Silicon

Silicon is the second most common element on Earth, constituting approximately 25% of the Earth’s crust, and primarily occurs as silica or silicates.

Silicon recycling feedstock

Common applications of silicon include manufacturing solar panels from polysilicon, producing semiconductors or integrated circuits on chips made from pure silicon, and as silica sand and silicates in the construction industry. However, despite the many potential sources of scrap silicon metal, currently, silicon recycling is relatively insignificant. Recent advancements in technology could affect the amount of critical minerals found in solar PV waste in different ways. Although solar panels are designed to last for many years, improvements in the efficiency of newer solar cells might prompt the early replacement of existing systems, potentially increasing the supply of silicon available for recycling.

Silicon can technically be recycled from both pre- and post-consumer sources, but currently active use of both feedstocks for recycling processes is minimal.

Pre-consumer feedstocks primarily stem from manufacturing processes. A significant contributor is kerf loss during the wafer slicing of silicon ingots, especially in photovoltaic (PV) and semiconductor production. This process can result in up to 40% of the silicon being lost as fine particles, known as kerf, which are often landfilled or used in construction materials. However, advancements are being made to recycle kerf into high-purity silicon suitable for reuse in PV applications.

Post-consumer silicon recycling feedstock includes materials discarded after their initial use. A notable example is end-of-life solar panels, which, after approximately 25–30 years of service, become a valuable source of silicon. These panels contain silicon that can be extracted and purified for reuse in various applications, including the production of lithium-ion batteries.

Photovoltaic (PV) modules that are beyond repair or refurbishment are considered to have reached their end of life (EOL) and are often suitable for recycling. Research highlights that economically viable recycling depends on the recovery of high-purity, high-value materials such as silicon and silver. In recent years, several commercial and demonstration-scale recycling initiatives have been introduced, with some reporting the ability to recover both silicon and silver. However, publicly available information on the processes used in these pilot or commercial facilities remains limited.

Solar PV waste is expected to grow rapidly beginning around 2030, as the earliest installed systems begin to reach the end of their operational lifespan. The International Energy Agency estimates that end-of-life solar panels will generate approximately 13 million tonnes of waste by 2050. While most of this waste will consist of materials like concrete, steel, aluminum, and glass, it will also contain significant quantities of copper, silver, silicon, and other valuable materials that could be targeted for recycling.

Additionally, electronic waste constitutes an important source of post-consumer silicon feedstock. Devices such as smartphones, computers, and other electronics contain silicon components that can be reclaimed and repurposed. While the amount of silicon in these devices is relatively small, the sheer volume of electronic waste makes it a significant source.