Toxicity assessment and feasible recycling process for amorphous silicon and CIS waste photovoltaic panels

A review of toxicity assessment procedures of solar photovoltaic modules

Environmental management of solar photovoltaic (PV) modules is attracting attention as a growing number of field-operated PV modules approach end of life (EoL). PV modules may contain small amounts of toxic metals, and the procedures for assessing and regulating the toxic metal content and release of such materials at EoL differ widely across nations. This paper provides an overview of the metal composition of PV modules and common procedures for toxicity assessment through extensive research and review of technical literature and legislative documents. This review focuses on three primary aspects: first, it explores the distribution of toxic elements within current and emerging PV module designs, with a specific focus on obtaining representative samples for proportional toxicity testing within different module laminate areas. Second, it examines a sampling standard and the diverse toxicity testing methods and regulations employed in various regions, encompassing standards like the Environmental Protection Agency (EPA) Test Method 1311 (Toxicity Characteristic Leaching Procedure, TCLP) in the U.S., Restriction of Hazardous Substances (RoHS) in Europe, and the Waste Extraction Test (WET) in California. Third, the review examines the sources of variability in toxicity testing outcomes, including techniques for securing homogeneous samples from non-uniform PV modules, selecting particle sizes representative of landfill conditions in extracted samples, determining appropriate leachate characteristics such as leaching agents and pH levels, and considering factors like test duration and temperatures. In summary, this review summarizes relevant regulations and offers a comprehensive overview of the strengths and limitations associated with several toxicity assessment procedures currently in practice.

Strategic overview of management of future solar photovoltaic panel waste generation in the Indian context

Solar energy has become a leading solution to meet the increasing energy demand of growing populations. Solar photovoltaic technology is an efficient option to generate electricity from solar energy and mitigate climate change. Although the development and growth of solar photovoltaics has had a positive impact on energy system decarbonization, but end-of-life solar panels might become toxic waste if not properly disposed of. Presently in India, approximately 200,000 tonnes of solar photovoltaic waste are expected to be produced by 2030 and 1.8 million tonnes by 2050, by which time solar waste could grow to 60 million tonnes globally. Solar waste has recently been included in the category of waste electrical and electronic equipment to restrict the negative influence of continual development. Recent advancements have been focused only on increasing the efficiency of solar photovoltaic panels without considering the impact of waste solar panels on the environment and the issue of appropriate disposal of waste panels. Effective and ecofriendly methods for recycling end-of-life waste are rarely considered. There is a need to critically investigate and manage the disposal and recycling of solar panels waste. This review article addresses handling and recycling of solar waste, which will be present in large quantities after 25 years. We review multiple adopted technologies to recycle solar waste and technological advancement achieved while recycling photovoltaic waste. Further life cycle assessment of recycling technologies is also discussed.

Analysis of the Photovoltaic Waste-Recycling Process in Polish Conditions—A Short Review

The rapid development of the photovoltaic (PV) industry is determined by subsequent legal documents and directives, which indicate the need to use renewable energy sources in order to counteract climate pollution and strive to increase energy efficiency. The development of the photovoltaic industry in the near future will result in an increase in the amount of electrical and electronic waste from used photovoltaic panels. The total installed capacity of photovoltaic sources in Poland at the end of 2019 was almost 1500 MW, and in May 2020, it exceeded 1950 MW, and the weight of the installation was approximately 120,000 tons. The aim of the present work is to present the types of materials used in the construction of photovoltaic panels, with particular emphasis on the possibility of recycling or utilization of individual elements. Additionally, the aim of the work is to describe the most important requirements addressed to the members of the European Union, which were formulated in the provisions of Directive 2012/19/EU. Taking into account the number of photovoltaic panels produced in Poland, the possibility of recycling individual materials from PV assembly was analyzed. The author presents the problem of recycling in the combination of legal and material aspects, which will soon become the share of Poland as a member of the European Union.

Reshaping the Module: The Path to Comprehensive Photovoltaic Panel Recycling

The market for photovoltaic modules is expanding rapidly, with more than 500 GW installed capacity. Consequently, there is an urgent need to prepare for the comprehensive recycling of end-of-life solar modules. Crystalline silicon remains the primary photovoltaic technology, with CdTe and CIGS taking up much of the remaining market. Modules can be separated by crushing or cutting, or by thermal or solvent-based delamination. Separation and extraction of semiconductor materials can be achieved through manual, mechanical, wet or dry chemical means, or a combination. Crystalline silicon modules are currently recycled through crushing and mechanical separation, but procedures do exist for extraction and processing of intact wafers or wafer pieces. Use of these processes could lead to the recovery of higher grades of silicon. CdTe panels are mostly recycled using a chemical leaching process, with the metals recovered from the leachate. CIGS can be recycled through oxidative removal of selenium and thermochemical recovery of the metals, or by electrochemical or hydrometallurgical means. A remaining area of concern is recycling of the polymeric encapsulant and backsheet materials. There is a move away from the use of fluorinated backsheet polymers which may allow for improved recycling, but further research is required to identify materials which can be recycled readily whilst also being able to withstand outdoor environments for multi-decadal timespans.

Understanding metal dissolution from solar photovoltaics in MSW leachate under standard waste characterization conditions for informing end-of-life photovoltaic waste management

The upcoming end-of-life solar photovoltaics (PV) waste stream is a huge concern before solid waste professionals due to presence of hazardous metals like lead or cadmium. The objective of present study was to understand the metal dissolution from PVs under four standard waste characterization regulatory tests of U.S., Germany, and Japan and their representativeness with actual landfill leachate. Modules were exposed to real municipal solid waste (MSW) landfill leachate for extended extraction duration, agitation and diluted leachate to investigate the effect of various parameters on metal dissolution. The results indicated that extractions using landfill leachates resulted in lower metal release than standard methods. The leached metal concentrations were found to be within the threshold limits except for cadmium, copper, lead and selenium, with maximum lead release from amorphous-PV of 8.68 mg/L and 6.91 mg/L with respect to TCLP and WET tests, respectively. Arsenic showed negligible release with maximum concentration of 0.046 mg/L from copper indium gallium de-selenide(CIGS) PV. Regardless of small size (1-2 cm pieces) and agitation, Germany and Japan's standard tests resulted in minimal release except of copper from copper indium gallium de-selenide PV. Leaching without agitation, showed negligible release from all photovoltaics whereas when agitation is applied to diluted leachate, significant release was observed with aluminum and copper leached up to 145.32 mg/L (multi-crystalline silicon) and 139.01 mg/L (amorphous-PV), respectively. CIGS was found to be most hazardous with a Metal Hazard Score (calculated on the basis of magnitude of leached metals with respect to their threshold limit and subsequent health effects) of 23.19, when exposed to standard tests. For all scenarios, increased metal release was observed with decrease in sample size and increase in leachate dilution and thus, leaching in highly acidic conditions are by no means representative for modules dumping in realistic conditions.

Environmental impacts of solar energy systems: A review

The annual increases in global energy consumption, along with its environmental issues and concerns, are playing significant roles in the massive sustainable and renewable global transmission of energy. Solar energy systems have been grabbing most attention among all the other renewable energy systems throughout the last decade. However, even renewable energies can have some adverse environmental repercussions; therefore, further attention and proper precautional procedures should be given. This paper discusses in detail the environmental impacts of several commercial and emerging solar energy systems at both small- and utility-scales. The study expands to some of the related advances, as well as some of the essential elements in their systems. The approach follows all the stages, starting with the designs, then throughout their manufacturing, materials, construction or installation phases, and over operation lifetime and decommissioning. Specific solutions for most systems such as waste minimization and recycling are discussed, alongside with some technically and ecologically favorable recommendations for mitigating the impacts.

Ecological and human health risk assessment of metals leached from end-of-life solar photovoltaics

Photovoltaic industry has shown tremendous growth among renewable energy sector. Though, this high installation rate will eventually result in generation of large volume of end-of-life photovoltaic waste with hazardous metals. In present study, reported leached metal contents from different photovoltaics in previous investigations were utilized for (i) potential fate and transport analysis to soil and groundwater and, (ii) estimating ecological and human health risks via dermal and ingestion pathways for child and adult sub-populations. The results indicate that the children are at highest risk, mainly due to lead (hazard quotient from 1.2 to 2.6). Metals, such as cadmium, lead, indium, molybdenum and tellurium pose maximum risks for child and adult sub-populations via soil-dermal pathway followed by soil-ingestion pathway. This is further proved by calculated high values of contamination factor and geo-accumulation index for cadmium (102.4), indium (238.9) and molybdenum (16.12). The estimated soil contamination is significant with respect to aluminium, silver, cadmium, iron, lead, however, groundwater contamination was insignificant. Exposure to polluted soils yields an aggregate hazard index (for non-cancer effects) > 1 for all four pathways, with soil dermal pathway as the major contributor. Lead poses significant cancer risk for all scenarios (average risk: 0.0098 to 0.047 (soil) and 2.1 × 10^-5 to 3.5 × 10^-5 (groundwater)), whereas acceptable non-cancer risk was observed for other metals from groundwater exposure. Further, variance contribution and spearman correlation coefficient analysis show that metal concentration, exposure frequency and ingestion rate are the main contributors towards overall uncertainty in risk estimates. More detailed assessment for environmentally-sensitive metals should be carried out by considering other field breakage scenarios also, although the assessment suggests low risk for majority of metals examined.

Sustainable End of Life Management of Crystalline Silicon and Thin Film Solar Photovoltaic Waste: The Impact of Transportation

This work provides economic and environmental analyses of transportation-related impacts of different photovoltaic (PV) module technologies at their end-of-life (EoL) phase. Our results show that crystalline silicon (c-Si) modules are the most economical PV technology (United States Dollars (USD) 2.3 per 1 m2 PV module (or 0.87 ¢/W) for transporting in the United States for 1000 km). Furthermore, we found that the financial costs of truck transportation for PV modules for 2000 km are only slightly more than for 1000 km. CO2-eq emissions associated with transport are a significant share of the EoL impacts, and those for copper indium gallium selenide (CIGS) PV modules are always higher than for c-Si and CdTe PV. Transportation associated CO2-eq emissions contribute 47%, 28%, and 40% of overall EoL impacts of c-Si, CdTe, and CIGS PV wastes, respectively. Overall, gasoline-fueled trucks have 65–95% more environmental impacts compared to alternative transportation options of the diesel and electric trains and ships. Finally, a hotspot analysis on the entire life cycle CO2-eq emissions of different PV technologies showed that the EoL phase-related emissions are more significant for thin-film PV modules compared to crystalline silicon PV technologies and, so, more environmentally friendly material recovery methods should be developed for thin film PV.

Metal dissolution from end-of-life solar photovoltaics in real landfill leachate versus synthetic solutions: One-year study

To investigate the after end-of-life concerns of solar panels, four commercially available photovoltaics (reduced to 15×15 cm² size) in broken and unbroken conditions were exposed to three synthetic solutions of pH 4, 7, 10 and one real municipal solid waste landfill leachate for one year. Metals leaching, encapsulant degradation and release, probability of leached metals exceeding their surface water limits, and change in pollution index of leachate after dumping of solar panels were investigated. Rainwater simulating solution was found to be predominant for metal release from silicon-based photovoltaics, with silver, lead and chromium being released up to 683.26 mg/L (26.9%), 23.37 mg/L (17.6%), and 14.96 mg/L (13.05%), respectively. Copper indium gallium (de) selenide (CIGS) photovoltaic was found to be least vulnerable in various conditions with negligible release of indium, molybdenum, selenium and gallium with values ranging between 0.2 and 1mg/L (0.30%-0.74%). In contrast, minimal metals were released in real landfill leachate compared to other leaching solutions for all photovoltaics. Positive correlation was observed between encapsulant release and metal dissolution with a maximum encapsulant release in silicon-based photovoltaics in rainwater conditions. The calcualtion of values of probability of exceedance of leached metals to their respective surface water limits for aluminium (multi- and mono- crystalline-silicon), silver (amorphous photovoltaic) and indium (CIGS) indicated maximum value to be 92.31%. The regression analysis indicated that conditions of the modules and pH of the leaching solution play significant roles in the metal leaching. The increase in leachate contamination potential after one-year of photovoltaics dumping was found to be 12.02%, 10.90%, 15.26%, 54.19% for amorphous, CIGS, mono and multi crystalline-silicon photovoltaics, respectively. Overall, the maximum metal release observed in the present study is 30% of the initial amount under the most stressful conditions, which suggests that short-term leaching studies with millimeter sized sample pieces do not represent the realistic dumping scenarios.

Eco-Design of Energy Production Systems: The Problem of Renewable Energy Capacity Recycling

Due to the rapid development of recycling technologies in recent years, more data have appeared in the literature on the environmental impact of the final stages of the life cycle of wind and solar energy. The use of these data in the eco-design of modern power generation systems can help eliminate the mistakes and shortcomings when planning wind and solar power plants and make them more eco-efficient. The aim of this study is to extend current knowledge of the environmental impacts of most common renewables throughout the entire life cycle. It examines recent literature data on life cycle assessments of various technologies for recycling of wind turbines and photovoltaic (PV) panels and develops the recommendations for the eco-design of energy systems based on solar and wind power. The study draws several general conclusions. (i) The contribution of further improvements in PV’s recycling technologies to environmental impacts throughout the entire life cycle is insignificant. Therefore, it is more beneficial to focus further efforts on economic parameters, in particular, on achieving the economic feasibility of recycling small volumes of PV-waste. (ii) For wind power, the issue of transporting bulky components of wind turbines to and from the installation location is critical for improving the eco-design of the entire life cycle.

Potential environmental risk of solar cells: Current knowledge and future challenges

Photovoltaic (PV) technology such as solar cells and devices convert solar energy directly into electricity. Compared to fossil fuels, solar energy is considered a key form of renewable energy in terms of reducing energy-related greenhouse gas emissions and mitigating climate change. To date, the development and improvement of PV technologies has received substantial attention; however, their potential environmental risks remain unknown. Therefore, this review focuses on the potential risks of leachates derived from solar cell devices. We collect scientific literature on toxicity and leaching potential, tabulate the existing data, and discuss related challenges. Insufficient toxicity and environmental risk information currently exists. However, it is known that lead (PbI₂), tin (SnI₂), cadmium, silicon, and copper, which are major ingredients in solar cells, are harmful to the ecosystem and human health if discharged from broken products in landfills or after environmental disasters. Several research directions and policy initiatives for minimizing the environmental risks of PV technology are suggested. This review contributes to both solar energy and environmental science research.

The externalities of energy production in the context of development of clean energy generation

In this paper, we present a comparative review of the externalities of electricity production. First of all, the environmental impact is considered. A discussion of the influence of various electricity production processes on human health follows. The studies are conducted in the context of historical development. Current trends, as well as a historical background that resulted in the changes that can be observed today, are presented. The considerations are supported by a few case studies. Analysis of perspectives for the development of electricity generation methods, in particular the indication of clean energy sources and the perspectives of their exploitation, is the main aim of this paper.

Sustainable technology for mass production of Ag nanoparticles and Al microparticles from damaged solar cell wafers

Solar cell industry produces high quantities of waste in form of broken, damaged, and rejected cells, whereas milling and filtering practices are typically used to recover the valuable materials (Al, Ag and Si) from such Waste Solar Cell Wafers (WSCWs). This recycling approach has its disadvantages, e.g. excessive energy consumption and dust emission causing loss of valuable metals. To fulfil the concept of Zero Waste for WSCWs, the authors present a sustainable technology for liberation of valuable metals from WSCWs and synthesis of added value products, in particular Ag nanoparticles and Al microparticles. The suggested technology consisted of three different approaches combined to liberate each material individually. The technology started with an Al layer disintegration process using Dimethyl Sulfoxide (as an eco-friendly and sustainable solvent) supported by ultrasonic treatment to break van der Waals' bonding between spherical Al microparticles that compose the Al paste layer, thus liberating Al in microparticle suspension form with particle size ∼3 μm, recovery rate >98%. After that, leaching by nitric acid and other eco-friendly reagents (Sodium Chloride, Ammonia solution and glucose syrup) assisted by ultrasonic treatment was used to dissolve Ag and later precipitate it in form of nanoparticles with avg. size 30 nm, yield >92%. Finally, etching using paste containing phosphoric acid was done to remove anti-reflection coating and purify the Si substrate with final recovery rate >99%. SEM-EDS, XRD, FTIR, and TEM were used for analysis of extracted materials as well as changes in the solvent. Investigation was also concerned with determining economic/global warming impacts of the technology.

Innovative device for mechanical treatment of End of Life photovoltaic panels: Technical and environmental analysis

The paper contributes at filling the lack of knowledge on Photovoltaic (PV) panels recycling through the analysis of a mobile mechanical treatment plant developed within the context of a European project. The process, the machinery installed in the system and their main functionalities are described. The data are used to perform a Life Cycle Assessment (LCA) focused on the End-of-Life (EoL) process, assuming as Functional Unit (FU) the treatment of a 20 kg PV panel. The system boundaries include construction and operation of the device as well as recycling and incineration of different material fractions performed outside the plant. The inventory is mainly based on primary data coming from a collection carried out directly on the recycling device. The results show that impacts are concentrated on operation stage mainly due to energy consumption involved in milling and separation activities. The analysis of different operation steps reveals that pre-treatment gives the highest contribution, followed by glass and silicon separation with the lowest quota attributable to copper and polymeric fraction separation. Considering also recycling and incineration processes of EoL waste, the environmental credits due to the avoided production of virgin raw materials counterbalance the burdens of construction and operation for most of impact categories. The comparison of results with existing LCAs of fixed recycling installations stresses that the use of a mobile system involves considerable environmental benefits thanks to the reduction of transports needed to move EoL PV waste to the recycling facility site.

Energy efficient production of glass-ceramics using photovoltaic (P/V) glass and lignite fly ash

This study investigates an innovative approach for the valorization of specific wastes generated from the energy sector and the production of glass-ceramics. The wastes used were photovoltaic (P/V) glass, produced from the renewable energy sector, and lignite fly ash, produced from the conventional energy sector. The process first involved the production of glass after melting specific mixtures of wastes, namely (i) 70% P/V glass and 30% lignite fly ash, and (ii) 80% P/V glass and 20% lignite fly ash, at 1200 °C for 1 h as revealed by the use of a heating microscope. The results indicated that the P/V glass, as a sodium-potassium-rich inorganic waste, reduces energy requirements of the melting process. The produced glass was then used for the production of glass-ceramics. Dense and homogeneous glass-ceramics, exhibiting high chemical stability and no toxicity, were produced after controlled thermal treatment of glass at 800 °C. The mechanical (compressive strength, Vickers hardness) and physical (open porosity, bulk density and water absorption) properties of the produced glass-ceramics were evaluated. X-ray diffraction (XRD) and Energy Dispersive X-ray fluorescence (ED-XRF) were used for the characterization of the raw materials and the produced glass-ceramics. Scanning electron microscopy (SEM) provided further insights on the microstructure of the final products. The properties of the produced glass-ceramics, namely water absorption and compressive strength, render them suitable for applications in the construction industry. The waste valorization approach followed in this study is in line with the principles of circular economy.

Evaluation and comparison of pre-treatment techniques for recovering indium from discarded liquid crystal displays

Over the last years, emerging incentives for secondary production of high tech-metals, found in e-waste, are created because of their increasing demand and economic issues associated with their primary production. Due to the very low share of these metals in e-waste, pre-treatment methods can result in an output fraction rich in the metals of interest and may, therefore, be essential. To this scope, the present article evaluates and compares the efficiency of four different pre-treatment approaches containing various steps for recovering indium (In) from liquid crystal displays (LCDs) in laptop computers. The pre-treatment steps, used in various combinations, are (a) dry mechanical crushing and sieving, (b) pyrolysis, (c) thermal shock and (d) gravimetric process. Also, in all approaches, liquid crystals were removed from the samples, before applying the mechanical crushing step, as these are toxic and potentially harmful to human health and the environment. The removal was achieved by ultrasonic irradiation or mild agitation and optimized in terms of time, temperature and solvent type and concentration. Then, the feasibility of each pre-treatment approach was evaluated based on two parameters: (a) the content of In in the resulting sample after pre-treatment and (b) the separated mass share (%) with larger indium content as compared to the original LCD panel. The results showed that In is highly liberated in the fractions consisting of finest particles (<25 μm and <53 μm) after dry mechanical crushing and sieving with a maximum content of 234 mg/kg, which is twice as much as in the raw material. However, these particles represented only about 14 wt% of the original LCD panel mass. On the contrary, thermal shock results indicated that this was the most efficient pre-treatment approach, as both the content of In and the separated LCD mass (%) remained in high levels. Finally, some economic aspects associated with the processes are presented.

Preparation of Si-SiOx nanoparticles from volatile residue produced by refining of silicon

Residual Si was produced on a furnace wall when upgraded metallurgical grade Si was refined by electron beam melting. It was then recycled to prepare Si-SiO_x nanoparticles with an average size of 100 nm by planetary ball milling. The obtained Si-SiO_x nanoparticles mainly consist of amorphous Si, crystalline Si and amorphous SiO_x, which was confirmed by XRD, FTIR, XPS and TEM. SiO_x is mainly composed of SiO₂ and SiO_1.35. Distilled water used as a grinding aid not only enhances milling efficiency, but also plays a key role in obtaining SiO_x. During refining of upgraded metallurgical grade Si, the deposition pattern of residual Si on furnace wall agrees with model of three-dimension growth. Growth of Si-SiO_x nanoparticles is the mutual effect of distilled water and ball milling. Si-SiO_x nanoparticles were doped into phenolic resin pyrolysis carbon as anode materials for lithium ion batteries, and 10% doping was observed to improve the specific capacity. After 500 cycles, specific capacity of delithiation remained around 550 mA h/g. It suggests the residual Si is a value-added by-product, and it can be recycled as anode materials for lithium ion batteries.