Environmentally sound system for E-waste: Biotechnological perspectives

A raising alarm on the current global electronic waste situation through bibliometric analysis, life cycle, and techno-economic assessment: a review

Electronic waste (E-waste) production worldwide is increasing three times faster than the growth of the global population, and it is predicted that the total volume of E-waste will reach 74 million tonnes by 2030. United Nations warned that unless emissions of heat-trapping gases are drastically reduced, humanity will face catastrophic climate change. We created a bibliometric analysis and discussed the life cycle and techno-economic assessments of the current E-waste situation. We found trending E-waste topics, particularly those related to industrial facilities implementing a circular economy framework and improving the recycling methods of lithium-ion batteries, and this was linked to the topic of electric vehicles. Other research themes included bioleaching, hydrometallurgy, reverse logistics, heavy metal life cycle assessment, and sustainability. These topics can interest industrial factories and scientists interested in these fields. Also, throughout techno-economic assessments, we highlighted several economic and investment opportunities to benefit stakeholders from E-waste recycling. While the rate of E-waste is increasing, consumer education on the proper E-waste management strategies, a collaboration between international organizations with the industrial sector, and legislation of robust E-waste regulations may reduce the harmful effect on humans and the environment and increase the income to flourish national economies.

Driving sustainable circular economy in electronics: A comprehensive review on environmental life cycle assessment of e-waste recycling

E-waste, encompassing discarded materials from outdated electronic equipment, often ends up intermixed with municipal solid waste, leading to improper disposal through burial and incineration. This improper handling releases hazardous substances into water, soil, and air, posing significant risks to ecosystems and human health, ultimately entering the food chain and water supply. Formal e-waste recycling, guided by circular economy models and zero-discharge principles, offers potential solutions to this critical challenge. However, implementing a circular economy for e-waste management due to chemical and energy consumption may cause environmental impacts. Consequently, advanced sustainability assessment tools, such as Life Cycle Assessment (LCA), have been applied to investigate e-waste management strategies. While LCA is a standardized methodology, researchers have employed various routes for environmental assessment of different e-waste management methods. However, to the authors' knowledge, there lacks a comprehensive study focusing on LCA studies to discern the opportunities and limitations of this method in formal e-waste management strategies. Hence, this review aims to survey the existing literature on the LCA of e-waste management under a circular economy, shedding light on the current state of research, identifying research gaps, and proposing future research directions. It first explains various methods of managing e-waste in the circular economy. This review then evaluates and scrutinizes the LCA approach in implementing the circular bioeconomy for e-waste management. Finally, it proposes frameworks and procedures to enhance the applicability of the LCA method to future e-waste management research. The literature on the LCA of e-waste management reveals a wide variation in implementing LCA in formal e-waste management, resulting in diverse results and findings in this field. This paper underscores that LCA can pinpoint the environmental hotspots for various pathways of formal e-waste recycling, particularly focusing on metals. It can help address these concerns and achieve greater sustainability in e-waste recycling, especially in pyrometallurgical and hydrometallurgical pathways. The recovery of high-value metals is more environmentally justified compared to other metals. However, biometallurgical pathways remain limited in terms of environmental studies. Despite the potential for recycling e-waste into plastic or glass, there is a dearth of robust background in LCA studies within this sector. This review concludes that LCA can offer valuable insights for decision-making and policy processes on e-waste management, promoting environmentally sound e-waste recycling practices. However, the accuracy of LCA results in e-waste recycling, owing to data requirements, subjectivity, impact category weighting, and other factors, remains debatable, emphasizing the need for more uncertainty analysis in this field.

Resource Recycling, Recovery, and Xenobiotic Remediation from E-wastes Through Biofilm Technology: A Review

Around 50 million tonnes of electronic waste has been generated globally per year, causing an environmental hazard and negative effects on human health, such as infertility and thyroid disorders in adults, endocrine and neurological damage in both animals and humans, and impaired mental and physical development in children. Out of that, only 15% is recycled each year and the remaining is disposed of in a landfill, illegally traded or burned, and treated in a sub-standard way. The processes of recycling are challenged by the presence of brominated flame retardants. The different recycling technologies such as the chemical and mechanical methods have been well studied, while the most promising approach is the biological method. The process of utilizing microbes to decontaminate and degrade a wide range of pollutants into harmless products is known as bioremediation and it is an eco-friendly, cost-effective, and sustainable method. The bioremediation process is significantly aided by biofilm communities attached to electronic waste because they promote substrate bioavailability, metabolite transfer, and cell viability, all of which accelerate bioleaching and biodegradation. Microbes existing in biofilm mode relatable to free-floating planktonic cells are advantageous of bioremediation due to their tolerant ability to environmental stress and pollutants through diverse catabolic pathways. This article discusses the harmful effects of electronic waste and its management using biological strategies especially biofilm-forming communities for resource recovery.

A review on recovery processes of metals from E-waste: A green perspective

E-waste management has become a global concern because of the enormous rise in the rate of end-of-life electrical and electronic equipment's (EEEs). Disposal of waste EEE directly into the environment leads to adverse effects on the environment as well as on human health. For the management of E-waste, numerous studies have been carried out for extracting metals (base, precious, and rare earth) following pyrometallurgy, hydrometallurgy, and biometallurgy. Irrespective of the advantages of these processes, certain limitations still exist with each of these options in terms of their adoption as treatment techniques. Several journal publications regarding the different processes have been made which aids in future research in the field of E-waste management. This review provides a comprehensive summary of the various metal recovery processes (pyrometallurgy, hydrometallurgy, and biometallurgy) from E-waste, along with their advantages and limitations. A bibliometric study based on the published articles using different keywords in Scopus has been provided for a complete idea about E-waste with green technology perspective like bioleaching, biosorption, etc. The present study also focussed on the circular economic approach towards sustainable E-waste management along with its socio-economic aspects and the economic growth of the country. The present study would provide valuable knowledge in understanding E-waste and its different treatment processes to the students, researchers, industrialists, and policymakers of the country.

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.

A critical review of the pre-processing and metals recovery methods from e-wastes

E-wastes being potential sources of numerous valuable metals are promoted to undergo recycling and recovery under the umbrella of urban mining and circular economy. Thus, the present study provides a critical review of the technological details of different metal recycling processes, pre-treatment methods, and the advancements made in these techniques. Critical evaluation of different metal recovery techniques has also been presented based on the available life cycle assessment (LCA), techno-economic, and industrial-scale studies. The study revealed that the integrated metal recovery techniques serve better in terms of recovery efficiency and environmental performance than any single recovery technique. Also, scaling up of biometallurgical, electrochemical, and super critical fluid extraction methods needs to be promoted due to their better environmental performances.

Bioleaching of Typical Electronic Waste-Printed Circuit Boards (WPCBs): A Short Review

The rapid pace of innovations and the frequency of replacement of electrical and electronic equipment has made waste printed circuit boards (WPCB) one of the fastest growing waste streams. The frequency of replacement of equipment can be caused by a limited time of proper functioning and increasing malfunctions. Resource utilization of WPCBs have become some of the most profitable companies in the recycling industry. To facilitate WPCB recycling, several advanced technologies such as pyrometallurgy, hydrometallurgy and biometallurgy have been developed. Bioleaching uses naturally occurring microorganisms and their metabolic products to recover valuable metals, which is a promising technology due to its cost-effectiveness, environmental friendliness, and sustainability. However, there is sparse comprehensive research on WPCB bioleaching. Therefore, in this work, a short review was conducted from the perspective of potential microorganisms, bioleaching mechanisms and parameter optimization. Perspectives on future research directions are also discussed.

Eco-innovations and sustainability in solid waste management: An indian upfront in technological, organizational, start-ups and financial framework

Technological interventions and eco-innovative solutions are necessary to cope with the adverse environmental impacts of waste accumulation. The notion to consider "waste as a resource and recycling of the same for getting the value of the waste" has truly transformed the approach towards solid waste management (SWM). Technological eco-innovations rely on the automation of waste segregation, collection, route optimization, digital apps for creating communication (enhanced efficiency by 40-85%) and treatment technologies. The regulatory framework with amendments in rules, new policies, schemes, smart city missions are responsible for the implementation of "Tech-innovations" at the ground level and has shown societal benefits. India has significantly shown progress in sustainable development goals (SDGs) score from 50.93 to 60.23 (year 2000-2019). The innovative and sustainable waste management practices in India have increased contribution to renewable energy (approx. 2554 MW/annum), 15-billion-USD business opportunity by the circular economy, 25-30% resale profit from processed E-waste, increased co-operative collaborations, trailblazing start-ups, improved SDG 3,7,8,9,11,12,13, improved market for green products and services, brilliant institutional and regional innovations addressing the issue of climate change. The present article critically reviews the exemplary eco-innovations (technological and non-technological) including resource recovery and viable technologies for SWM in India. The review also illustrates the lacunae (in awareness, bioproducts adoption and advanced technologies), recommendations based on findings and future research areas. The paper can also assist researchers, entrepreneurs and the policy makers for improving the status of SWM in India as well as other developing countries with the same societal and economic status.

Nickel and cadmium phytoextraction efficiencies of vetiver and lemongrass grown on Ni-Cd battery waste contaminated soil: A comparative study of linear and nonlinear models

A comparative assessment of the phytoremediation efficiency of two tolerant grass species viz. vetiver and lemongrass were performed in pots against simulated Ni-Cd battery electrolyte waste (EW) contaminated soil (EW1%, EW2% and EW4% w/w). Ni (μg g^-1) accumulation was higher in shoots (36.8) and roots (252.9) of vetiver than in lemongrass (12.5 and 79.7, respectively). While the same trend was true for Cd (μg g^-1) accumulation in vetiver and lemon grass roots (232.2 and 147.2, respectively), however, the accumulation in vetiver shoot (43.4) was less than in lemongrass (99.9). The bioaccumulation factor of metals in both grasses increased with EW contamination. Vetiver was tolerant towards EW toxicity than lemongrass, as it exhibited lesser decline in morphological parameters, lesser rise in TBARS against the doses of EW. The activities of SOD, APX, POD enzymes were higher in vetiver whereas, only GR in lemongrass. Multiple linear regression model show, pH had strong and positive influence over the Ni and Cd uptake by the plants whereas, phosphate, OM and bioavailable metals influenced negatively. The higher R² (>0.9) and Chi-square values ≤ 1 in sigmoid non-linear model demonstrates robustness of the model for predicting the Ni and Cd accumulation (M_HM) in both the grasses. Ni accumulation was higher than Cd, roots had greater accumulation of heavy metal and vetiver was a greater accumulator of Ni and Cd from EW the contaminated soil than lemongrass.

Bioleaching: urban mining option to curb the menace of E-waste challenge

Resource Recovery from Waste Electronics has emerged as one of the most imperative processes due to its pressing challenges all over the world. The Printed Circuit Board (PCB) is one of the typical E-waste components that comprise large varieties of metals and nonmetals. Urban Mining of these metals has received major attention all over the world. The existing treatment procedures used extensively for the resource extraction are hydrometallurgy and pyro-metallurgy and crude recycling practices in the informal sector. However, these methods are prone to cause secondary pollutants with certain drawbacks. Also, the existing informal recycling procedures resulted in insignificant occupational health hazards and severe environmental threats. The application of biotechnology is extensively exploited for metal extraction and emerged as one of the sustainable and eco-friendly tools. However, a limited field-scale study is prevailing in the realm of resource recovery from E-waste using bioleaching method. Hence, the application of bioleaching requires more attention and technical know-how in developing countries to curtail crude practices. The application of bioleaching in E-waste, including its available methods, kinetics mechanism associated opportunities, and barriers, have been discussed in this paper. A glance of E-waste management in India and the menace of 95% crude E-waste recycling are also elaborated. The incentives toward profit, socio-economic, and environmentally sustainable approaches have been delineated based on critical analysis of the available literature.

Acidithiobacillus thiooxidans DSM 26636: An Alternative for the Bioleaching of Metallic Burrs

Metallic wastes from the metal-mechanic industry represent a serious environmental problem. The possible strategies to reduce the metal content of these industrial wastes is their biotreatment by means of sulfur-oxidizing bacteria, such as Acidithioobacillus thiooxidans DSM 26636, which has been reported as an excellent metal-leaching microorganism by its capability to oxide sublimed sulfur and produce sulfuric acid in the presence of metallic burrs, and leach metals. The metallic composition of burrs was determined by ICP-OES before and after its exposure to biological treatment. The bioleaching process was kept for 21 days at 30 °C at an orbital shaking of 150 rev/min by using Erlenmeyer flasks of 125 mL containing 30 mL of Starkey-modified media added with 0.33 g (1% w/v) of sublimed sulfur and 0.33 g (1% w/v) of metal burrs, and 3 mL of inoculum at logarithmic phase. Results showed that A. thiooxidans was able to grow at these conditions with a maximum sulfate production of 11,028 mg/L, sulfuric acid corresponded to 0.16 M, but no statistical difference was observed for days 14 and 21. A reduction in pH was observed from 2.5 to 1.3 units. Metal bioleaching in mg/kg corresponded Fe (4658.5 ± 291), Cr (237 ± 46), Al (185 ± 12), Si (71 ± 10.3), Mo (63 ± 3.6), Mn (46 ± 3.3), V (18 ± 0.94), Mg (22.2 ± 3.7), Ni (15.8 ± 1.5), and Cu (5.7 ± 1.9). Results showed that A. thiooxidans DSM 26636 was able to grow in the presence of metal-containing wastes, and although metal removal was feasible, more studies are needed to enhance metal removal.

Environmental risk assessment of E-waste in developing countries by using the modified-SIRA method

Electronic waste (E-Waste) is a progressively increasing problem for all developing nations. Developing nations like Pakistan, India and China are well renowned for the business of e-waste recycling. With the current rudimentary techniques of recycling used in Pakistan, e-waste presents different risks to the environment and the society with nominal financial gain. The study looks to answer how the e-waste makes its way to Pakistan, what are the risks of the industry and how they affect the population of Pakistan. For this purpose, a method called Modified-Safety Improve Risk Assessment (Modified-SIRA) was used. Modified-SIRA has identified six risks which are a severe hazard to a developing nation such as Pakistan. Each individual risk has been quantified by assigning it with an individually calculated Total Risk Priority Number (TRPN). Furthermore, the risks have been prioritized by the use of Fuzzy-VIseKriterijumska Optimizacija I Kompromisno Resenje (FVIKOR) to assess their impact on the sustainability of the e-waste recycling industry. This study provides evidence that among various risks air pollution from the e-waste recycling process is a severe hazard to the population of a developing country like Pakistan. It further helps to highlight the fact that the population of a developing country tend to ignore e-waste emanating from their expanded use of electronics. Additionally, the present use of rudimentary and non-standardized techniques of material extraction does not possess the capability of sustainably financing the industry. The study further concludes as to which practices and methods can be applied to reduce the impacts and improve the overall sustainability of the industry.

Microorganisms and Plants in the Recovery of Metals from the Printed Circuit Boards of Computers and Cell Phones: A Mini Review

Most electrical and electronic equipment contain a printed circuit board (PCB), which is the board on which microelectronic components are mounted. The PCBs of obsolete and discarded electrical and electronic equipment are a material of great value due to their high metal content that is of commercial importance (i.e., Au, Ag, Pd, Pt, Ir, Ti, Ge, Si, Al, Cu, Ni, Zn, Fe, Sn, As, and Pb). Hydrometallurgical and pyrometallurgical methods have been used to extract metals from PCBs; however, these methods have energy and environmental disadvantages, which is why in recent years sustainable alternatives have been sought. Among these alternatives are the biological methods that contemplate the use of microorganisms and plants to recover metals from PCBs. In this review, only studies specifying the use of bacteria, fungi, and plants in the recovery of metals from the PCBs of computers and cell phones were considered, since the metallic composition of these plates varies according to the electronic equipment. In addition, the challenges and recommendations for these biotechnological processes to be improved and implemented at the industrial level in the coming years are discussed.

Advanced Recovery Techniques for Waste Materials from IT and Telecommunication Equipment Printed Circuit Boards

Waste from information technology (IT) and telecommunication equipment (WITTE) constitutes a significant fraction of waste from electrical and electronic equipment (WEEE). The presence of rare metals and hazardous materials (e.g., heavy metals or flame retardants) makes the necessary recycling procedures difficult and expensive. Important efforts are being made for Waste Printed Circuit Board (WPCB) recycling because, even if they only amount to 5–10% of the WITTE weight, they constitute up to 80% of the recovered value. This paper summarizes the recycling techniques applicable to WPCBs. In the first part, dismantling and mechanical recycling techniques are presented. Within the frame of electro-mechanical separation technology, the chain process of shredding, washing, and sieving, followed by one or a combination of magnetic, eddy current, corona electrostatic, triboelectrostatic, or gravity separation techniques, is presented. The chemical and electrochemical processes are of utmost importance for the fine separation of metals coming from complex equipment such as WPCBs. Thermal recycling techniques such as pyrolysis and thermal treatment are presented as complementary solutions for achieving both an extra separation stage and thermal energy. As the recycling processes of WPCBs require adequate, efficient, and ecological recycling techniques, the aim of this survey is to identify and highlight the most important ones. Due to the high economic value of the resulting raw materials relative to the WPCBs’ weight and composition, their recycling represents both a necessary environmental protection action, as well as an economic opportunity.