Solar Panel Recycling

With the first generation of photovoltaic cells nearing their useful life (typically 25 to 30 years), the volume of solar panel (photovoltaic cell) waste has increased in the last few years. This trend will continue.

Because of the construction of solar panels, a certain amount of processing is required before the panel components can be recycled. With the projected growth of solar technologies, raw material availability could be constrained. So solar panel recycling will be increasingly important.

Solar Panel Technologies

A typical solar panel uses silicon crystals as a semi-conductor which converts light into electricity. The surface of each crystalline photovoltaic module – often a silicon crystal – is crisscrossed by thin strips of metal (silver and others) which move electricity into the panel’s copper wiring. The solar cells are encapsulated in a protective transparent barrier called EVA (ethylene-vinyl acetate) which is inexpensive and has good optical properties. A layer of glass is placed on top and a plastic backsheet – commonly polyethylene terephthalate (PET) – goes on the bottom. These encapsulating layers provide protection for the solar cells from harsh environments. The entire assembly is contained in an aluminum frame. Separation of the solar panel components can be a challenging process – contributing to the difficulties and costs in their recycling.

Of the three types of solar panels commonly found today: monocrystalline is the most efficient; polycrystalline the cheapest; and thin-film panels the most portable.

First-generation solar panels are crystalline silicon (c-Si) panels, which account for approximately 95% of all solar panels produced to date. Because silicon is readily available, c-Si panels are more affordable and highly efficient. The two types of c-Si panels are: monocrystalline, which can reach efficiencies of more than 20%; and polycrystalline, which tends to be below 20% efficient.

A monocrystalline solar panel is made from single crystal solar cells or "wafers.” Monocrystalline wafers are created from a single silicon crystal formed into a cylindrical silicon ingot. A monocrystalline cell’s composition provides more room for the electrons to move – making it more efficient. However, during the manufacturing of monocrystalline panels, the process of solidification of silicon must be controlled very carefully – increasing production costs. So, while monocrystalline solar cells tend to be more efficient than polycrystalline cells, their costs are higher.

Polycrystalline silicon solar panels – also known as "multi-crystalline" or many-crystals – consist of wafers constructed by melting many silicon fragments together into square molds. The resulting wafers are then cut into individual cells. Because the manufacturing process is much simpler, compared to monocrystalline panels, these panels tend to be less expensive.

Thin-film solar cell (TFSC) panels consist of a single or multiple layers of photovoltaic elements on top of a surface comprised of a variety of glass, plastic, or metal. Compared to first-generation c-Si panels, TFSCs require less semiconductor material. TFSCs use strongly light-absorbing materials – such as cadmium telluride, copper indium gallium selenide, amorphous silicon, and gallium arsenide. Because they are less affected by higher temperatures, TFSCs have lower thermal photovoltaic losses than c-Si panels; but they tend to be more expensive. Currently, TFSC panels have a small share of the solar panel market and are primarily used in mobile applications.

Regulatory Environment

When discarded, solar panels are classified as solid waste and fall under existing federal solid and hazardous waste regulations.

Some solar panels may contain enough metals (e.g., lead) to meet the definition of hazardous waste under the Resource Conservation and Recovery Act (RCRA). In such cases, the generator may use their own knowledge or may determine if the solar panels are hazardous waste by performing appropriate testing, such as toxicity characteristic leaching procedure (TCLP).

Solar panels can be recycled using the transfer-based exclusion if the state in which the solar panel waste is generated and recycled has adopted the 2015 or 2018 Definition of Solid Waste Rule. However, the requirements found in Environmental Protection Agency (EPA) Regulation 40 CFR, Section 261.4(a)(24) must be followed.

Solar panels are not a federal universal waste and cannot be managed as such. However, some states, such as California and Hawaii, have added solar panels as state-only universal waste. In part in response to a petition submitted by a broad coalition of industry associations to regulate solar panels as universal waste and to improve management and recycling of solar panels, EPA is drafting streamlined solar panel end-of-life management requirements – likely to be published in the summer of 2025 – by adding hazardous waste solar panels to the universal waste regulations (CFR 40 Part 273). This should improve management of all solar panel waste and encourage recycling.

Services from HETI

HETI’s staff continually reviews new and proposed changes to regulations and standards to make sure we have current knowledge of compliance and environmental health & safety (EHS) issues. We have extensive experience in supporting our clients though a comprehensive range of regulatory and other services. So, whether there is a need for waste management evaluation, permitting, or other regulatory support, HETI’s professionals are ready to help.

To find out more about HETI’s EHS and regulatory support services, please contact us.

Carmelo Blazekovic Senior Geologist/Senior Environmental Scientist

Phone: 978.263.4044

[email protected]

This article is an interpretation of scientific, technological or regulatory information and is offered as a service to our clients and business associates. This material is not intended to be used or construed as HETI’s professional advice, recommendations or legal opinions. ? Hydro-Environmental Technologies, Inc.