Review E-Wastes: Bridging the Knowledge Gaps in Global Production Budgets, Composition, Recycling and Sustainability Implications Hem Ghimire and Parisa A. Ariya * Department of Atmospheric and Oceanic Sciences, McGill University, 801 Sherbrooke Street West, Montreal, QC H3A 2K6, Canada; [email protected] * Correspondence: [email protected] Received: 31 July 2020; Accepted: 31 August 2020; Published: 9 September 2020 Abstract: Rapid urbanization, advancements in science and technology, and the increase in tech-savviness of consumers have led to an exponential production of a variety of electronic equipment. The global annual growth rate of e-waste volume exceeds the growth rate of the human population. Electronic waste has now become a point of concern globally (53.6 million metric tons, 2019). However, merely 17.4% of all global e-waste is properly collected and recycled. China is the largest contributor to the global production of e-waste (~19%), the second being the United States. Indeed, only 14 countries generated over 65% of global e-waste production in 2019. E-wastes contain a wide range of organic, and inorganic compounds including various metals. Emerging contaminants like plastics are amongst the fastest growing constituents of electronic waste. The current challenges include the lack of reliable data, inadequate identification and quantification of new emerging materials, limited effectiveness of current recycling technologies, need for cutting-edge detection and recycling technologies, and the lack of e-waste management policies and international collaboration. In this review, we strive to integrate the existing data on production rates at different spatial scales, composition, as well as health, economical, and environmental challenges, existing recycling technologies; explore tangible solutions; and encourage further sustainable technology and regulatory policies. Keywords: electronic equipment; e-waste; WEEE; e-waste handling; recycling; zero net energy; nanoparticles; sustainability 1. Introduction Electrical and electronic equipment (EEE) has become a backbone of modern human society. They are considered as a symbol of a modern lifestyle, comfort, efficiency, and even prosperity in developing countries. However, every EEEs become electronic waste at the end. As per the European Union (EU) WEEE Directive, e-waste is defined as “the waste from electrical and electronic equipment (WEEE) that includes all the components of electronic equipment, its subassemblies, and consumables which are the part of the product at the time it is discarded” [1]. E-waste thus includes outdated, damaged, or unwanted electronic materials. E-waste is a fast-growing sector in the modern global economy. This acceleration is dependent on several factors such as rapid economic growth, urbanization, industrialization, and increased demand for consumer goods [2,3]. The Global E-waste Monitor 2020 reports the world generated 53.6 Mt of e-waste in 2019, up by 9.2 Mt since 2014 and is anticipated to surpass a staggering 74.7 Mt by 2030 [3]. In developing countries, the number of middle-class families with higher purchasing capacity is rapidly increasing. Therefore, people are spending more than ever before on electronic instruments. Many substances in e-waste are toxic (e.g., heavy metals such as lead, mercury, chromium, cadmium), Sustain. Chem. 2020, 1, 154–182; doi:10.3390/suschem1020012 www.mdpi.com/journal/suschem Sus. Chem. 2020, 1, FOR PEER REVIEW 2 Sustain. Chem. 2020, 1 155 Many substances in e-waste are toxic (e.g., heavy metals such as lead, mercury, chromium, cadmium), polychlorinatedpolychlorinated biphenyls (PCBs), brominated flameflame retardantsretardants (BFRs),(BFRs), etc.etc. Open burning of circuit boardsboards/wires/wires or or materials materials containing containing both both chlori chlorinene and and bromine bromine can canproduc producee toxic toxic byproducts byproducts such suchas multiple as multiple chlorinated chlorinated and brominated and brominated dioxin compounds dioxin compounds including includingmixed halogenated mixed halogenated dibenzo-p- dibenzo-dioxins/dibenzofuransp-dioxins/dibenzofurans [4–6]. [4–6]. Developed countries such as Japan and in thethe EuropeanEuropean Union,Union, and NorthNorth AmericaAmerica have thethe potentialpotential andand infrastructureinfrastructure to to recycle recycle e-waste e-waste [7 [7];]; however, however, a significanta significant amount amount of of e-waste e-waste is legallyis legally or illegallyor illegally transported transported to low-income to low-income countries countries having having lax or nolax regulation or no regulation for e-waste for [ 8e-waste]. This shipment[8]. This ofshipment the waste of isthe motivated waste is bymotivated strict e-waste by strict policies e-wa andste policies higher cost and to higher recycle cost hazardous to recycle substances hazardous in developedsubstances countriesin developed than countries the cost tothan ship the them cost to to developing ship them nations.to developing The Global nations. E-waste The Global monitor E- 2020waste reports monitor that 2020 formally reports collected that formally/recycled collected/re e-wastecycled increased e-waste by 1.8 increased Mt since by 2014 1.8 Mt to reach since ~17.4%2014 to inreach 2019. ~17.4% The whereabouts in 2019. The of thewhereabouts remaining of waste the isremaining largely unaccounted waste is largely for—apparently, unaccounted this for— was illegallyapparently, traded, this incinerated,was illegally or traded, dumped incinerated, in landfills or [3]. dumped Figure1 showsin landfills a schematic [3]. Figure representation 1 shows a ofschematic generated, representation recycled, and of undocumentedgenerated, recycled, e-waste and recordedundocumented worldwide e-waste in2019. recorded Some worldwide developing in countries2019. Some such developing as India have countries recently such started as India to impose have e-wasterecently rules,started with to tepidimpose results. e-waste Although rules, with 71% oftepid the globalresults. population Although is 71% covered of bythe the global e-waste popu policieslation and is legislation,covered by their theproper e-waste implementation policies and islegislation, yet to be achievedtheir proper [3] rendering implementation informal is sectors,yet to be mostly achieved in developing [3] rendering countries, informal to handlesectors, e-waste mostly within developing little or no countries, safety precautions to handle and e-waste knowledge with andlittle putting or no safety both the precautions environment and and knowledge public health and atputting serious both risk the [9– environment11]. and public health at serious risk [9–11]. Figure 1. SimplifiedSimplified schematic of e-waste sources and sinkssinks (2019 data), the waste deposit picture was obtained fromfrom thethe publicpublic domain.domain. E-waste isis a burninga burning topic topic of interest of interest in sustainability in sustainability as it touches as it ontouches economy, on energy,economy, technology, energy, culturetechnology, and communication,culture and communication, waste management, waste management, human health, human ecosystem health, health, ecosystem international health, ainternationalffairs, and policy. affairs, This and multidisciplinary policy. This multidiscipl challengeinary iscomplex. challenge However,is complex. there However, is an opportunity there is an foropportunity sustainable for growth. sustainable The growth. value of The raw value materials of raw in e-wastematerials generated in e-waste in generated 2019 is estimated in 2019 tois beestimated worth nearlyto be worth $57 billion nearly [ 3$57]. Therebillion is [3]. thus There a great is thus potential a great to potential change to e-waste change from e-waste a problem from a toproblem a unique to a opportunity unique opportunity illustrated illustrated by the low by the documented low documented collection collection and recycling and recycling of the waste.of the However,waste. However, the opportunity the opportunity jointly comesjointly withcomes challenges with challenges such as such the heterogeneity as the heterogeneity of e-waste, of e-waste, cost of handlingcost of handling and treatment, and treatment, toxic emissions, toxic emissions, disposal disposal of unwanted of unwanted and hazardous and hazardous remains, remains, and lack and of internationallack of international collaboration. collaboration. InIn this this review, review, we westrive strive to integrate to integrate the current the knowledge, current knowledge, analyze the analyze challenges the (economical, challenges (economical,environmental, environmental, health, technological, health, technological, governmental, governmental, policy and implementation, policy and implementation, etc.), and explore etc.), andsustainable explore sustainablesolutions for solutions better for e-waste better e-wastemanagement. management. We also We also propose propose selected selected succinct recommendations forfor a a more more sustainable sustainable future future for e-waste,for e-waste, which which would woul required require a progressive a progressive policy andpolicy circular and circular economy. economy. Sustain. Chem. 2020, 1 156 2. Composition of E-Waste E-waste comprises of a diverse range of substances depending upon age of e-waste, type, and categories of EEEs [12,13]. A mobile phone can contain more than 40 reusable elements [14–16]. Some materials found in e-waste are precious metals