Waste LEDs in China: Generation estimation and potential recycling benefits
Graphical abstract
Introduction
The current electricity sector is carbon-intensive, contributing heavily to global climate change and environmental problems (Kis et al., 2018). In China, massive greenhouse gas emissions produced by fuel- and carbon-intensive power generation also negatively impact the environment (Ding et al., 2017). According to statistics, China consumed 724.66 billion kWh of lighting power in 2013, accounting for 14.15% of all social power consumption (Zheng et al., 2016). Switching to light emitting diode (LED) devices can reduce electricity consumption and greenhouse gas emissions significantly (Hicks et al., 2020; Khorasanizadeh et al., 2015), which will bring about considerable economic and environmental benefits (Welz et al., 2011). Besides, the costs of LEDs are continually decreasing by 28% to 44% each year due to technological advancements (Kim and Brown, 2019; Mizanur Rahman et al., 2017). These factors contribute to the rapid market expansion of LED technologies, which then leads to waste LEDs one of the fastest growing and most challenging e-waste streams (Cenci et al., 2020a; Pourhossein et al., 2022).
The effective management of waste LEDs should be a high priority from both an environmental and a resource perspective (Fang et al., 2018). On the one hand, waste LEDs contain hazardous elements such as arsenic and lead (Lim et al., 2013), as well as various brominated flame retardants, which will seriously pollute the environment and threaten human health if not properly treated (Pourhossein and Mousavi, 2018; Kumar et al., 2019; Zamprogno Rebello et al., 2020). On the other hand, compared to natural ores, the concentration of gold, silver, copper, aluminum, tin, gallium, and other valuable elements in waste LEDs is even higher (Cenci et al., 2020b). As the total volume of waste LEDs becomes larger, urban mining is increasingly a potential option to alleviate the worldwide metal shortage (de Oliveira et al., 2021; Pourhossein et al., 2022). For example, the annual growth rate of global demand for rare earth elements (REEs) is 3.7% to 8.6% (Tan et al., 2015). The risks in their regional supply (Althaf et al., 2019; Du and Graedel, 2011; Işıldar et al., 2018) can be mitigated by REEs contained in fluorescent powders (Qiu and Suh, 2019) and other components of waste LEDs (Liu and Keoleian, 2020).
China's National Development and Reform Commission published “The 14th Five-Year Plan for Circular Economy Development”, proposing a complete resource recycling industrial system by 2025 (NDRC, 2021). Given the massive resources contained in waste LEDs as mentioned previously, the resource benefits of recycling will be significant compared to other waste disposal methods such as incineration and landfills (Andooz et al., 2022). Besides, the substitution of recycling for incineration and landfills contributes to mitigating the environmental and health impacts (Pourhossein and Mousavi, 2018). First, after being landfilled, hazardous elements contained in waste LEDs can harm human health and cause secondary pollution in the form of landfill leachate (Mizanur Rahman et al., 2021). Second, due to the presence of brominated flame retardants and other substances, incineration produces harmful emissions such as dioxins and furans, which have irreversible effects on human health (Kaya, 2016). Finally, the waste LED devices show great recyclability and criticality from the economic and technical perspective (Fang et al., 2018). Overall, the presence of hazardous, strategic, valuable materials in discarded LED devices makes their recycling critical (Martins et al., 2020; Mizanur Rahman et al., 2017).
To avoid hazardous waste, resource depletion, and ecological/health risks, recycling will necessary (Lim et al., 2011; Mizanur Rahman et al., 2017). Against this background, studies on the (potential) economic feasibility of recycling are emerging (de Oliveira et al., 2021). Annoni et al. (2020), for instance, quantified the potential for recycling metals from surface-mounted-device (SMD) LEDs through hydrometallurgy and membrane separation, showing high concentrations of metals. Especially, the existence of gold and copper, as well as the reuse of acid, indicated the potential for economically feasible recycling. Similarly, Zamprogno Rebello et al. (2020) characterized the composition of a representative LED device sample. Results show that in addition to the environmental imperative due to arsenic, the presence of precious metals and REEs (cerium and yttrium) in LED devices make recycling economically attractive. Compared with natural ores, the concentrations of precious metals (gold and silver) in waste LEDs are commonly found much higher, which are of great economic interest (Cenci et al., 2020b, 2020a). Besides, for some critical metals and REEs contained in waste LEDs, which are irreplaceable in low-carbon technologies and with supply risk, the low grade of nature ores and difficulty of primary extraction gives recycling its appeal (USGS, 2020, USGS, 2019). With the development of bioleaching (Pourhossein et al., 2022), separation and purification technologies (Cenci et al., 2021), and reagent reuse (Annoni et al., 2020), waste LEDs with higher gallium and REE concentrations may be cost-effective compared to primary sources.
In the near future, waste LED devices may become a major global issue (Cenci et al., 2020b). In China, with the further substitution of LED technologies for other traditional lighting devices, the stockholders along the recycling chain should be prepared for managing massive waste LEDs effectively. Despite it, circular economy policies and collection systems are still lagging, largely due to a fragmented understanding of waste LED generation trends, as well as the economic and environmental benefits of the substitution of recycling for other waste disposal options. Recent studies have examined the economic and environmental benefits of recycling waste LEDs at the national level. The potential benefits of metal recycling for LEDs in Canada (Kumar et al., 2019) and Greece (Grigoropoulos et al., 2020), for instance, have been estimated in terms of economy and the environment. These estimates can provide valuable knowledge that can facilitate the selection of appropriate and stage-feasible circular economy actions by local stakeholders. In China, however, there is still a lack of such research.
The existing research fails to provide sufficient insights into China's recycling practices, potentially resulting in the mismanagement of waste LEDs. The purpose of this study is to highlight the growing in-use stock and waste generation of LEDs in China, as well as the potential benefits of recycling in terms of the economy and the environment, thereby raising public awareness and guiding real-world practice. Specifically, Holt's method is conducted to predict the short-term trends of LED sales in six application fields (Holt, 2004; Islam and Huda, 2019). Then, the market supply A model (Li et al., 2015) and Weibull distribution model (Melo, 1999; Wang et al., 2013) are used to estimate the in-use stock and waste generation of LEDs. Finally, we discuss the potential economic and environmental benefits of recycling in the context of various scenarios. It is expected that the results of our study will provide a reference point for the development of viable circular economy policies, and inform the waste LED recycling industry.
Section snippets
Scope of research
LEDs used in the general lighting, landscape lighting, display, backlight application, signals and instructions, car lighting, and other fields are taken as the research objects. General lighting, which includes residential and commercial lighting, is the most widely used area for LEDs. This paper provides an estimation of waste LED generation in mainland China from 2012 to 2025. The research period is set since 2012 as the penetration rate of LEDs in China was less than 1% before that year.
Sales of LEDs
LED sales in different application fields from 2012 to 2025 are derived by combining the historical data (China Solid State Lighting Alliance, 2019, China Solid State Lighting Alliance, 2018, China Solid State Lighting Alliance, 2017, China Solid State Lighting Alliance, 2016, China Solid State Lighting Alliance, 2015, China Solid State Lighting Alliance, 2014, China Solid State Lighting Alliance, 2013) and forecast results based on Holt's method (Holt, 2004; Islam and Huda, 2019) (Fig. 2). The
Conclusion and implications
With the popularity and maturity of LED technologies, end-of-life management will play an increasingly prominent role in climate change mitigation, heavy metal pollution reduction, and resource conversation. This paper quantifies the in-use stock and waste generation of LEDs in different sectors in China for the first time. According to the characteristics of LEDs, this paper combines Holt's method, the market supply A model, and the two-parameter Weibull distribution to obtain more accurate
CRediT authorship contribution statement
Xi Tian: Writing – original draft, Supervision, Conceptualization, Methodology, Validation, Project administration, Funding acquisition. Jinliang Xie: Writing – original draft, Visualization, Conceptualization, Methodology, Investigation. Lei Hu: Writing – original draft, Methodology, Visualization, Investigation, Data curation. He Xiao: Visualization, Validation, Investigation. Yaobin Liu: Writing – review & editing, Conceptualization, Validation, Investigation.
Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
The authors gratefully acknowledge the financial support of the National Natural Science Foundation of China (52060017), the Major projects of the National Social Science Fund of China (18ZDA047), and the Jiangxi Social Science Foundation (21ST06). Thanks to Ziqian Xia for his contributions in data analysis and visualization.
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