Advancements and Challenges in Photovoltaic Cell Recycling: A Comprehensive Review
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1. Introduction
In the pursuit of sustainable energy solutions, photovoltaic (PV) technology has become a cornerstone in the transition to renewable power sources. The adoption of solar panels promises reduced carbon footprints and enhanced energy independence. However, a critical challenge lies in the management of end-of-life photovoltaic modules [1].
The global capacity of solar energy installations is growing rapidly, bringing the issue of photovoltaic waste management to the forefront. It is imperative to develop efficient and ecologically responsible recycling approaches to mitigate environmental risks and optimize the longevity of the renewable energy infrastructure [1,2].
The evolution of solar energy is the result of technological breakthroughs and a growing environmental consciousness. Projections show that worldwide cumulative PV capacity is expected to nearly triple (based on the data for 2022), exceeding 2350 GW by 2027 under an optimum scenario. This remarkable growth highlights the unprecedented expansion of solar energy, which is outpacing conventional energy sources at an unprecedented rate [2].
In a transformative development, solar power is set to surpass hydropower as the leading global installed electricity capacity source by 2024 (refer to Figure 1a). Furthermore, solar energy is projected to exceed natural gas by 2026 and coal by 2027, solidifying its position as the dominant contributor to the world’s installed electricity capacity [2].
The global electricity generation landscape is undergoing a transformation, driven by a significant increase in renewable energy sources. Projections indicate that renewable electricity generation will increase by almost 60%, surpassing 12,400 TWh. Although hydropower remains the primary source of renewable electricity generation, its expansion rate lags behind the remarkable growth witnessed in wind and solar PV capacities. Forecasts predict a significant shift, with renewable energy set to surpass coal as the primary source of global electricity generation within the next three years. Renewable energy sources are expected to make up almost 40% of the world’s electricity production by 2027, offsetting the decreasing proportions of coal, natural gas, and nuclear power in the energy mix [2].
Since 2012, the recycling of PV modules has been mandatory in the European Union under the Waste Electrical and Electronic Equipment (WEEE) Directive [3]. This directive outlines specific objectives for the collection, recovery, and recycling of waste from such devices, including PV modules. PV modules are classified as Category 4 ‘Large Equipment’ according to Annex III of the WEEE Directive. As of 2016, a minimum collection rate of 45% is required. Between 2016 and 2019, the collection rate has progressively increased, reaching a minimum of 65% annually from 2019. As of 15 August 2018, new minimum recovery targets have been established for each category. Devices falling under Category 4, including PV modules, are required to achieve an 85% recovery rate and an 80% rate for preparation towards reuse and recycling. The legal landscape regarding PV recycling in the European Union is constantly evolving, with a focus on increasing collection and recovery rates and preparing for reuse and recycling. These directives are part of the EU’s efforts to promote a sustainable circular economy and reduce the ecological impact of electrical and electronic waste, including PV modules. These regulations outline the technical benchmarks and targets established by the European Union to promote efficient recycling of PV modules and sustainable waste management within the electronics industry [3].
Renowned solar PV markets are implementing new policies and targets to increase capacity growth. China led with an impressive addition of 100 GW in 2022, driven by ambitious goals outlined in the 14th Five-Year Plan for Renewable Energy. The European Union responded to the energy crunch in 2022 by accelerating solar PV deployment, achieving a 50% increase to 38 GW in 2022. The REPowerEU Plan and The Green Deal Industrial Plan are expected to be crucial in driving solar PV investment forward. In 2022, the United States implemented substantial funding for solar photovoltaic (PV) through the Inflation Reduction Act (IRA), which provides tax credits to increase capacity and expand the supply chain. India installed 18 GW of solar PV in 2022 and plans to hold annual capacity auctions of 40 GW, with a focus on developing its domestic supply chain. Brazil made significant strides by adding nearly 11 GW of solar PV in 2022, doubling its growth from 2021. Continuous demand from the industry and electricity retailers for renewable energy is expected to sustain this momentum in the medium term [2].
However, in countries experiencing rapid expansion in PV markets, such as China [4], Japan [5], India [6], Australia [7] and the USA [8], specific regulations for end-of-life (EoL) PV modules are still relatively scarce. These nations typically manage PV waste within the broader framework governing hazardous and non-hazardous solid waste or under regulations for Waste Electrical and Electronic Equipment (WEEE), although there are some exceptions. For instance, Japan initiated a “feed-in tariff” [9] in 2012, ensuring fixed rates for electricity generated from renewable sources and exported to the grid, fostering a rapid surge in solar module installations. However, as these installations near their end-of-life (which is typically 20–30 years), Japan is now faced with a significant waste management challenge. In late 2017, the Japan Photovoltaic Energy Association (JPEA) released voluntary guidelines for the proper disposal of end-of-life (EoL) photovoltaic modules. JPEA strongly encourages industry adherence to these guidelines [10], urging manufacturers, importers and distributors to disclose chemical components and collaborate with waste disposal entities [10].
In the USA, certain states exceed the purview of the Resource Conservation and Recovery Act, which regulates hazardous and non-hazardous waste management [8]. California, for instance, has established additional thresholds for hazardous material classification via Senate Bill 489, designating end-of-life PV modules as Universal Waste, streamlining their transportation. This bill awaits approval from the United States Environmental Protection Agency [11].
Australia acknowledges the significance of implementing regulations addressing the issue of PV waste. Officials recognize the importance of ensuring adequate regulatory frameworks to manage PV waste. In a collaborative effort, Victoria leads innovative programs aimed at mitigating environmental impacts across the lifecycle of photovoltaic systems. These initiatives are part of a voluntary industry-led product management arrangement targeting potential risks associated with PV systems and their waste. Additionally, PV modules are catalogued under the National Product Administration Act, signalling intentions to develop a waste management scheme for such products [7].
Based on the complex legal and technical situation described above, there is a need for a structured and analytical discussion of the current situation and future challenges in PV recycling. This review aims to navigate the complex terrain of developments in PV cell recycling, shedding light on the spectrum of methodologies, emerging innovations and inherent complexities that define this central aspect of sustainable energy production. It seeks to dissect the diverse strategies, novel techniques and intricate nuances that underpin the efficient recycling processes that are integral to sustaining the lifecycle of photovoltaic cells within the renewable energy sector.
2. Review Scope and Approach
This review comprehensively examines the recycling options available for photovoltaic modules, with a keen focus on assessing the sustainability of these recycling processes. It delves into the various methodologies currently employed in the industry to recycle PV modules, thereby providing a realistic overview of existing practices and their environmental implications. By exploring both established and emerging recycling techniques, the review aims to highlight the efficiency, challenges, and potential advancements in the recycling of PV materials. Special emphasis is placed on understanding the alignment of these processes with broader sustainability goals. Through this approach, the review seeks to offer valuable insights into the current state of PV module recycling and its contribution to a more sustainable future in solar energy utilization. With a particular emphasis on EU initiatives, this review aims to provide a comprehensive overview of the progress and challenges of PV cell recycling in the context of EU-wide efforts. The review was conducted using various online databases, such as PubMed, Science Direct, Web of Science, Google Scholar and Scopus. The keywords “photovoltaic cell recycling”, “photovoltaic technology”, “waste management”, “development of photovoltaic technology”, “metal recovery”, “recycling of critical raw materials”, “sustainable processes”, etc. were used to narrow down the search. The articles were checked for quality, topicality and relevance based on the journal’s impact factor and cite score as well as the year of publication. During the literature research, the focus was on peer-reviewed journal articles with impact factors according to the “Journal Citation Reports” (JCR) and “Scimago Journal & Country Ranking (SJR) indicator”.
5. Environmental and Economic Aspects
Photovoltaic (PV) recycling is a multi-faceted approach, intertwined with various environmental considerations that are central to sustainable practices within the solar industry [58]. At the core of PV recycling lies the conservation of resources. This process is instrumental in reclaiming valuable materials, such as silicon, glass and metals, from retired solar panels. Recycling significantly reduces the need for fresh resources, making the use of materials more sustainable and efficient. Additionally, diverting used modules from landfills is a crucial aspect of sustainable waste management, substantially mitigating electronic waste accumulation and its associated environmental hazards. Recycling PV modules prevents toxic elements, such as cadmium or lead, from leaking into the environment [59,60]. This curtails potential soil and water contamination, preserving ecosystem integrity. PV recycling has an inherent advantage in its energy-saving capabilities, as the process requires notably less energy than manufacturing new modules from raw materials [46,61]. This aspect highlights a substantial decrease in the carbon footprint linked to conventional manufacturing methods, thus aiding in the mitigation of climate change. Additionally, by appropriately managing hazardous materials during the recycling process, environmental and health hazards associated with improper disposal are minimized [62]. Strong recycling practices guarantee the secure extraction and handling of these substances, reducing the potential harm to both the environment and human health [58,63].
PV recycling is a catalyst for establishing a circular economy within the solar industry. In the context of photovoltaic cell technology, while recycling remains a pivotal aspect due to the complex materials and potentially hazardous components involved, reuse and repair also play crucial roles. Reusing intact PV modules or components that are still functional can conserve resources and reduce energy consumption compared to manufacturing new units from scratch. Additionally, repairing damaged or degraded PV cells can help optimize their performance and extend their operational lifespan, contributing further to resource conservation and waste reduction [64,65].
However, it’s important to recognize that recycling remains indispensable within the broader framework of the circular economy, especially concerning end-of-life PV products. Unlike certain consumer goods, where reuse and repair may be more feasible and economically viable, PV modules often undergo significant degradation over time or become obsolete due to technological advancements. As a result, recycling becomes essential for recovering valuable materials such as silicon, silver and other metals, which can then be reintegrated into new PV cell manufacturing processes [62].
Recycling promotes a more sustainable approach characterised by reusability and resource efficiency by reintegrating recovered materials back into the production cycle [66]. Ongoing research in PV recycling methodologies aims to optimise processes and reduce environmental impacts. This concerted effort ensures that photovoltaic systems maintain a minimal environmental footprint throughout their lifecycle, fostering a more sustainable and eco-friendly solar energy landscape. Solar panels made from recycled materials can vary in quality and efficiency depending on several factors, such as the type and quality of recycled materials used, the recycling process used, and the manufacturing techniques. In general, the quality and efficiency of recycled panels can be comparable to those made from virgin materials when proper recycling methods are used and strict quality control measures are in place. Efforts are ongoing to improve the efficiency and quality of recycled panels through advances in recycling technologies and material selection [61,62].
Photovoltaic recycling has significant economic implications across various dimensions [67]. Recycling PV modules offers a cost-efficient way to recover valuable materials such as silicon, glass and metals [68]. Reusing these materials reduces the need to purchase new resources, contributing to cost savings in manufacturing processes. Several studies have investigated this aspect and demonstrated the economic viability of using recycled materials [50,66,69]. For example, research by [50] conducted a comparative analysis of the production costs of using recycled silicon versus virgin silicon for the manufacture of photovoltaic cells. Their findings indicated that the use of recycled materials resulted in cost savings. In addition, other studies have highlighted the potential for price stability and reduced supply chain risks associated with recycling, further enhancing its economic attractiveness compared to reliance on virgin materials. The establishment and growth of PV recycling facilities also creates job opportunities across different stages of the recycling process [14,61]. Incorporating recycled materials into the production of new PV modules not only has the potential to lower manufacturing costs but also bolsters local economies, fosters innovation, and expertise within the recycling industry [61]. Reusing reclaimed materials, especially those meeting quality standards, can offset expenses linked with procuring raw materials [66]. Mitigating potential fines or penalties can be achieved by adhering to recycling regulations and environmental standards [70]. In countries such as France [51] and Germany [53,54,55], the development of specialised recycling facilities, including those for importing panels for recycling, offers multiple opportunities to improve the local economic landscape. The establishment of such recycling infrastructures not only catalyses job creation, but also cultivates a cadre of skilled workers in the surrounding area. In addition, the recycling sector creates ancillary markets for recovered materials, thereby revitalising local businesses and stimulating innovation in adjacent sectors. In addition, the introduction of community-based recycling programmes plays a key role in promoting environmental sustainability, which in turn increases the region’s attractiveness for investment and wider economic development. Compliance with recycling mandates establishes credibility, fosters positive public perception, and potentially benefits companies in terms of brand reputation and market competitiveness. It is important to note that the use of clear and objective language is crucial in conveying the message of compliance with recycling mandates and Extended Producer Responsibility (EPR) principles. Effective photovoltaic recycling aligns with EPR principles, wherein manufacturers take responsibility for their products throughout their lifecycle [71]. Embracing recycling initiatives enables companies to demonstrate environmental stewardship, potentially enhancing their brand image and consumer trust. Establishing a robust photovoltaic recycling infrastructure reduces dependency on external resource suppliers, contributing to market diversification and resource security [62]. It creates internal loops for materials used in solar panel production, enhancing sustainability and resilience. The integration of photovoltaic recycling aligns with the principles of a circular economy, emphasising resource efficiency and sustainability [63]. By reintegrating materials into the production cycle, PV recycling fosters a more sustainable and self-sufficient industry ecosystem, embodying economic prudence and environmental responsibility. Nevertheless, according to the latest available data, the market share of recycled panels is still relatively small compared to new panels. However, it is growing steadily as awareness of environmental sustainability increases and recycling technologies continue to advance. Exact figures may vary by region and market segment, but the trend is towards increasing use of recycled panels in various applications [72,73].
6. Challenges
The field of photovoltaic (PV) recycling faces several challenges that hinder its widespread adoption and effectiveness. The technological complexity arising from the diverse composition of PV modules is a major challenge. Each module type, such as c-Si, CdTe, CIGS, or a-Si, requires distinct recycling processes, which complicates standardization efforts. Efficiently separating materials and recovering valuable components from PV modules is challenging due to their intricate structure [74]. Achieving high-quality material recovery while minimizing waste and maintaining material purity is a technical challenge. Recycling processes for various PV technologies are still underdeveloped [75]. Although recycling of mono- or multi-crystalline silicon is advanced, other thin films, such as CdTe, have room for improvement [41]. Recycling technologies for newer generation materials are still in early stages [46].
The call for standardized recycling efforts that account for the diversity in module compositions arises from the inherent variability in photovoltaic technologies. PV cells are made from a wide range of materials, including but not limited to, crystalline silicon (c-Si), cadmium telluride (CdTe), copper indium gallium selenide (CIGS), and perovskites. Each of these technologies not only has a distinct light-generating mechanism but also entails different encapsulation materials and manufacturing processes. This diversity results in varied challenges and opportunities in the recycling process. For instance, the recycling process for silicon-based modules, which constitute the majority of the market, is markedly different from that of thin-film modules like CdTe or CIGS. Silicon PV recycling primarily focuses on the recovery of high-purity silicon, glass, and metals like silver and aluminium. In contrast, thin-film module recycling must also address the safe handling and recovery of potentially toxic elements like cadmium in CdTe cells [32,76].
Cost-effectiveness presents a significant hurdle, as the expenses associated with collection, transportation, disassembly and specialized recycling technologies often exceed the value of the recovered materials, making recycling economically less feasible [76,77]. Developing and scaling up efficient recycling infrastructure is a challenge in many regions. The absence of specialised facilities equipped with advanced recycling technologies, combined with the complicated logistics of collecting and transporting used modules, is hindering progress [74]. The management of hazardous materials found in certain PV modules, such as cadmium or lead, requires specialised handling during recycling to reduce environmental and health risks [1]. The lack of consistent and comprehensive regulations or standards tailored to PV recycling complicates the establishment of a cohesive recycling ecosystem. Limited consumer awareness regarding the significance of PV recycling often leads to improper disposal of end-of-life modules [78]. Additionally, the absence of well-established collection systems further complicates efficient collection and sorting. In certain countries, PV residues are excluded from waste legislation due to various factors. Limited research has been conducted on end-of-life (EoL) aspects, primarily due to the lengthy lifespan of new solar modules (25–30 years) [1]. Additionally, the relatively small quantity of this waste compared to other WEEE discourages the establishment of dedicated recycling plants [58]. Defining mandatory EoL treatment requirements also poses an obstacle to efficient recycling processes. Continuous scientific focus on the potential impacts and benefits of treating photovoltaic residues is crucial [79,80].
Globally, only approximately 10% of photovoltaic modules are recycled due to regulatory deficiencies [81]. Currently, recycling silicon-based modules is economically unfavourable as they lack sufficient valuable materials for cost-effective recovery compared to landfilling. However, by 2050, the cumulative recoverable value could exceed USD 15 billion, which would encourage sustainability in the supply chain, energy recovery, reduction in CO2 emissions, and the energy payback time of the solar PV industry [82,83].
Overcoming these challenges will require collaborative efforts among policymakers, industry stakeholders, research entities, and the public. Technological innovation, regulatory support, economic incentives, and heightened public awareness are essential to drive the growth and efficacy of photovoltaic recycling endeavours.
There are some parallels between the development of PV recycling and the recycling of lithium-ion batteries, which is currently a topic of various public debates. Initially, due to the multi-year service life, there was a limited flow of material for recycling. For both areas, the lack of recycling processes was not immediately addressed at the start of production of these high-tech products [75]. When discussing PV modules, it is often compared to other WEEE scrap, and the proportion is declared insignificant [26]. The same comparison can be made for lithium-ion batteries and other battery technologies, such as zinc-carbon batteries. For this reason, the construction of specific recycling plants for PV recycling was previously considered uneconomical. However, this hypothesis has now been refuted due to the quantities of used PV modules that are being recycled. Nevertheless, development is still progressing slowly. A similar situation can also be seen for lithium-ion batteries, although the first recycling plants are currently being built in this area. It is evident that research and development, in particular, have suffered as a result of the low quantities generated in the recycling sector in the first years of the application of the technology. Therefore, there is a corresponding need to catch up.
There is an area of overlap in the costs incurred for recovering value fractions from products. Currently, the costs for recovering valuable materials pose a challenge for developing adequate and high-quality recycling processes. This is because these costs are usually higher than landfill costs [58]. This is partly due to the expectation that larger quantities to be recycled will only be available in the next 3–5 years [84]. These statements apply to both lithium-ion batteries and used PV modules.
Furthermore, legal differences in various regions worldwide pose a significant obstacle. However, in the European Union, overlaps can be identified in future technologies. The European Union mandates a recycling rate of 65% by mass for PV modules [85]. This can be achieved with relatively simple methods, as meeting this requirement is already feasible through the recycling of the glass and aluminium fractions [75]. However, it is important to note that valuable components, such as Si-wafers in PV modules or active material in lithium-ion batteries, are often disregarded in the recycling process. Although recycling the housing and smaller components of the battery may be sufficient to meet the European Union’s prescribed recycling rate of 50% by mass, critical elements such as Co, Ni and Li in the black mass are not always recovered. The New Battery Directive, issued in June 2023, introduces element-specific recycling rates to promote efficient recycling processes for valuable metals [85]. Similar approaches could be considered for PV modules, but specifications are essential due to the diversity of this technology’s composition. One of the key similarities between Si recycling in photovoltaic cells and lithium-ion battery recycling is the importance of resource recovery and material efficiency. Both contain valuable materials that can be recovered and reused, thereby reducing reliance on virgin resources and minimising the environmental impacts associated with extraction and processing. In addition, the challenges associated with recycling both often relate to the complex nature of the materials and the need for effective separation and purification techniques. Studies focusing on one process can provide transferable knowledge and methodologies that can be applied to the other, facilitating advances in recycling technologies for both. Furthermore, given the increasing demand for both photovoltaic cells and lithium-ion batteries in the renewable energy and electric vehicle sectors, synergistic approaches to recycling could lead to enhanced resource recovery and improved circular economy practices. Collaborative research efforts that bridge the gap between PV recycling and lithium ion battery recycling can foster innovation and accelerate the development of sustainable recycling strategies for both sectors. In conclusion, exploring the links between PV recycling processes and LIB recycling can indeed provide valuable insights and contribute to the strategic development of recycling methodologies for both processes. By exploiting similarities and sharing knowledge across disciplines, researchers and industry stakeholders can work towards more efficient and sustainable recycling practices, ultimately contributing to the transition towards a circular economy.
Raising consumer awareness is crucial to increasing the uptake and support of photovoltaic (PV) cell recycling initiatives as well as for the save collection of used lithium ion batteries. Educational campaigns targeting both the general public and specific consumer segments should be included. This could include outreach through various channels such as social media, educational workshops and collaboration with environmental organisations. By highlighting the environmental benefits and long-term cost savings associated with PV cell recycling, consumers can be incentivised to choose environmentally friendly options and properly dispose of end-of-life solar panels.
Engaging stakeholders across the PV industry value chain is essential to foster collaboration and advance recycling efforts. Platforms between manufacturers, policy makers, recyclers and research institutions should be established for dialogue and collaboration. Promoting industry-wide initiatives, such as voluntary recycling programmes or incentives for sustainable practices, can drive collective action and innovation. In addition, fostering partnerships with academia and government agencies can facilitate knowledge sharing and the development of standardised recycling practices.
Cost reduction strategies are key to improving the economic viability of PV cell recycling. Focusing on technological innovation, economies of scale and regulatory incentives, a multi-faceted approach should be sensitive. Investment in research and development to optimise recycling processes and develop cost-effective technologies can reduce operating costs. Promoting economies of scale through centralised recycling facilities or collaborative networks can also increase efficiency and reduce unit costs. In addition, implementing policies such as Extended Producer Responsibility (EPR) frameworks or tax incentives for recycling can create financial incentives for manufacturers to invest in sustainable practices.
By addressing these key areas, research and industry will be able to drive the development of PV cell recycling towards a more sustainable and economically viable future.
7. Conclusions and Outlook
A thorough examination of current and developing technologies in the photovoltaic field revealed the complex variety of PV module types, including crystalline silicon (c-Si), cadmium telluride (CdTe), copper indium gallium selenide (CIGS), and amorphous silicon (a-Si). Each type requires specific recycling strategies due to their unique compositions and materials. Strategies for PV recycling include disassembly, material separation, and recovery techniques, as well as reintroducing reclaimed materials into production cycles.
The economic potential and environmental benefits of PV recycling are significant, as material reclamation reduces manufacturing costs and fosters resource conservation, waste reduction, and energy efficiency. Economically, the focus is on cost savings, job creation, compliance advantages, market diversification, and integration with the circular economy. Environmentally, the emphasis is on resource conservation, waste reduction, energy efficiency, and responsible hazardous material management, all aligned with sustainability objectives.
The seamless adoption and efficacy of PV recycling face numerous challenges. Significant hurdles have been identified in the recycling of PVs, including technological complexities in material separation, cost-effectiveness, deficient recycling infrastructure, management of hazardous materials, regulatory frameworks, and limited consumer awareness and collection systems.
However, ongoing technological advancements and research efforts are promising to overcome these challenges and enhance the cost-effectiveness of PV recycling. Collaborative efforts among stakeholders are pivotal in establishing robust recycling infrastructure and standardized regulations. To streamline recycling processes, it is important to augment consumer awareness and fortify collection systems. These endeavours are guided by the circular economy framework, which strives towards resource efficiency and sustainability.
In conclusion, the efficient and environmentally responsible future of PV recycling requires concerted efforts from stakeholders across industries, policymakers, researchers, and the public. It is necessary to tackle challenges, refine strategies, and foster a sustainable and circular approach.
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