Solar Photovoltaic End-of-Life
Silicon Valley Toxics Coalition Stopping the Solar Photovoltaic Waste Stream Before It Starts
Solar photovoltaic (PV) technology is evolving rapidly to address today’s global climate and energy challenges. The industry’s dramatic expansion and its use of new and increasingly complex materials raise serious health and environmental issues, both in product manufacturing and throughout product lifecycles. A major concern is the fate of millions of PV panels currently in use.
The U.S. generates an estimated 2.2 million tons of e-waste annually…
Today’s solar PV sector bears striking similarities to the emerging electronics industry of the 1980s, when supposedly “clean” manufacturing plants polluted Silicon Valley groundwater, causing death and illness in nearby communities. The high-tech industry’s failure to plan for safe end-of-life product disposal has resulted in a global flood of electronic waste (e-waste). The U.S. generates an estimated 2.2 million tons of e-waste annually, and this will continue to grow with the industry’s rapid rate of technological change.i U.S. e-waste is currently shipped to the poorest parts of the world for manual disassembly and recovery of valuable scrap materials. It is anticipated that in 30 years the world’s poorest in cities like Nairobi, Delhi, and Manila (and also in U.S. prisons) may be sorting our solar PV waste.
The solar PV industry is poised to produce clean and renewable energy to meet the challenges posed by climate change. With the solar PV sector still emerging, we have a limited window of opportunity to address both manufacturing and end-of-life issues and create a truly clean and sustainable solar energy sector. Our failure to do so will risk repeating the disastrous environmental legacy of the electronics industry.
To ensure that this new industrial sector is safe and sustainable, Silicon Valley Toxics Coalition (SVTC) is launching the Clean and Just Solar Industry initiative. As a leader in the fight for a clean and safe high-tech industry, SVTC brings more than 25 years of experience to the environmental, health, and safety issues now facing the solar PV sector. Modeled on SVTC’s landmark work in the electronics industry, the project’s goals are to ensure that:
• Solar PV manufacturers implement programs to take back decommissioned solar panels and recycle the panels responsibly.
• Manufacturers address potential end-of-life hazards in the product design and production processes. Requiring manufacturers to take back their own panels will create incentives to design products that can be recycled in a safe and cost-effective manner.
• Solar PV manufacturers work to eliminate the use of materials that are hazardous to human health and to the environment.
• Solar sector jobs are “green jobs” throughout the supply chain,ii and workers are treated in a socially just manner. The minimum acceptable guidelines would be those outlined in the United Nations Universal Declaration of Human Rights.iii
• Workers and communities are not exposed to harmful materials in the manufacturing, use, disposal, and recycling of PV products.
This fact sheet provides an overview of the potential hazards posed by current PV technology and lays out some of the challenges the industry faces in addressing end-of-life disposal and recycling. SVTC is also preparing an in-depth report that examines environmental, health, and safety impacts associated with the solar industry throughout the entire lifecycle of solar products.
Overview of Solar PV Technology
The solar PV industry has long been dominated by cells based on crystalline silicon. However, the high cost of silicon and the drive to increase efficiency have led to the development of new semiconducting materials and technologies.Many of these thin film technologies contain highly toxic and untested materials.
The most successful of these are thin-film technologies, which often use even rarer and more expensive materials, but require only a thin layer of semiconductor. The most common thin-film materials are amorphous silicon (a-Si) and polycrystalline materials that include cadmium telluride (CdTe) and copper indium (gallium) selenide (CIS or CIGS). Many of these thin-film technologies contain highly toxic and untested materials (see below for more details). Very little is known about the potential environmental, health, and safety consequences of their production processes, and we know even less about hazards that could emerge throughout product lifecycles.
In addition, new materials and processes are rapidly emerging, many of them incorporating nanotechnology. Nanotech relies on the distinctive chemical, physical, and electrical properties of materials at the molecular scale. Unfortunately, most existing U.S. environmental laws do not cover these emerging technologies, and very little is known about the risks nanotech products pose in production, use, and end-of-life disposal and recycling.
Solar PV Waste Is Also E-Waste
Monocrystalline solar cell production currently uses many of the same chemical-intensive manufacturing processes found in the microelectronics industry. Therefore, the PV industry will face many of the same hazardous waste issues. E-waste chemicals and materials found in solar PV components include the following:
• Lead is often used in electronic circuits, including solar PV circuits, for wiring, solder-coated copper strips, and some lead-based printing pastes.iv Lead is highly toxic to the central nervous system, endocrine system, cardiovascular system, and kidneys.v Because lead accumulates in landfills, discarded solar PV panels have the potential to pollute drinking water. In one study, solar PV panels using lead solder exceeded by 30 percent the maximum allowable concentrations for lead in the Toxicity Characteristic Leaching Procedure (TCLP)* standards set by the U.S. Environmental Protection Agency (EPA).vi This can be easily resolved by using lead-free solder. Unfortunately, current U.S. regulations do not require lead-free solder in the manufacture of solar panels (or any electronic devices).vii The E.U. has been more proactive, restricting the sale of electronics that use lead-based solders.
• Brominated flame retardant: Polybrominated biphenyls (PBBs) and brominated diphenylethers (PBDEs) are used in circuit boards and solar panel inverters (which convert DC to AC power). PBDEs, which bioaccumulate in fatty tissues, are recognized as toxic and carcinogenic and are described as endocrine disrupters.viii
• Hexavalent chromium (Cr(VI)) is used in many solar panels as a coating to absorb solar radiation. It is also often used in screws and circuit board chassis. Cr(VI) is considered carcinogenic.ix
• Cadmium is a known carcinogenx and is considered “extremely toxic” by the EPAxi and the U.S. Occupational Safety and Health Association (OSHA). Potential health impacts include kidney, liver, bone, and blood damage from ingestion and lung cancer from inhalation.xii The European Economic Community (EEC) has prohibited the sale of most products containing cadmium for health and safety reasons.
End-of-Life Hazards Associated with Specific Solar PV Technologies
• Crystalline Silicon (c-Si): The first commercial solar modules were made of crystalline silicon (c-Si). These modules are still the most widely produced, comprising more than 70 percent of production in 2006.xiii
End-of-life hazardous waste: As outlined above, c-Si PV circuitry and inverters contain hazardous materials such as lead, brominated fire retardants, and hexavalent chromium. Toxics contained in the modules themselves are below levels regulated by the EPA. Recycling options: Used silicon (Si) wafers can be melted into Si ingots and cut into new wafers. A company located in Freiburg, Germany, is one of the few facilities to provide reuse and recycling services for defective c-Si solar panels.xiv
• Amorphous Silicon (a-Si): Amorphous silicon has a structural composition that allows it to be deposited in thin layers on materials such as plastics, glass, and metal. Commercially available since the 1970s, a-Si cells use very little silicon (about 1 percent of the amount used in c-Si) and are inexpensive to manufacture. They are commonly found in low-power consumer devices such as outdoor lights, watches, and calculators. End-of-life hazardous waste: Amorphous silicon PV panels contain no EPA-regulated toxic materials aside from those contained in the circuit boards (as noted above).
Recycling options: Since most a-Si PV panels are currently found in consumer products, they typically enter into household waste streams. Amorphous silicon cells are also being used in combination with other materials to make multijunction panels (see below). The a-Si components of such panels can be recycled through standard glass recovery/recycling processes.
• Cadmium Telluride (CdTe) Thin-Film PV: CdTe thin-film solar PV cells use layers of CdTe and cadmium sulfide (CdS). CdTe is the fastest growing thin-film technology because it is less expensive to manufacture than other solar PV materials. New start-up companies based in Arizona and Florida are already making CdTe thin films. Future applications include the use of CdTe quantum dots, a product of nanotechnology.xv
End-of-life hazardous waste: While the toxicity of cadmium is well known, there is limited information on CdTe toxicology. CdTe is believed to be less toxic than cadmium compounds found in nickel cadmium (NiCd) batteries.xvi However, tests to-date are inconclusive. Early studies of how metals may leach into groundwater show that CdTe modules failed both the TCLP and DEV tests.xvii,xviii,xix,xx More recent studies indicate that CdTe panels marginally pass TCLP standards,xxi,xxii and one manufacturer reports that its panels currently pass TCLP and DEV tests.xxiii.xxiv CdTe quantum dots are known to cause damage to cell biology and cell death.xxv
Recycling options: There are several experimental methods in development that have the potential to address CdTe recycling, but these are limited to pilot projects.xxvi,xxvii One CdTe PV manufacturer offers a take-back policy that allows its customers (which are now primarily utility companies) to return spent modules to their facility for recycling.xxviii The company will pre-fund anticipated module return and recycling costs with an annuity to be issued by a major international insurance company. Recovery of tellurium (Te) through recycling is important to the industry because of low global availability.
• Copper Indium Selenide (CIS) and Copper Indium Gallium Selenide (CIGS) Thin-Film PV: CIS and CIGS thin-film PV modules rely on new semiconductor materials. CIS and CIGS are much less expensive than c-Si because they can be printed onto glass, and, as thin films, use less material. Companies based in California and Massachusetts are using nanotechnology to increase CIGS efficiency,xxix but with the use of nanotechnology comes uncertainty about environmental, health, and safety hazards.xxx,xxx
End-of-life hazardous waste: Selenium is a regulated substance that bioaccumulates in food webs and is considered highly toxic and carcinogenic by the EPA.xxxii CdTe is often used in these modules as a buffer material, which also introduces the CdTe toxicity issues noted above. CIGS has toxicity levels similar to CIS with the addition of gallium, which is associated with low toxicity. CIS and CIGS use CdS (cadmium sulfide) as a buffer layer, so cadmium is also a potential hazard. In an acute toxicity comparison of CdTe, CIS, and CIGS, researchers found CIGS to have the lowest toxicity, and CdTe to have the highest.xxxiii
Recycling options: No recycling processes have been explored beyond the pilot scale,xxxiv although recovery of indium is essential for industry success because of low global availability.
• Multijunction Solar PV: Multijunction solar PV panels combine two or more different semiconductor materials that capture light from different parts of the solar spectrum. Capturing light from this broader spectrum makes multijunction cells more efficient. The maximum efficiency of a solar cell based on a single material is about 30 percent, but multijunction cells are already approaching 40 percent efficiency in laboratory tests with the help of multijunction concentrators. These use relatively inexpensive optics to concentrate sunlight onto a small surface.xxxv Because of their complexity, multijunction cells are expensive to manufacture, limiting current commercial availability to military and communications satellites. Current multijunction PV cells use gallium arsenide (GaAs), combined with thin-film materials such as CdTe or a-Si. Other materials under development for use in multijunction panels include zinc manganese tellurium, indium gallium phosphide/germanium, and indium gallium nitride; very little is known about the toxicology of these materials.
End-of-life hazardous waste: GaAs crystals will release arsine or arsenic if deposited in landfills. Arsenic is highly toxic and carcinogenic.xxxvi The limited toxicological data on GaAs suggest that it could have profound effects on lung, liver, immune, and blood systems.xxxvii There is little toxicological data on gallium, although it is widely used as a marker/tag in MRI tests and is believed to be safe.
Recycling options: There are no pilot scale recycling facilities for multijunction PV. The global rarity of metals such as indium and tellurium will make recycling essential to the success of solar PV based on these platforms.
• Emerging Solar Cell Technologies: Many solar cell technologies now in the research phase are based on organic materials. Many of these new technologies degrade during operation and are therefore very unstable and far from commercial viability. Technologies being developed include dye-sensitive cells and hybrid cells that combine new organic materials with multijunction cell crystals such GaAs. The instability of these new materials raises serious health and safety concerns, particularly regarding their use in combination with toxic semiconductor materials. In addition, emerging PV technologies are making extensive use of new techniques in nanotechnology, such as the deposition and synthesis of nanocrystals, quantum dots, and nanowires.
End-of-Life Issues Facing the Solar PV Industry
Unfortunately, the rapid evolution of the solar PV industry—along with the diverse, innovative, and complex technologies involved—makes it very difficult to assess all end-of-life hazards. SVTC therefore strongly believes that we need to ensure that solar PV components do not enter the waste stream in the first place. The history of the electronics industry clearly illustrates the need to address end-of-life issues early in the design stage of product development. We cannot afford to wait for the inevitable tidal wave of PV waste before we begin to address this problem.
SVTC’s Clean and Just Solar Industry initiative is exploring a variety of approaches to sustainability in the solar industry. In addition to the issues addressed in this fact sheet, we are looking at ways to encourage continuous improvement of product safety and sustainability through the use of innovative methods such as green chemistry and biomimcry. We are also exploring ways to promote sustainable business practices, create sustainable jobs, and provide economic opportunity for individuals and communities across the economic spectrum.
Among the end-of-life issues being addressed by SVTC’s Clean and Just Solar Industry project are the following (a more extensive report that discusses the potential impacts of the solar industry throughout product lifecycles is currently being prepared by SVTC):
• Where will broken, defective, and decommissioned solar PV modules and panels go?
Without effective and safe recycling programs, broken, defective, and decommissioned solar PV equipment will enter the waste stream. It will end up in landfills (where toxic materials can leach into groundwater) or incinerators (where burning can release toxic materials into the air).xxxviii One disposal option is to recycle solar PV panels at existing responsible e-waste recycling facilities* or at facilities that recycle batteries containing lead and cadmium, thereby keeping toxics out of municipal incinerators and landfills.xxxix However, these hazardous waste recovery facilities are often low tech and in need of substantial research and development to improve their environmental footprint. For example, most recycling facilities reclaim metals using smelters, which are known to increase the risk of lung cancer (from cadmium exposure) in nearby communities and the workplace.xl
• How can the solar PV industry ensure environmental health and safety of products at the end of their lifecycles?
The best opportunity for the solar PV industry to ensure environmental health and safety lies in extended producer responsibility, making manufacturers responsible for products’ end-of-life. This would provide an incentive for companies to design products that can be safely and easily recycled into new solar panels. The European Photovoltaic Industry Association (through their PV Cycle initiative) and the German Solar Business Associationxli have endorsed full lifecycle accountability and product take-back for the solar PV sector. The U.S. needs to create policies and practices that encourage companies to adopt pre-funded take-back policies. We also need to encourage further research on recycling, including options for more sustainable solar PV panels and innovative recovery processes.xlii
• How are the toxicity and environmental and health hazards of decommissioned panels determined?
Decommissioned or defective solar panels are currently considered hazardous waste if they do not meet the Environmental Protection Agency’s (EPA) Toxicity Characteristic Leaching Procedure (TCLP) standards. TCLP is intended to ensure that potentially toxic materials do not leach into the groundwater near waste disposal sites. The E.U. relies on the similar German “DEV S4” (Deutsches Einheitsverfahren) test. The TCLP test is required for all new solar panels that enter the U.S. market. California’s Hazardous Waste Control Law (HWCL) and regulations in several other states provide even stricter hazardous waste designations than the federal government.
• What regulatory framework exists for handling the disposal or recycling of obsolete/decommissioned solar PV panels?
The U.S. regulatory framework for solar PV end-of-life is based on the federal Resource Conservation and Recovery Act (RCRA) and state policies like California's HWCL. If PV components are determined to be hazardous waste, RCRA could be used to regulate their handling, recycling, reuse, storage, treatment, and disposal. In the E.U., Article 13 of the directive on Waste of Electrical and Electronic Equipment (WEEE) mentions the possible incorporation of solar PV products, but they are not currently listed.xliii
• Should the sale of PV solar panels containing hazardous materials be restricted?
The E.U.’s RoHS (Restriction of Certain Hazardous Substances) requires that electronics sold on the E.U. market not contain lead, mercury, cadmium, chromium, polybrominated biphenyls (PBBs), or brominated diphenylethers (PBDEs). U.S. policies, however, are much less restrictive. Based on the known toxicity of many PV materials and the unstudied toxicity of many others, SVTC recommends that the U.S. follow the E.U.’s lead in restricting sales of solar panels that contain materials shown to pose a danger to human health or the environment. Also following the E.U.’s example, the U.S. should apply the so-called “precautionary principle,” restricting sales of products containing materials that have not been proven to be safe.
* The TCLP is designed to ensure that toxic materials do not leach into groundwater near waste disposal sites. The procedure involves grinding up the material tested, simulating the conditions in a landfill, and measuring the amount of contaminants that leach out.
The German “DEV S4” (Deutsches Einheitsverfahren) test, similar to the U.S. TCLP, is used by the E.U. to ensure that potentially toxic materials do not leach into the groundwater near waste disposal sites.
* Recyclers that have signed the landmark "Electronic Recycler’s Pledge of True Stewardship.” Those signing the pledge agree to follow the world’s most rigorous environmental and social criteria for the dismantling and recycling of e-waste.
i Environmental Protection Agency, “E-cycling.” http://www.epa.gov/ecycling/ (accessed July 12, 2008).
ii Raquel Pinderhughes, “Green Collar Jobs: An Analysis of the Capacity of Green Businesses to Provide High Quality Jobs for Men and Women with Barriers to Employment,” (report funded by the City of Berkeley Office of Energy and Sustainable Development), 2007.
iii United Nations General Assembly, Universal Declaration of Human Rights, adopted 1948, amended 1966, http://www.unhchr.ch/udhr/lang/eng.pdf.
iv Vasilis Fthenakis and Ron Gonsiorawski, “Lead-Free Solder Technology from ASE Americas,” (workshop report, BNL-67536, Brookhaven National Laboratory, Upton, NY Oct. 19, 1999).
v Environmental Protection Agency, “Lead in Paint, Dust, and Soil,” http://www.epa.gov/lead (accessed June 21, 2008).
vi Hartmut Steinberger, “HSE for CdTe and CIS Thin Film Module Operation,” (IEA expert workshop, Environmental Aspects of PV Power Systems, Report No. 97072, Utrecht University, the Netherlands, May 23, 1997).
vii Stephanie Zangl, “Regulation scenarios for waste PV modules,” (workshop report, Life Cycle Analysis and Recycling of Solar Modules, Brussels, March 19, 2004).
viii Agency for Toxic Substances and Disease Registry, “Toxicological Profile for Polybrominated Diphenyl Ethers and Polybrominated Biphenyls,” http://www.atsdr.cdc.gov/toxprofiles/tp68.html (accessed July 1, 2008).
ix Centers for Disease Control and Prevention, “Chromium,” http://www.cdc.gov/niosh/topics/chromium (accessed June 28, 2008).
x U.S. Department of Health and Human Services, “Toxicological Profile for Cadmium,” (report, Agency for Toxic Substances and Disease Registry, Atlanta, Georgia, 1997).
xi Environmental Protection Agency, “Technical Factsheet on Cadmium.” http://www.epa.gov/safewater/dwh/t-ioc/cadmium.html (accessed June 10, 2008).
xii Occupational Safety and Health Administration, “Safety and Health Topics: Cadmium,” http://www.osha.gov/ SLTC/cadmium (accessed June 10, 2008).
xiii Energy Information Administration, “Solar Photovoltaic,” http://www.eia.doe.gov/cneaf/solar.renewables/page/ solarphotv/solarpv.html (accessed July 13, 2008)
xiv Karsten Wambach, "Recycling of Photovoltaic Modules," (report, Workshop on Life Cycle Analysis and Recycling of Solar Modules—The "Waste" Challenge, Brussels, March 18-19, 2004).
xv Tracie Bukowski and Joseph Simmons, “Quantum Dot Research: Current State and Future Prospects,” Critical reviews in Solid State and Materials Sciences 27(3 2002): 119–42.
xvi Vasilis Fthenakis, “Life Cycle Impact Analysis of Cadmium in CdTe PV Production,” Renewable and Sustainable Energy Reviews 8(2004): 303–34.
xvii Vasilis Fthenakis, Chris Eberspacher, and Paul Moskowitz, “Recycling Strategies to Enhance the Commercial Viability of CIS Photovoltaics,” Progress in Photovoltaics 4 (1996): 447–56.
xviii Paul Moskowitz, Harmut Steinberger, and Werner Thumm, “Health and Environmental Hazards of CdTe PV Production, Use, and Decommissioning,” (report, World Conference on Photovoltaic Conversion, Waikoloa, Hawaii, December 1994).
xix Vasilis Fthenakis and Paul Moskowitz, “Thin-Film Photovoltaic Cells: Health and Environmental Issues in Their Manufacture, Use, and Disposal,” Progress in Photovoltaics 3 (1995): 295–306.
xx Vasilis Fthenakis, “Regulations on PV Module Disposal and Recycling,” (informal report, Brookhaven National Laboratories, Upton, New York, January 29, 2001).
xxi Robert Goozner et al., “A Process to Recycle Thin Film PV Materials,” (26th annual meeting of the Photovoltaic Specialists Society, Anaheim, California, 1997).
xxii Vasilis Fthenakis, “Could CdTe PV Modules Pollute the Environment?” (working paper, National Photovoltaic Environmental Health and Safety Assistance Center, Brookhaven National Laboratory, Upton, New York, 2002).
xxiii Vasilis Fthenakis, "Overview of Potential Hazards," in Practical Handbook of Photovoltaics: Fundamentals and Applications, T. Markvart and L. Castaner (eds.), Elsevier, New York, 2003.
xxiv Erik Alsema, A. Baumann, R. Hill, and M. Patterson, “Health, Safety and Environmental Issues in Thin Film Manufacturing,” (report, Department of Science, Technology, and Society, Utrecht University, the Netherlands, 1996).
xxv Jasmina Lovric, Sung Jo Cho, Francoise Winnik, and Dusica Maysinger, “Unmodified Cadmium Telluride Quantum Dots Induce Reactive Oxygen Species Formation Leading to Multiple Organelle Damage and Cell Death,” Chemical Biology 12(11 2005): 1227–34.
xxvi J.R. Bohland and K. Smigielski, “First Solar's CdTe Module Manufacturing Experience: Environmental, Health, and Safety Results,” (report, Photovoltaic Specialists Conference, 28th annual meeting of the Institute of Electrical and Electronics Engineers, Anchorage, Alaska, 2000).
xxvii Shalini Menezes, “Electrochemical Approach for Removal, Separation, and Retrieval of CdTe and CdS Film from PV Module Waste,” Thin Solid Films 387(1–2 2001): 175–8.
xxviii Peter Meyers, “First Solar Polycrystalline CdTe Thin Film PV,” (report, 4th World Conference on Photovoltaic Energy Conversion, May 2006).
xxix Rommel Noufi and Ken Zweibel, “High-efficiency CdTe and CIGS Thin Film Solar Cells: Highlights and Challenges,” (report, National Renewable Energy Laboratory, Golden, Colorado, 2006).
xxx Silicon Valley Toxics Coalition, “Regulating Emerging Technologies in Silicon Valley and Beyond,” http://www.etoxics.org/site/PageServer?pagename=svtc_nanotech (accessed July 11, 2008).
xxxi Project on Emerging Nanotechnologies, “Where Does the Nano Go? End-of-Life Regulation of Nanotechnology,” (Woodrow Wilson International Center for Scholars, Washington, DC, July 2007).
xxxii Agency for Toxic Substances and Disease Registry, “Toxicological Profile for Selenium,” http://www.atsdr.cdc.gov/ toxprofiles/tp92.html (accessed July 1, 2008).
xxxiii Vasilis Fthenakis, et al., “Toxicity of Cadmium Telluride, Copper Indium Diselenide, and Copper Gallium Diselenide,” Progress in Photovoltaics 7(1999): 489–97.
xxxiv Vasilis Fthenakis, “End-of-Life Management and Recycling of PV Modules,” Energy Policy 28(2000): 1051–8.
xxxv Frank Dimroth and Sarah Kurtz, “High-Efficiency Multijunction Solar Cells,” MRS Bulletin—Materials Research Society 32(3 2007): 230–5.
xxxvi Agency for Toxic Substances and Disease Registry, “ToxFAQs for Arsenic,” http://www.atsdr.cdc.gov/tfacts2.html (accessed June 20, 2008).
xxxvii Swaran Flora and S. Gupta, “Toxicology of Gallium Arsenide: An Appraisal,” Defense Science Journal 44(1 1994): 5–10.
xxxviii Paul Williams, “Dioxins and Furans from the Incineration of Municipal Solid Waste,” Journal of the Energy Institute 78 (1 2005): 38–48.
xxxix Erik Alsema, “Environmental Aspects of Solar Cell Modules,” (report, Netherlands Agency for Energy and the Environment, Utrecht, the Netherlands, August 1996).
xl A. Ades and G. Kazantzis, “Lung Cancer in a Non-Ferrous Smelter: The Role of Cadmium,” British Journal of Industrial Medicine 45(7): 435–42.
xli Janet Wood, “Solar Energy in Germany: A Market Review,” Refocus 7(3): 24–30.
xlii See note 34 above.
xliii Mariska de Wild-Scholten, et al., “Implications of European Environmental Legislation for Photovoltaic Systems,” (report, 20th European Photovoltaic Energy Conference, Barcelona, Spain, June 6–10, 2004).