11.2.1 Theory of Life Cycle Assessment

LCA is an instrumental methodology to calculate the environmental impacts of goods and services from “cradle to grave” (Hellweg and i Canals 2014). LCA is an internationally standardized methodology to systematically evaluate the environmental performance of a product or process from its origin to the final disposal. LCA can help decision makers better reach their environmental product or service goals through its holistic perspective in quantifying environmental impacts, which has been demonstrated to provide valuable recommendations to identify appropriate solutions for managing solid waste (Hu et al. 2020). To date, LCA has been a very popular analysis tool used in waste management to provide identifying strategies that minimize input–output burdens of products and services on ecosystems, human health, or natural resources.

The concept of LCA emerged in the 1960s, and Coca-Cola was its first user to investigate the influence by replacing all the glass bottles with plastic bottles in the 1970s (Bauman and Tillman 2004). Since then, global scientific awareness of business improvement has called for the development of LCA methodology, and its application in environmental science fields has received much more attention since the 1990s. The current ISO standards 14040 and 14044 describe a general methodology without giving the definite concept name to illustrate this environmental LCA application. Therefore, different names have been used to introduce this concept, such as resource and environment profile analysis (USA), eco-balancing (Germany, Switzerland, Austria, and Japan), environmental profiling and cradle-to-grave assessment (Roy et al. 2009). To spread out the understanding of the complex concept of LCA, The Society of Environmental Toxicology and Chemistry (SETAC) and the US Environmental Protection Agency (USEPA) sponsored a few projects to promote the development of LCI analysis and impact assessment in the 1990s. SETAC Europe and other international organizations, such as the International Organization for Standardization (ISO) and global LCA practitioners, also undertook similar efforts (Roy et al. 2009). Consensus was achieved for an overall LCA framework and a mature inventory development method, which was rapidly involved into a well-known tool for individuals, industries, and policymakers in the environmental science field (ISO 1997). Figure 11.1 shows the stages of an LCA (ISO 2006). The purpose of an LCA can be (i) comparison of alternative products, processes, or services; (ii) comparison of alternative life cycles for a certain product or service; and (iii) identification of promising parts of the life cycle to obtain the greatest improvements (environmental hotspots). There are four crucial steps in conducting a complete LCA assessment: (i) goal definition and scoping; (ii) LCI analysis; (iii) impact assessment; and (iv) interpretation (Roy et al. 2009).

The first step is to set up the goal and scope, which is probably the most important component. The whole LCA study is conducted based on the statement defined in this stage, including the purpose of this study, system boundaries, functional units (FUs) and assumptions, etc. A general input and output flow diagram is commonly used for the scheme illustration within the system boundaries. FUs, usually defined by the mass of the product under study, are used to provide a reference unit for the inventory data to be normalized (Roy et al. 2009; Feng et al. 2020).

LCI analysis is the most intensive step. Due to the complexity of data collection, LCI analysis is known as the most time-consuming and work-intensive step in an LCA. However, if the customers and suppliers are supportive and useful databases are available, the data collection process could be much easier. There are existing databases in LCA software, which usually contains environmental information, including transport, raw materials extraction, material processing, production of used products such as plastic and cardboard, material disposals, etc. For general data such as electricity, coal, or packaging production, the database can be used directly for processes. For product-specific data, site-specific data are required for different processes. In each process, the data should include all the inputs and outputs. Inputs include raw materials, water, energy (renewable and nonrenewable), etc., while outputs include the products and coproducts and emissions to air, water and soil, as well as solid waste generation (Roy et al. 2009; Feng and Hewage 2014).

Impact assessment is the transition step, which aims to understand and evaluate the environmental impacts served by the inventory analysis based on the study’s goal and scope framework. In this phase, the inventory results are assigned to indicate the impact of various expected types on the environment. LCA impact assessment usually comprises four elements: classification, characterization, normalization, and valuation. Classification means assigning and initially aggregating LCI data into common impact groups. Characterization is the process of evaluating the magnitude of each inventory flow’s potential impacts on its corresponding environmental impacts. For example, the potential impacts of methane and carbon dioxide on global warming. Normalization is the process to translate the potential impacts into a way that can be compared, and valuation is the process to measure the relevant importance of environmental impacts by assigning weights, which allows the results to be aggregated further compared with other products (Roy et al. 2009).

Regarding the interpretation, it is the final step of conducting an LCA. An LCA interpretation aims to draw conclusions that can support a decision based on the LCA results. In LCA interpretation, the LCI and impact assessment results are discussed based on the initial goal and scope setup, and the significant environmental impacts are highlighted for conclusions and recommendations. LCA interpretation is a systematic approach to identify, quantify, and evaluate the information based on the LCI and LCIA results, and communicated them effectively. The LCA interpretation might also lead to quantitative or qualitative improvement strategies, such as process and active design, consumer use and waste management, or changes in product. (Roy et al. 2009).

11.3.1 Applications on WEEE Management Strategy

In China, Niu et al. (2012) compared the life cycle environmental impacts of three types of cathode-ray tubes (CRTs) treatment methods: incineration, mechanical dismantling, and manual dismantling. Lu et al. (2014) used sustainability-LCA to evaluate the environmental impacts of two recycling strategies for mobile phone components reuse and recovery. Wang et al. (2014) studied the liquid crystal recovery from LCD panel supercritical and distillation methods and used LCA to analyze this treatment method’s environment impact. Song et al. (2018) analyzed the current CRT TV recycling practice based on the Chinese WEEE Directive and the proposed recycling strategy that includes extended treatment to recover lead from CRT TV, and compared the environmental impacts of two strategies through LCA studies. Yao et al. (2018) applied LCA method to predict the long-term environmental impacts from mobile phone recycling and recommend the optimize mobile phones.

Similar studies have been conducted in Italy. For example, Andreola et al. (2007) explored the CRT glass-based ceramic glaze production vs. standard ceramic glaze production, and assessed the environmental impact of CRT glass recycling strategy through LCA. Compagno et al. (2014) studied the current CRT recycling practices as well as the proposed recycling strategy with metallic lead recovery, and compared their environmental impact differences through standard LCA studies. Amato et al. (2017) also use LCA to measure the environmental impacts of four LCD monitoring treatments: landfill, incineration, traditional recycling, and innovative recycling with indium recovery.

In the UK, Zink et al. (2014) applied smart phones and traditional refurbish smartphones with battery power and solar power into parking meters and evaluated their environmental performance separately through LCA. Alston and Arnold (2011) also analyzed the environmental impacts of plastic mixtures from WEEE (i.e. WEEE plastic) under different recycling rates and calculated the environmental impacts through LCA. The environmental impacts of the treatment systems were assessed as well.

In Japan, Dodbiba et al. (2008) analyzed the recycling strategies of plastic residue from TV sets, and compared the environmental impacts between energy recovery strategy through thermal recycling and material recovery through mechanical recycling. Dodbiba et al. (2012) also explored two liberation methods in a pretreatment system to increase the recovery rate of indium from LCD monitoring and followed with an LCA study to understand the environmental performance.

11.3.2 Applications on WEEE Management System

In China, Song et al. (2013) examined the environmental impact of WEEE recycling systems for various WEEE products. Hong et al. (2015) analyzed formal and informal recycling systems for various WEEE products and used the LCA method to examine each system’s environmental performance. Xue et al. (2015) analyzed treatment systems’ environmental performance for wired printed boards (WPBs). Xiao et al. (2016) explored a variety of WEEE transportation scenarios (labeled S0, S1, S3, S4, and S5) for WEEE management and recycling systems of refrigerators (RFs) in China, and applied environmental assessment to understand if recycling refrigerators could balance with the reclamation processes in terms of emissions.

In Italy, Rocchetti et al. (2013) examined the environmental impact of treatment systems to recover various materials from four types of WEEE residues (i.e. residue from WEEE): fluorescent lamp, CRT, Li-ion accumulator, and PCB. Biganzoli et al. (2015) compared the environmental performance of five WEEE categories by Italian regulations (i.e. R1–R5) in terms of WEEE recycling system. Iannicelli-Zubiani et al. (2017) examined the environmental impact of a treatment system for printed circuit boards (PCBs).

In Belgium, Belboom et al. (2011) established a recycling system for refrigerators and freezers, and compared the environmental impact changes before and after the recycling system. Van Eygen et al. (2016) explored the recycling systems for laptops and desktop computers and calculated each system’s environmental emissions. Tran et al. (2018) conducted an LCA study of a treatment system for batteries from mixed waste, and further merged the LCA method with criticality-based impact assessment (CIAM) method to evaluate the treatment system.

In Brazil, Foelster et al. (2016) compared the environmental impacts of refrigerators recycling systems under different approaches (i.e. informal recycling systems). Campolina et al. (2017) studied a WEEE treatment system for WEEE plastics to produce recycled high-impact polystyrenes (HIPS) pallets and acrylonitrile–butadiene–styrene (ABS) and compared their environmental impacts.

11.3.3 Applications on Hazardous Potential of WEEE Management and Recycling

In China, Song et al. (2015) examined the potential impact on PCB and CRT recycling’s environmental and human health at recycling plants, where LCA methodology was utilized for the evaluation combined with noise assessment and heavy metal risk assessment. In the United States, Lim et al. (2011) combined the LCA method with chemical analysis and hazard assessment models to assess the potential environmental and human health of nine types of light-emitting diodes (LEDs) under two impact categories: resource depletion and toxicity. Hibbert and Ogunseitan (2014) also combined LCA method with chemical analysis and analyzed the potential human health and environmental impacts of ashes from incinerated mobile phones with ecotoxicity impact categories.

In conclusion, LCA is a very useful method and an important decision-support tool to assess a specific product or process’s environmental impacts from its origin to the final disposal. LCA studies have been widely utilized for WEEE management, especially for the recycling of waste electronic products. In Section 11.4 of this chapter, we introduce a case study of cellphones in the Chinese scenario, focusing on LCAs of recycling different types of waste cellphones and common metals contained in them. The purpose of this case study is to illustrate how LCA methodology can elaborate a particular electronic product and assess the environmental impacts of the product from “cradle to grave.”

11.4.1 Goal and Scope Definition

This LCA aimed to quantify the potential environmental impacts of CO₂ emissions from the recycling process of two different types of waste cellphones and common metals in them. A wide range of models and brands of waste cellphones discarded by Chinese consumers were selected. This is because components or materials are varied based on the differentiation of cellphones. The quantified life cycle environmental impacts can provide industry managers with an overall view of the environmental impact of different types of waste mobile phone recycling methods to determine appropriate management methods that have little impact on the environment throughout the life cycle.

11.4.2 Life Cycle Inventory

The data required for each type of cellphone as inputs mainly come from assembly plant and literature reviews. In addition, some inventory data for waste cellphone collection and waste cellphone dismantling were collected from recycling industry reports or recycling enterprises’ official websites. The following sections from 11.4.2.1–11.4.2.7 describe the checklist established for all methods, and the detailed material flows of the two types of cellphone approaches can be found in the supporting file.

11.4.3 Life Cycle Impact Assessment

SimaPro 8.5.0.0™ software was used with the ReCiPe H midpoint method to calculate the global warming potential (GWP) impact. Due to the variety of cellphone data, the LCI analysis data were gathered as interval data. To reduce the data uncertainty, a Monte Carlo simulation (MCS) was applied using Excel. The LCIA results of each process gathered in LCI were analyzed using 10 000 MCS runs. The LCIA results from each MCS run were gathered and are presented in Section 11.4.4.

11.4.4 Results

We developed four distinctive scenarios to present our results. The life cycle environmental impacts generated from these scenarios are presented separately. Waste materials generated in the processing of phone parts or raw materials generated in the telephone recycling process can be reset to recycle the same type of product materials or the same amount of raw materials. Therefore, the influence of the recovery cause is calculated as negative.

11.4.4.1 Feature Phone Formal Collection Scenario

The life cycle environmental impacts of the feature phone (formal scenario) are shown in Figure 11.2. After 10 000 iterations of MCS, the results show that the total CO₂ emissions equal to or less than 0 kg CO₂e are approximately 76%. The cumulative probability of the total greenhouse gas (GHG) emissions in the feature phone (formal scenario) is presented in Figure 11.3. The corresponding impact comprises six parts: the impact from waste feature phone collection, the impact from waste feature phone dismantling, the impact from waste feature phone part recycling, the impact from battery disposal, the impact from metal electronic refining, and the substitution impact from waste feature phone metal recycling.

The results indicate that four processes, namely phone collection, phone dismantling, battery disposal, and metal electronic refining, have positive GHG emissions. In other words, these processes exert negative impacts on the environment. In particular, the metal electronic refining process has the highest impact, followed by the phone dismantling process, which has the second greatest impact. Impacts from phone collection and battery disposal processes are minimal, between 0 and 0.05 kg CO₂e. The other two processes, namely, phone part recycling and phone metal recycling, have negative GHG emissions. In other words, they exert positive impacts on the environment. Particularly, by replacing waste plastic materials and waste screen glasses from waste feature phones, the phone part recycling process can reduce the large amount of GHG emissions, which is more than 0.2 kg CO₂e. Additionally, by substituting metals from waste feature phones, the phone metal recycling process can also reduce the amount of GHG emissions, which hits approximately 0.15 kg CO₂e. In this case, copper, gold, and silver were recycled and substituted for manufacturing.

In summary, regarding phone LCA analysis under the formal scenario, some processes show negative environmental impacts, while other processes indicate positive environmental impacts. Among these processes, the metal electronic refining process has the largest negative environmental impact, and the feature phone, part recycling process, has the highest positive environmental impact.

11.4.4.2 Feature Phone Informal Collection Scenario

The life cycle environmental impacts of the feature phone (informal scenario) are shown in Figure 11.4. After 10 000 iterations of MCS, the results show that the total CO₂ emissions equal to or less than 0 kg CO₂ are approximately 76%. The cumulative probability of the total GHG emissions in the feature phone (informal scenario) is presented in Figure 11.5. The corresponding impact also comprises six parts: the impact from waste feature phone collection, the impact from waste feature phone dismantling, the impact from waste feature phone part recycling, the impact from battery disposal, the impact from metal electronic refining, and the substitution impact from waste feature phone metal recycling.

The results indicate that four processes, namely phone collection, phone dismantling, battery disposal, and metal electronic refining, have positive GHG emissions. In other words, these processes exert negative impacts on the environment. In particular, the metal electronic refining process has the highest impact, followed by the phone dismantling process, which has the second greatest impact. Impacts from phone collection and battery disposal processes are minimal, between 0 and 0.05 kg CO₂e. The other two processes, namely phone part recycling and phone metal recycling, have negative GHG emissions. In other words, they exert positive impacts on the environment. Particularly, by replacing waste plastic materials and waste screen glasses from waste feature phones, the phone part recycling process can reduce the largest amount of GHG emissions, which is more than 0.2 kg CO₂e. Additionally, by substituting metals from waste feature phones, the phone metal recycling process can also reduce the amount of GHG emissions, which hits approximately 0.15 kg CO₂e. In this case, copper, gold, and silver are recycled and substituted.

In summary, LCA analysis of feature phones under informal scenario is very similar to that under formal scenario, except for the impact generated from the waste feature phone collection process, which shows a slight difference between the formal collection process and the informal collection process. It is also noted that some processes have shown negative environmental impacts, while other processes indicate positive environmental impacts. Among these processes, the metal electronic refining process has the highest negative environmental impact, and the feature phone part recycling process has the largest positive environmental impact.

11.4.4.3 Smartphone Formal Collection Scenario

The environmental impact of smartphones on the life cycle (formal scenario) is shown in Figure 11.6. After 10 000 iterations of MCS, the results show that the total CO₂ emissions equal to or less than 0 kg CO₂e are 70%. The cumulative probability of the total GHG emissions on smartphones (formal scenario) is presented in Figure 11.7. The corresponding impact comprises six parts: the impact from waste smartphone collection, the impact from waste smartphone dismantling, the impact from waste smartphone part recycling, the impact from battery disposal, the impact from metal electronic refining, and the substitution impact from waste smartphone metal recycling.

The results indicate that four processes, namely phone collection, phone dismantling, battery disposal and metal electronic refining, have positive GHG emissions. In other words, these mentioned processes exert negative impacts on the environment. In particular, the metal electronic refining process has the largest impact, followed by the phone dismantling process, which has the second greatest impact. The impacts from phone collection and battery disposal processes are similar, and both are very minimal, set between 0.03 and 0.04 kg CO₂e. The other two processes, namely phone part recycling and phone metal recycling, have negative GHG emissions. In other words, they exert positive impacts on the environment. Particularly, by replacing waste plastic materials and waste screen glasses from waste smartphones, the phone part recycling process can reduce the largest amount of GHG emissions, which is more than 0.2 kg CO₂e. Additionally, by substituting metals from waste smartphones, the phone metal recycling process can also reduce GHG emissions, which hits approximately 0.15 kg CO₂e. In this case, copper, gold, and silver were recycled and substituted.

In summary, regarding smartphone LCA analysis under formal scenarios, some processes have shown negative environmental impacts, while other processes indicate positive environmental impacts. Among these processes, the metal electronic refining process has the largest negative environmental impact, and the smartphone part recycling process has the largest positive environmental impact.

11.4.4.4 Smartphone Informal Collection Scenario

The impact of a smartphone’s life cycle on the environment (informal situation) is shown in Figure 11.8. After 10 000 iterations of MCS, the results show that the probability of total CO₂ emissions equal to or less than 0 kg CO₂e is approximately 70%. The cumulative probability of the total GHG emissions in smartphones (informal scenario) is presented in Figure 11.9. The corresponding impact comprises six parts: the impact from waste smartphone collection, the impact from waste smartphone dismantling, the impact from waste smartphone part recycling, the impact from battery disposal, the impact from metal electronic refining, and the substitution impact from waste smartphone metal recycling.

The results indicate that four processes, namely phone collection, phone dismantling, battery disposal, and metal electronic refining, have positive GHG emissions. In other words, these mentioned processes exert negative impacts on the environment. In particular, the metal electronic refining process has the highest impact, followed by the phone dismantling process, which has the second greatest impact. The impacts from phone collection and battery disposal processes are similar, and both are very minimal, set between 0.03 and 0.04 kg CO₂e. The other two processes, namely phone part recycling and phone metal recycling, have negative GHG emissions. In other words, they exert positive impacts on the environment. Particularly, by replacing waste plastic materials and waste screen glasses from waste smartphones, the phone part recycling process can reduce the largest amount of GHG emissions, which is more than 0.2 kg CO₂e. Additionally, by substituting metals from waste smartphones, the phone metal recycling process can also reduce the amount of GHG emissions, which hits approximately 0.15 kg CO₂e. In this case, copper, gold, and silver were recycled and substituted.

In summary, LCA analysis of smartphones under informal scenario is very similar to that under formal scenarios, except for the impact generated from the waste smartphone collection process, which shows a slight difference between the formal collection process and the informal collection process. It is also noted that some processes have shown negative environmental impacts, while other processes indicate positive environmental impacts. Among these processes, the metal electronic refining process always has the largest negative environmental impact, and the smartphone part recycling process always has the highest positive environmental impact.

11.4.5 Discussion

Based on the LCA results, it can be repredicted that the metal electronic refining process always has the highest negative environmental impact in all four scenarios, and the part recycling process always has the greatest positive environmental impact. In addition, the phone dismantling process plays a more important role in smartphone scenarios than in feature phone scenarios since their life cycle environmental impacts are much higher. However, the phone metal recycling process shows a different context; it has a much higher impact in the feature phone scenario than in the smartphone scenario regarding the larger positive environmental impacts. Regarding phone collection and battery disposal processes, relatively similar impact results can be traced in all four scenarios: just between 0.1 and 0.5 kg CO₂e.

The reason for dividing the phone collection process into formal collection and informal collection is that the informal collection approach is actually widely accepted in the Chinese scenario. As the mobile phone weight, metal, and other material content information varies from feature phone and smartphone, we also intend to divide mobile phone types into feature phone and smartphone when we are conducting LCA analysis. Notably, there was only a very slight difference between the formal scenario and the informal scenario, and the impact from the phone collection process in all scenarios was relatively small among all processes. However, in regard to the impact from different mobile phone types, owing to the relatively higher metal content, the metal electronic refining process in waste feature phones actually poses a larger environmental impact than that in waste smartphones, which will significantly increase GHG emissions. Additionally, due to a higher metal content, the substitution impact from waste feature phone metal recycling is larger than that from waste smartphone metal recycling. However, because of the phone weight differences, the impact of waste smartphone part recycling is higher than that of waste feature phone part recycling, significantly reducing GHG emissions. Therefore, future studies should focus on those processes that have a greater impact on the environment. Examples include metal electronic recycling processes and mobile phone dismantling processes.

A great variety of valuable metals are stored in waste mobile phones, including some high-tech metals; in particular, the main high-tech minerals contained in waste feature phones are palladium and cobalt, while waste smartphones mainly contain cobalt, praseodymium, palladium, beryllium, neodymium, antimony, and platinum (Cucchiella et al. 2015; He et al. 2018; He et al. 2021). In this case study, we only considered three common metals, namely copper, gold, and silver. Copper, as an important common metal, has a very high content in waste mobile phones. That is, the impact of refining copper from waste mobile phones would be the greatest among all other metals. In other words, refining copper would cause the most significant environmental impact, which will dramatically increase GHG emissions. For precious metals such as gold or silver, the relative impact of refining them would be much less significant, but they still deserve attention. Future LCA studies should expand the category of metals in waste mobile phones. Expanding the category from precious metals to high-tech metals certainly comes with many challenges. For example, refining one particular type of high-tech metal may cause the loss of another type of high-tech metal. Therefore, it is important to develop a scientific standard on how to refine high-tech metals by sequence, with minimal influence on each other. Additionally, future studies should also combine life cycle cost (LCC) analysis with the LCA method in regard to various high-tech materials in waste mobile phones. From an economic perspective, our previous study indicated that the LCCs of extracting high-tech minerals (HTMs) from one waste feature phone are US$ 6.035 for 1 g of cobalt and US$ 0.014 for 1 g of palladium, while the LCCs of extracting 1 g of cobalt, palladium, antimony, beryllium, neodymium, praseodymium, and platinum from one waste smartphone are US$ 10.106, US$ 0.024, US$ 0.135, US$ 0.005, US$ 0.08, US$ 0.016, and US$ 0.006, respectively (He et al. 2020). Therefore, it is also crucial to investigate the LCAs of recycling high-tech materials from waste mobile phones from an environmental perspective. By combining the LCC and LCA methods, primary data would be available for decision makers or future recycling industry development. In China’s case, the “Regulations on the Recycling of Waste Electrical and Electronic Products” (also known as the China WEEE Directive) was issued in 2009. However, only five main product categories were covered, namely freezer, washer, television, air conditioner, and computer. Until 2016, mobile phones were still included in the latest WEEE management directory (WEEE Catalog 2014). This was the first time that proper recycling management of mobile phones has been required and is subject to legal supervision. Even if the law stipulates that waste mobile phones can only be disposed of by recycling companies officially certified by the government, mobile phone manufacturers and importers must also pay fees to the central WEEE management fund. However, detailed guidelines on how to execute this mandated requirement are still ambiguous. As the results of this case study show that the metal electronic refining process always has the greatest negative environmental impact, it is indispensable to take necessary action to tackle this issue. For example, fund subsidy policies for some major electronic products can potentially be utilized in future mobile phone scenarios. Currently, formal government-certified recycling companies lack the motivation to collect and recycle waste mobile phones, both economically and efficiently. If a detailed mobile phone fund subsidy policy is released, such formal companies would be strongly motivated and begin to collect and recycle waste mobile phones. The metal electronic refining process’s negative environmental impact is likely to be diminished, as these formal companies usually follow strict professional operational procedures.