PV Module Recycling Needs Adaptable Infrastructure and High-Purity Silicon Recovery

PVTIME – Exponential increase in solar adoption across the globe has been made possible by the falling cost of solar. As a result of this increase, the volume of modules that will be reaching the end of their service life will be growing at the same rate. With the average lifespan of a solar panel being approximately 25 years, many installations from the early 2000’s are set to reach the end of the cycle soon, making the end-of-life management of PV technologies a key area of focus for the industry.

The International Renewable Energy Agency (IRENA) has estimated that more than 78 million tons of solar PV module waste will be in circulation by 2050. Two options for solar modules that have reached their end-of-life are recycling or landfilling. In terms of cost, sending PV waste off to landfills is undoubtedly cheaper than recycling. However, the presence of heavy metals such as lead and tin in solar modules can result in significant pollution issues for the environment. Furthermore, the presence of valuable metals the likes of silver and copper also curtail the feasibility of sending modules to landfills as such value cannot be retrieved this way. Therefore, recycling should replace landfilling as a means to prevent pollution and retrieve value from solar modules that have reached their end-of-life.

Although recycling cannot be considered as the economically favorable option at this point in time, methods for recycling solar modules are being developed worldwide to better prepare for the inevitable influx of PV waste. The fact of the matter is that the amount of PV waste will only increase given how rapidly the PV industry has expanded in the last decade. In terms of challenges, from a technical standpoint, current recycling methods are mostly based on downcycling processes, recovering only a portion of the materials and value, leaving plenty of room for progress in this area. On the policy front, only Europe has a strong regulatory framework in place to support recycling currently, but other countries are starting to build specific frameworks related to PV waste. Under the Waste Electrical and Electronic Equipment (WEEE) Directive, which was extended to solar products in 2012, the EU requires 85% collection and 80% recycling of the materials used in PV modules. It’s clear that sustainable development of the PV industry should be supported by regulatory frameworks and institutions across the globe, but this is not the case at the moment.  

With a weight composition of 75% glass, 10% polymer, 8% aluminum, 5% silicon, 1% copper, and less than 0.1% silver and other metals, crystalline silicon (c-Si) PV modules currently dominate the market share of PV modules and are mostly recyclable. Materials such as glass, aluminum, and semiconductors can theoretically be recovered and reused, so it is vital that consumers, PV producers, and the industry need to take responsibility for the end-of-life management of these modules. Back in February of this year, PV Cycle, a non-profit EU solar module recycling organization founded in 2007, announced that it had collected 5000 tons of modules in France, of which 94.7% could be recycled. As the first organization to establish a PV recycling process and PV waste logistics throughout the EU, PV Cycle’s process of recycling PV achieved a record recycling rate of 96% for c-Si PV modules (fraction of solid recycled) in 2016, which is a percentage that surpasses the European WEEE standards. The process begins with the removal of the cables, junction box and frame from the PV module. Then, the module is shredded, sorted and separated. The separation of the materials allows them to be sent to specific recycling processes associated with each material.

PV recycling process improvements need to focus on avoiding damages to PV cells, improving economic feasibility, and achieving a high recovery rate of materials that are scarce and valuable. Structurally, silicon wafers account for almost half the cost of a solar module and are the main source of PV waste once the aluminum frames and glass covers are removed from the module during the recycling process. However, the current rates of recovery and reuse of solar grade silicon is low and have significant room for improvement. With current technologies, one main obstacle to the growth of the PV recycling industry is that high temperature thermal processes and mechanical processes can create impurities. Also, low temperature processes that are used with specific mechanical or chemical steps can generate impurities as well. Therefore, the ideal outcome can only be achieved with a combination of thermal, chemical or metallurgical steps. Once silicon can be recovered without impurities, it will have a higher market value. Thus, prioritising ways of bringing the purity of the recovered silicon to solar grade silicon is a key to improving the cost viability of PV recycling.

Going forward, PV recycling needs to develop a flexible recycling infrastructure that is able to adapt and deal with the increase in the variety of modules. Incremental changes in solar modules are already making it difficult to recycle products from the past. Therefore, the recycling infrastructure needs to anticipate further changes. The unprofitability of the current methods does not mean that the recycling of PV modules should be discarded, especially when PV recycling brings positive influences on the environment, and offers the industry new pathways to sustainable development.