With the expansion of renewable energy, solar power has established itself as the leading source of clean energy: in 2010, cumulative capacity stood at around 41.6 gigawatts (GW), while by 2021 it had reached approximately 873.9 GW, representing a growth of more than 2,000 per cent in a single decade. In Italy, installed capacity rose from 3,470 MW in 2010 to 22,560 MW in 2021, recording a growth of 550 per cent.

Although solar energy has a very low environmental impact during its production phase, the life cycle of photovoltaic panels raises a crucial question: how can they be properly disposed of when they reach the end of their life? And then, how can they be recycled? As the uptake of solar installations continues to grow, managing the recycling process is becoming a global challenge.

What types of photovoltaic panels exist

Before answering that question, it is useful to take stock of the broader picture. In 2021, Italy generated 25,039 gigawatt-hours (GWh) of electricity from photovoltaic installations. Puglia remains the region with the highest output, at 3,881 GWh, accounting for 15.5 per cent of the national total. It is followed by Lombardia with 10.2 per cent, Emilia Romagna with 9.6 per cent and Veneto with 9 per cent.

There are several types of photovoltaic panels, each with characteristics that determine their efficiency and cost. The most common are mono- and polycrystalline silicon panels, a technology that is generally more efficient than other types — namely thin-film panels, amorphous silicon panels and cadmium telluride panels. Although the cost of a mono- or polycrystalline silicon panel is higher than the alternatives mentioned, the output in terms of installed power is better, especially under high-temperature conditions and in environments with variable solar irradiance quality.

In 2021, 94.5 per cent of the photovoltaic capacity installed in Italy consisted of monocrystalline and polycrystalline silicon panels. Specifically, 69.8 per cent of Italian panels were made from polycrystalline silicon, 24.7 per cent from monocrystalline silicon, and only 5.5 per cent from thin film or other materials.

How photovoltaic panels are disposed of

According to a study by the International Renewable Energy Agency, Irena, it is estimated that by 2050 around 2.1 million tonnes of photovoltaic panels will need to be disposed of. So, even though manufacturers guarantee a lifespan of between 20 and 25 years for photovoltaic panels, the issue of disposal is already a pressing one, with the earliest installations showing signs of obsolescence after just 12 to 15 years. Maintaining an expanding solar portfolio requires a continuous commitment, and revamping — that is, technological upgrading of installations — is becoming an increasingly attractive option.

In Italy, end-of-life photovoltaic panels are classified as electronic waste (WEEE) and must be disposed of in accordance with European regulations. If the installation is a domestic one (below 10 kW), the panels must be taken to authorised collection centres free of charge, while for higher-capacity installations it is necessary to use specialist operators.

Furthermore, the Conto Energia incentive scheme includes a guarantee on the proper disposal of photovoltaic panels, with a sum withheld by the Gse (Gestore Servizi Energetici) to cover recovery and disposal costs; this sum is returned if the disposal process complies with the relevant regulations.

How they are recycled

That covers disposal. But what about recycling? Photovoltaic panels are composed primarily of materials that are almost entirely recyclable, namely:

• Glass, 70 per cent;
• Plastic (ethylene vinyl acetate + polyethylene terephthalate), 16 per cent;
• Aluminium, 10 per cent;
• Silicon cells, 3 per cent;
• Copper electrical connections, 1 per cent.

There are various recycling processes involving different stages, which can also be carried out in combination with one another. The main recovery techniques include:

• Mechanical treatments, which involve the manual removal of aluminium frames, cables and junction boxes, followed by shredding and screening of the materials;
• Thermal treatments, carried out at high temperatures (450–500°C), which make it possible to separate the solar cells from the glass by destroying the plastic encapsulant;
• Chemical treatments, using acid etching to separate the metal fractions and recover silicon through chemical processes.

A concrete example of a company that has achieved significant results is Sogliano Ambiente Spa: at its facilities in Sogliano al Rubicone, in the province of Forlì-Cesena, the company has developed a mechanical process that makes it possible to recover more than 90–95 per cent of the incoming weight of photovoltaic panels.

In this process, the separation of glass and metals becomes a crucial step in ensuring effective recycling. In particular, the glass processed through Sogliano Ambiente's recovery system has been recognised as "end of waste": this means that, once treated, the glass can be reused as a secondary raw material for the production of new products, such as ceramics and glazes (not for new panels, at least for now).

To conclude, it is worth noting that over its lifetime a solar panel generates far more energy than is needed to manufacture it: its carbon footprint is extremely low, with an average emission of 53 grams of CO2 per kWh produced. This means that investing in research to improve recycling processes will not only help reduce the environmental impact of photovoltaic panels, but will also contribute to making solar energy one of the most effective solutions for a truly sustainable future.