) may be used to exemplify how potential reserves of secondary metals may be exploited, and could contribute to the transition from a linear to a circular economy. This study aimed to evaluate small household appliances (SHA) DUM from a UK university, with the objectives to identify and quantify student households' SHA ownership, WEEE recycling, stockpiling and discarding habits amongst student households, assess and evaluate the monetary potential of SHA DUM at UK level, and propose methods to exploit DUM for universities in the UK. To this purpose, a quantitative survey was undertaken to measure students' ownership and discarding behaviour with respect to SHA. The amounts of ferrous and non-ferrous materials were then estimated and converted to monetary values from secondary materials market data to appraise the SHA DUM overall value. Thirty-five per cent of SHA are discarded in the general refuse. Broken personal care appliances (PCA) tend to be discarded due to hygiene and small size factors. When in working order, SHA tend to be equally reused, recycled or stockpiled. We conclude that a total of 189 tonnes of ferrous and non-ferrous materials were available via discarding or being stockpiled at the University of Southampton. Extrapolated to UK higher education level, discarded and stockpiled SHA represent a potential worth ∼USD 11 million. To initiate DUM exploitation within Higher Education campuses, we suggest improving users' choice architecture by providing collection methods specific to broken SHA.

An investigation of trends in precious metal and copper content of RAM modules in WEEE: Implications for long term recycling potential

Precious metal (PM) and copper content of dynamic-RAM modules placed on the market during 1991-2008 has been analysed by AAS following comminution and acid digestion. Linear regression analysis of compositional data ordered according to sample chronology was used to identify historic temporal trends in module composition resulting from changes in manufacturing practices, and to project future trends for use in more accurate assessment of future recycling potential. DRAM was found to be 'high grade' waste with: stable levels of gold and silver over time; 80% reduction in palladium content during 1991-2008; and 0.23g/module/year increase in copper content with a 75% projected increase from 2008 by 2020. The accuracy of future recycling potential projections for WEEE using current methods based on static compositional data from current devices is questionable due to likely changes in future device composition. The impact on recycling potential projections of waste laptops, smart phones, cell phones and tablets arising in Europe in 2020 resulting from a 75% increase in copper content is considered against existing projections using static compositional data. The results highlight that failing to consider temporal variations in PM content may result in significant discrepancies between projections and future recycling potential.

Global demand for rare earth resources and strategies for green mining

Rare earth elements (REEs) are essential raw materials for emerging renewable energy resources and 'smart' electronic devices. Global REE demand is slated to grow at an annual rate of 5% by 2020. This high growth rate will require a steady supply base of REEs in the long run. At present, China is responsible for 85% of global rare earth oxide (REO) production. To overcome this monopolistic supply situation, new strategies and investments are necessary to satisfy domestic supply demands. Concurrently, environmental, economic, and social problems arising from REE mining must be addressed. There is an urgent need to develop efficient REE recycling techniques from end-of-life products, technologies to minimize the amount of REEs required per unit device, and methods to recover them from fly ash or fossil fuel-burning wastes.