Scientometric Analysis of Research on End-of- life Electronic Waste and Electric Vehicle Battery Waste

Electronic sector is the one of the most rapid developing sector which is also contributing towards uncontrolled handling of waste flows. It not only poses threat to environment but also to public health due to adoption of improper recycling and disposal methods. One of the fastest classified branch of e-waste which has potential to grow in future is end-of-life electric vehicle batteries. This paper presents current body of literature available on two giant data bases i.e. Scopus and Web of Science, focussing on research on environmental impact of e-waste and electric vehicle battery waste. For this purpose two set of keywords are used: Set A (Generalised) -“Environmental Impact of Electronic waste having 1498 research documents on Scopus and 1009 on Web of Science and Set B (Specific) “Environmental Impact of Electric Vehicle Battery waste” having only 85 and 64 research documents on Scopus and Web of Science respectively. USA, China and Germany are having max imum funded projects. The developing countries, lag behind drastically in terms of funded projects. This scientometric study thus draws the attention towards the urgent need of research in this area in order to minimize the resource depletion and maximize the sustainability.


INTRODUCTION
The generation of e-waste is increasing exponentially with recent developments in IT sector and overall increase in demand of computers, laptops, mobile phone, washing machines, TVs and electric cars, electric busses, e-bikes etc. Also, the automobile sector will be flooded with electrical vehicles in large volume to curb air pollution and noise pollution but will again add to the quantum of e-waste generation per capita. In 2018, the global electric car fleet exceeded 5.1 million, up 2 million from the previous year and almost doubling the number of new electric car registrations, electric two/threewheelers on the road exceeded 300 million by the end of 2018. Electric buses continued to witness dynamic developments, with more than 460 000 vehicles on the world's road, almost 100000 more than in 2017 (IEA, Global Annual Report on Electrical Vehicles, 2019). The People's Republic of China (hereafter "China") remained the world's largest electric car market, followed by Europe and the United States. Norway was the global leader in terms of electric car market share (46%). The global stock of electric two-wheelers was 260 million by the end of 2018 and there were 460 000 electric buses. In freight transport, electric vehicles (EVs) were mostly deployed as light-commercial vehicles (LCVs), which reached 250 000 units in 2018, while medium electric truck sales were in the range of 1 000-2 000 in 2018. In India a programme named FAME (faster adoption of manufacturing of electric vehicles) was launched by government in two phases i.e. phase I and II which aims in production and manufacturing of electric 4-wheeler, 3-wheeler, 2-wheeler and electric buses. These electric vehicles are loaded with batteries made up of Lithium-Ion and Lithium-polymer, due to their high energy per unit mass and charging capability. Lithium Ion battery is composed of few undesirable metals like graphite (16%), Cu (9%), Ni (4.3%), Ag (20.2%), Polymer (14%), Al (5.5%), and Electrolyte (3.5%) [1,2] convey the presence of Pb (33.1 mg/l), Cr (6.14 mg/l) Th (7.86), Co (278000 mg/l), Ni (2960 mg/l). Once these batteries go out of use, they should preferably reused, reduced and recycled.
It is not possible to recycle Lithium-Ion Batteries without causing any Environmental Impact. [3] In Country like Australia, 98.3% of Lithium-ion portable batteries are landfilled. [4] The actual scenario of recycling and disposal of such waste product and their fate is still to be researched in extensive manner all over the world. To research in this area, a bibliometric survey is performed from two of the giant databases i.e. Scopus and Web of Science which enable us to evaluate the need of doing research on this particular problem along with existing research being done. There are few key points taken into consideration to generate the data analysis. The search analysis, for a set of generalized keyword result and specific keyword result, is been compared and presented. The paper focuses on bringing all related analysis and comparisons to bring an insight on literature review available with us in Scopus and Web of Science (the data used, are taken on 24 th of Sep, 2020). Figure 1 shows the flow chart of the Scientometric study performed and the various analysis done.

Source
The Scopus and Web of Science are one of the most giant data bases for research documents. Analysing any research area on these two data bases can provide a clear picture of research background pertaining to a particular domain. Various research collaborators, institutes and funding agencies could also be known through analysing the various searches on both the data bases. The first research document in the area of environmental impact of electronic waste appeared first in the year of 1973 and 1986 in Scopus and Web of Science respectively. Whereas research documents on environmental impact of electric vehicle battery waste appeared first in the year of 1988 and 1986 in Scopus and Web of Science respectively.

Keywords: Selection
There are two keywords taken into consideration. One is generalised set of keywords i.e. "Environmental Impact of Electronic waste"-Set A whereas the other one is based on Environmental impact of one of the type of e-waste i.e "Environmental impact of electric vehicle battery waste"-Set B. Table 1

Keywords
Search Results

Scopus Web of Science
Environmental and impact and of and electronic and waste -Set A 1510 1011 Environmental and Impact and of and electric and vehicle and battery and Waste-Set B 85 64 Environmental and impact and of and electronic and waste and flows 147 79 Environmental and impact and of and electric and vehicle and battery and waste and flows -14 5

B. Language
More than 95% documents for both the set of keywords in both the data bases are in English language. There are few documents in Chinese language as well followed by French, Portuguese, and Spanish as Table 3.

C. Source Type
There are various sources of publication of documents in Scopus and WOS for set A and B. Most of the documents are either published as articles or as review paper followed by conference paper, editorial board etc. for Set A in both the data bases. For set B, most of the documents are published as articles and review paper in both the data set. There is no conference paper document till date for set B in WOS database as shown in Figure 2 and 3.
decreasing order. For set B, the predominant research areas in scopus are: Environmental Science and Ecology, Energy fuels, Science and technology, chemistry, computer science, telecommunications, business economics, electrochemistry, material sciences etc. as Figure 5. Public environment occupation has 13% weightage for set A i.e. environmental impact of e-waste and the main reason of this subject area is due to the fact that illegal recycling market has caused occupational hazard and human health impacts. Since, Electric vehicle batteries, it recycling and probable occupational hazard which it can cause is till unexplored area, hence public environment occupation is not a subject area for set B.

Geographical Analysis
The satellite images are obtained by using Goggle i-map creator software as shown in Figure 6 (a) and (b) so as predict about countries which are already working on the topics with set A and set B respectively from database of Scopus. The number of countries and the corresponding number of documents which they have produced in much higher in

D. Subject Areas
In data base of Scopus, the main subject areas for set A are environmental sciences, engineering, energy, business management, chemistry, material sciences, chemical engineering and so on ( Figure 4) and same subject areas are contributing areas for set B as well. The variation is only in terms of percentage total contributed by each subject area i.e. engineering science contributes 39% of the total value for set A while, 28% for set B.
The data base of web of science depicts that for set A, the contributing areas are environment science ecology, engineering, public environmental occupation, business economics, energy fuels, toxicology and so on in the

Bibliographic coupling using clustering
Bibliometric coupling depicts the number of scientific papers which poses meaningful relation with each other. There are various categories on which bibliographic coupling can be performed such as for documents, authors, countries, sources etc. In the present study, bibliometric coupling of documents and authors is been considered for both the keyword sets (Set A and B) in scopus. There are few terms such as network, node, cluster, link strength and total link strength to understand bibliometric coupling analysis and citation analysis. Network consists of several node and a cluster is a set of closely related node. Every node in a network is assigned to exactly one cluster. VOS software uses colours to indicate the cluster to which node has been assigned. Link strength indicates the number of items cited to the selected node, whereas total link strength represents a number of times a document is cited by links strengths. Premalathe m. et al. [5] having their document in critical review in env. Science technology, 44 (14) has 584 links having 3146 of total link strength and 52 citations.

i) Documents
The analysis was made on VOS software by setting the search as weights: Total link strength and Scores: Citations. Bibliometric coupling of document produced by Fan E. et al. [6] is having 37 links having 195 as total link strength and total 9 citations till date.
by others. It is one of the most important parameters of a bibliometric analysis. In the present study, citation analysis is done for both the set of keywords.

Citation Analysis using clustering
Citation analysis is done to study the impact and assumed quality of an article, an author, or an institution based on the number of times works and/or authors have been cited

Research Implication of the Study
The increase in volume of EV has two major implication, a) Over consumption of Lithium -Ion, thus demanding endof-life assessment b) Generation of battery waste through end -user. Hence it becomes very important to work on the solution of these two problems associated with lithiumion batteries. This paper presents a wide range of statistics available on two giant databases: scopus and web of science. By analysing the two different set of keywords combinations (Set A and Set B), it becomes clear to the researchers, which part is still to be researched and left unexplored. The main purpose of this bibliometric survey is to produce statistical data analysis so as to reflect the level of research work already been done in this area, about the people who already have contributed and thus the researchers can accordingly decide the area in particular based on the research theme and can also connect with those who are already working in this area for better exposure. With bibliographic coupling and citation analysis, many connecting nodes becomes clear as which countries are most actively researching on electric vehicle battery waste and which are yet to start their propagation in this alarming issue of waste generation and management. Apart from this, through network analysis various authors, sources and organisations it becomes very much useful for upcoming researchers to use their experience in terms of knowledge and experience sharing or having future research collaborations which could be beneficial for the society and sustainable development. The impact of perpetual growth in e-waste and electric vehicle battery waste would ultimately affect not only the human health and environment but also the ecosystem. Few of the researchers have shown through their research how it may cause adverse impacts overall. It thus becomes important to address few geo-environmental concerns of e-waste as well as EV battery waste so as to bring awareness of this issue of concern amongst researcher, scientist and engineer's community and be able to generate solution to this problem.

Impact of E-waste and EV battery waste on human health, environment and ecosystem
Every year 20 million to 50 million metric tons of e-waste is generated as per an estimate by United Nation and only 20-25% of that are recycled formally in Asian and African countries. [7] Despite of the Basel convection, the developed nations are exporting their e-waste to developing nations. [8] Developing countries are generating secondary source of income through illegal recycling of e-waste. The e-waste due to uncontrolled landfilling and recycling has affected the overall environment adversely and the various impacts are discussed in this particular section. Table 4 shows  the various keyword combinations and its corresponding number of Scopus and WOS documents considering classification of impact of e-waste and EV battery waste on environment, human health and ecosystem. It can be seen from the table that the number of documents on EV battery waste is very less in comparison to number of documents on electronic waste. There are only 33 Scopus and 18 WOS documents on "Impact of EV battery waste on Environment" and 378 Scopus and 250 WOS documents are there on "Impact of Electronic waste on Environment". Similarly, the number of documents for impact on ecosystem, soil, air quality and human health is shown for electronic waste and EV battery waste, in order to draw further comparison statistically.
The recycling activities of e-waste can cause surface soil pollution by heavy metals. [9,10] In Bangalore, India few soil samples were collected from a e-waste recycling slum and the level of heavy metals crossed the regulatory threshold limit (2850 mg/kg Pb, 39 mg/kg Cd, 4.6 mg/kg In, 180 mg/ kg Sb, 957 mg/kg Sn, 49 mg/kg Hg, and 2.7 mg/kg Bi) in comparison to nearby control sites of the same city. [11] The problem lies in the fact that the roots of the plants can easily absorb such harmful metals from the underlying contaminated soil and while growing these heavy metals can be transported to stem and leaf, which has chances of consumption by human or animals. [12] Thus, it has tendency to effect the whole food chain [13] analysed the impacts of heavy metals contained in e-waste on soil through experimentation and results show that it renders the soil sterile and alters its microstructure.
In many developing countries crude technology is adopted for the recycling of e-waste in which the recycling by-products are directly disposed of in the environment. [14,15] The e-waste contamination has affected the aquatic life as well. The environment wherein e-waste is disposed of is difficult for the survival of fishes and thus, such contamination is considered as a threat to wild fishes. [16] The pregnant women living near to such recycling sites are hard to barricade themselves from the exposure of heavy metals and organic pollutions, which has led to an increased possibility of premature births, reduced birth weights and infant lengths, spontaneous abortions and still births. [17,18] A study was carried out in china to know the effect of e-waste burning/ recycling on the air quality and it was found to have high mean concentrations of particulate matter (100-243.310 ± 22.729 μg/m3) and PoPs). [19] EV battery contributes maximum to e-waste contamination and is a potential source of hazardous metal pollutants (Co, Cu, Ni, Pb) and is most likely to impact environment and human health. [2] There are different EV battery chemistries available and there is not much research available on how different types of LiBs leach under landfill condition. [20] There is a need of increased coordination of the regulatory policies in order to reduce the levels of hazardous chemical components by adopting improved recycling techniques.

Confines of the Present Study
This bibliometric survey thus brings an insight on statistics available on scopus and web of science for the environmental impact of lithium ion batteries and its end-of-life analysis. There are many bibliometric parameters considered to carry out this survey.
The following points discusses the summary of bibliometric study:

CONCLUSION
The increase in demand of electric vehicles has resulted in increased use of lithium ion batteries. The end of life lithium ion batteries would contribute to a huge quantum of ewaste. It thus becomes very important research in the area of environmental impact of these end of life lithium ion batteries also it is important to research in the field of proper and sufficient recycling facilities for sustainable use of lithium and other metals present in end of life lithium ion batteries. The paper presents bibliometric analysis of research in the area of environmental impact of electronic waste (Set A) and Electric Vehicle battery waste (Set B). The statistics of research work done in this area till date which clearly indicates that the work done is very less in terms of research for impact of lithium ion on environment. There are only 85 research works published in Scopus till date and 28 in web of science, majorly in developed nations for environmental impact of lithium ion batteries. It is evident from the analysis of data that, in developing countries the area is almost unexplored while the problem is predominant. The analysis also revealed that there is a lot of scope for researchers to bring the solution towards end-oflife of lithium-ion battery waste as the manufacturing demand is going to increase immensely and thus, recycling will be the only solution to encourage the sustainable development.
There are scientists/researchers from USA and China who are working in development of recycling techniques which states that the other counties like India, Japan, Australia which are going to witness the increase in number of electric vehicle in coming years significantly must start working towards finding the solution to this issue for the benefit of the society, environment and sustainable development.