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.