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I would like to know this in the context of calculating the benefits of solar energy - how the disposal of the materials used impacts the entire life cycle of solar energy generation.
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PV panel waste still falls under the general waste classification in most countries. So they are usually sent to landfill & will produce 60 million tons of PV waste (including toxic substances leaching into the soil) by 2050 if recycling practices are not put in place. A sole exception exists at EU-level, where PV panels are defined as e-waste. However, according to a 2015 United Nations Environment Program (UNEP) report, somewhere between 60 and 90 percent of electronic waste is illegally traded and dumped in poor nations.

 

Solar panels can theoretically be recycled and research has shown it reaching 96% efficiency. The recycling process is shown in detail in the easy to understand infographic by Vekony AT, “The Opportunities of Solar Panel Recycling” (Greenmatch.co.uk, 2019).

Recycling: A Solar Panels Life after Death [infographic]

But in practice:

  • Pollutants such as lead or carcinogenic cadmium can be almost completely washed out of the fragments of solar modules over a period of several months, for example by rainwater. This is even though some solar developers incorrectly claim that the cadmium in the panels is not water soluble.
  • PV module glass often cannot be recycled as float glass due to impurities. Common problematic impurities in glass include plastics, lead, cadmium and antimony.
  • Today recycling costs more than the economic value of the materials recovered, which is why most solar panels end up in landfills.

Processes are still in development. The EU has funded research including the Full Recovery End of Life Photovoltaic (FRELP) project. Italian mining technology firm Sasil, one of the project’s members, has been running a pilot facility based on technology developed by FRELP.

Sasil says it is able to recover 93% of materials from used PV panels. Most of the remaining material is plastic, which is burned in the furnace to provide additional energy.

It is not problem-free: For every 1,000 kg of PV panel waste, about 20 kg of metals, including tin, aluminum, lead, and zinc, are recovered as hydroxides and landfilled. A further 2 kg of material is likely lost as nitrous oxide emissions during electrolysis, and 5 kg of ash results from the reduction of fluorine at the furnace phase.

The quality of the silicon recovered is not high enough for reuse as a photovoltaic material but is suitable to be used in specialty aluminum and steel alloys.

 

Bibliography

Bomgardner MM and Scott A, “Recycling Renewables” (Chemical & Engineering News, 2018)

Shellenberger M, “If Solar Panels Are So Clean, Why Do They Produce So Much Toxic Waste?” Forbes (2018)

Vekony AT, “The Opportunities of Solar Panel Recycling” (Greenmatch.co.uk, 2019)

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