Those concerned about the environmental aspects of cadmium focus on how to safely dispose of and/or recycle the cadmium in thin-film PV modules. Members of the thin-film PV manufacturing industry are currently examining the best way to collaborate in the recycling process. Updates will be posted on this page.
Disposal
First, because solar cells are expected to last 25 to 30 years, the issue of disposal is minimized. Second, today's CdTe PV modules pass federal (TCLP-RCRA) leaching criteria for non-hazardous waste (Fthenakis 2002), unlike fluorescent lights containing mercury and computer screens containing lead, which do not pass landfill-leaching criteria. Landfill leaching is a small concern because PV materials are largely encased in glass or plastic, and many are insoluble.
Recycling and Sequestering
Multiple environmental, safety & health (ES&H) studies have shown that CdTe PV modules do not present any risks to health and the environment and that recycling the modules at the end of their life for their valuable, high-purity cadmium and tellurium completely resolves any environmental concerns. CdTe thin-film modules provide a solution to the challenge of what to do with the cadmium generated from zinc refining and bag-house dust in coal-burning plants and smelters.
Case Study
Because of low cadmium prices and U.S. battery manufacturers moving their operations to China and Mexico, the Big River Zinc Corporation in Sauget, Illinois, ceased production of cadmium in 2000. The company chose to dispose of its cadmium output, rather than refine it (Plachy 2002). Cadmium from sources such as this one could be used in thin-film modules, in which the cadmium would be sealed for 30 years and then recycled.
Cadmium suppliers are willing to take back cadmium wastes for re-smelting and recovery. Two U.S. Department of Energy Small Business Innovation Research grants to Solar Cells, Inc. (now First Solar) and Drinkard Metalox have allowed technology to be developed for recycling wastes from the PV manufacturing process and "spent" CdTe modules (Zweibel, Moskowitz and Fthenakis 1998).
The present recycling systems for batteries and electronics provide useful models for future endeavors (batteries containing cadmium are 100% recyclable, and the recycling costs of approximately 5 cents per Watt are viable). This topic is currently being examined by the industry.
Future work on ES&H issues in the area of CdTe thin-film module disposal and recycling is likely to focus on the following issues:
- The need for industry collaboration in recycling
- Technical issues related to recycling, including methods of removing cadmium from CdTe and CIS module substrates and refining it for reuse
- The economic incentive to design modules that can be recycled at a reasonable cost
- Economical infrastructures for gathering modules at the end of their useful life.
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