Solar Panel Recycling: The Challenges

Solar panel waste is set to increase by more than 4000 per cent in the next decade. Is the solar panel recycling industry ready to handle these volumes? With demand for new panels increasing exponentially and raw materials scarce, the race is on.

​​Solar panel recycling is becoming a real challenge. Critical to the UK's net zero strategy, solar energy is a lasting and sustainable option for businesses and households, and it is growing fast.

In 2021, the UK added 730MW of new solar capacity, taking overall volume to 14.6GW, a 5.3 per cent increase from 2020, and — in the second quarter of 2022 — solar power contributed 6.4 per cent of the UK's total electricity generation. Within April's Energy Security Strategy, the Department for Business, Energy and Industrial Strategy (BEIS) confirmed that, by 2035, the UK's solar deployment is anticipated to increase five-fold, taking overall volume to 70GW: around 15 per cent of the UK's projected (and increasing) electricity requirements, according to McKinsey.

An emerging issue is what to do about solar panels once they reach the end of their 30-year lifespan. As market growth continues to surge into the future, so will the burgeoning pile of solar waste. According to the International Renewable Energy Agency (IRENA), the UK is predicted to generate 30,000 tonnes of solar waste in the next decade. Plus, a surge in defunct panels is predicted to hit the market in the 2030s, when solar panels from the millennium begin to falter. IRENA predicts global waste from solar panels will be between 1.7 million and eight million tonnes in 2030.

Further, a potential bottleneck in the supply of raw materials looms, with demand for panels set to surpass the availability of virgin components.

Pressure is building for the solar panel recycling industry to increase its capacity in order to handle the rise of defunct panels and support the manufacture of new solar panels. In July, Sam Vanderhoof, a solar industry expert, suggested that — globally — just one in ten photovoltaic (PV) panels is recycled with the rest ending up in landfill, again referring to data from IRENA.

Within the UK, solar panels are formally classified as Electrical and Electronic Equipment (EEE), under a dedicated Category 14. As such, PV panels are covered by the Waste EEE (WEEE) Regulations; their end-of-life is monitored and the development of solid solar panel recycling infrastructure is already underway.

Solar panel producers are obliged to join a Producer Compliance Scheme (PCS), reporting tonnages introduced to the market and obtaining compliance notes to cover the future recycling of those units. They must also mark products to advise users and treatment facilities of material composition and correct disposal.

Concurrently, distributors must collect end-of-life products. They must have a take-back procedure for PV waste or contribute towards a Government-approved take-back scheme.

However, according to Scott Butler, Chief Executive of Material Focus, an NGO funded from WEEE compliance fees, there are some distinctive considerations that will affect the recovery of solar panels: "With PV you would expect there to be an installer/deinstaller relationship for households. Whilst it's a domestic product, it's not something that many people will be able to handle themselves.

"I imagine that the deinstallation has to involve a registered professional for mains electrics… and they might be the key to managing this [waste]. While it can be difficult because they are not geared up to handle waste, it's not that hard to become a waste carrier."

Butler notes that solar panels now approaching end-of-life might prove challenging to recycle due to the variation in manufacturing: "In terms of recycling, I think the challenge with PVs is going to be understanding the chemistry because, particularly at the start, there are lots of different chemical mixes going on. Stuff that's going to start to come out now is quite old, 20 years is quite a long cycle. So maybe there's an information gap that might need to be plugged as to who put what on the market and what it is."

Recycling processes for panels vary according to solar panel composition, the most common of which is silicon-based. Known for their affordability and flexibility, silicon solar panels constituted a 73.3 per cent share of the market in 2020; thin film accounted for 10.4 per cent and panels manufactured from other materials (dye-sensitised, concentrated photovoltaic, organic hybrids) represented the remaining 16.3 per cent (Chowdhury et al, 2020).

When collected, any PV panel is difficult to disassemble. The aluminium frame and the junction box can be removed simply enough; the challenging part is the laminated flat glass sheet, which contains low amounts of ferrous and non-ferrous metals, plastics and semiconductor material. Regarding treatment solutions, the challenge is not a technical one, as pyrolysis, cryogenic separation (freezing), and mechanical shredding exist as separation techniques for the different materials. The biggest challenge is that PV panels do not generate waste that is similar to packaging waste or consumables with a short lifetime. Therefore, the main question is an economic one: who will invest in a treatment line which has no idea when the waste will arrive?

Thin-film panels involve a treatment process, which requires some additional steps to recover the compound metal ‘cadmium telluride’ environmentally soundly. While a less popular choice, thin-film panels have a more efficient material use, housing a thinner semiconductor, saving on cost and carbon during manufacturing. These panels perform better in lower light and at ‘extreme’ angles, useful for vertical surfaces and facades.

To recover the materials, thin film PV panels are shredded to remove lamination, before the solid and liquid shards are separated by a rotating screw. The film is then removed using acid and peroxide, followed by the removal of interlayer materials with vibration, while the remaining glass and metal are separated and recovered.

Despite current recycling initiatives growing steadily, currently only 80 to 95 per cent of the solar panel materials that make it to recycling are recovered. To advance this, waste management company Veolia is leading a project to bring full solar panel recycling on an industrial scale, in an ongoing project funded by EIT RawMaterials. ReProSolar is developing a highly efficient process for recycling end-of-life panels, allowing for all silicon-based PV module components to be recovered.

Using delamination technology to separate the solar cell from the glass plate, physical and chemical processes recover all materials, including pure silver and silicon, without destroying the PV modules.

In partnership with FLAXRES GmbH and ROSI Solar, two technology companies that are developing new methods to reclaim raw materials from PV panels, the project will test feasibility on an industrial scale by the end of the year, with 5,000 tonnes of decommissioned PV modules to be processed annually at a demonstration plant in Germany in 2024.

Commercialising a complete recycling process is key to meeting the current market challenge, bringing a strong supply of recovered PV panel components to meet the surging demand for panels and handling the mounting volumes of solar panel waste.

Considerable economic gains could be made from recovering high-value PV panel components as demand swells. Silver, for example, while accounting for 0.05 per cent of panel weight, makes up 14 per cent of its market value. Other valuable and recoverable metals include aluminium, copper, and tellurium. According to Rystad Energy, while recovered materials from end-of-life PV panels are currently worth $170 million, they are set to be worth more than $2.7 billion in 2030.

In addition to innovations in the world of solar panel recycling, the design of the panels is also being reimagined with reuse in mind. The Netherlands Organisation for Applied Scientific Research (TNO) revealed their newly-developed ‘Design for Recycling’ (D4R) solar panels in December 2021, manufactured towards end-of-life considerations. The panels, with a tested 30-year lifespan, are designed for easy disassembly without damaging components.

The panels, encapsulated with an adhesive foil, hold an integrated trigger mechanism for the separation of the cells and frames. The process is low-energy and involves no toxic elements.

The research is housed by two projects, the first being the DEREC project, which conceptualised and tested the D4R panels on a small scale to ensure their clean dismantling following a simulated service life. The PARSEC project will then scale up the technology to full-size D4R panels for commercial and residential use.

While it is panels manufactured nearly 30 years ago that pose the current challenge to recyclers, D4R panels can simplify panel recycling to drive the industry forward. And, in addition to the new panels, the consortium is researching recycling techniques for current solar panel models, to achieve pure silicon acquisition for reuse.

Cumulatively, these innovations show promise in their focus on commercialisation, although concern remains as to whether the required scale will be met, with both volumes of defunct panels and demand for new ones increasing. However, if commercialisation efforts go well, and if plans to manufacture panels from completely recovered materials can be delivered, the solar panel industry is looking at a robust circular economy.