Silicon does not exist in pure form in nature. What exists is silica, ordinary sand, abundant and cheap. To produce metallurgical-grade silicon, silica is reduced in an electric arc furnace at around 2,000 °C. To reach the purity required for photovoltaic cells, a further refining stage follows in a Siemens reactor at 1,100 °C. The silicon inside a solar panel is not valuable because the raw material is scarce. It is valuable because of the energy and industrial process locked inside it, energy that took extreme temperatures, controlled atmospheres and highly specialised equipment to deliver. That context matters enormously when evaluating what recycling can and cannot achieve.
No PV recycling process, mechanical, thermal at low or high temperature, chemical, or any combination produces silicon pure enough to be used in new solar panels. This is not a technology gap waiting to be closed by the next generation of equipment. It is a physical constraint. The purity of solar-grade silicon was built in a furnace at 2,000 °C and a reactor at 1,100 °C. It cannot be reconstructed by softening an encapsulant, peeling a laminate, or granulating a panel at end of life. The same applies to glass: float glass for new PV modules is produced in dedicated furnaces from high-purity raw materials — not by re-melting glass recovered from used panels. Any company claiming to deliver solar-grade silicon or panel-quality glass directly from a recycling line is selling a narrative, not an industrial result.
What comes out of an industrial solar panel recycling process, including Stokkermill's, is a silicon concentrate: crystalline silicon accompanied by silver from the bus bars, residual glass, and traces of other metals. It is not a raw material ready for a new panel. It is a concentrated fraction with real and measurable value, which enters specialised hydrometallurgical or metallurgical recovery chains downstream. The economic driver of that concentrate, today, is silver. XRF analysis on samples processed through our lines consistently measures silver concentrations of 2,500 to 4,800 ppm. At those concentrations, silver recovery through hydrometallurgical processing delivers the primary return on the material. Secondary value comes from tin, copper and other metals present in smaller quantities. The silicon matrix itself, in the current market, is a carrier for those metals, not the end product.
For operators building or evaluating a PV recycling line, the economic model needs to be built around what the process actually produces, not around aspirational material destinations. The aluminium frame is clean, directly saleable scrap and generates immediate revenue at every tonne processed. The copper from junction boxes and wiring is straightforward to recover and sell. The glass fraction has a market as cullet in the construction sector, at moderate value. The silicon concentrate, the fraction that attracts the most commercial storytelling in the industry, has its real value in the silver it carries. Processing that concentrate through a downstream hydrometallurgical partner to recover silver, plus tin and copper, is where the meaningful return on the non-ferrous fraction lies. Any business case for a PV recycling investment that assigns high value to recovered silicon as a panel raw material should be treated with scepticism.
The question the industry needs to answer honestly is where silicon concentrate from PV recycling realistically goes, and at what value. Today, the most commercially viable routes are hydrometallurgical recovery, where silver, tin and copper are extracted through leaching and electrochemical processes and metallurgical recovery, where the silicon concentrate is used as an input in alloy production or other industrial processes at metallurgical grade, well below solar purity. Research into upgrading recovered silicon through remelting and refining is active, but the energy cost of rebuilding solar-grade purity from a contaminated concentrate is, at current technology and energy prices, not economically competitive with producing virgin solar-grade silicon from silica. The realistic near-term destination is the hydrometallurgical chain, optimised for silver. That is where the value is. That is what an honest recycling line delivers. At Stokkermill, we prefer to have the harder conversation now, because operators who build their business model on accurate numbers outperform those who build it on marketing claims.
