Those concerned about the use of cadmium in CdTe photovoltaic modules generally voice their concerns in the following three areas:
- Manufacturing
- Public/consumer safety
- End-of-life environmental issues.
Those concerned about manufacturing focus on the risk to industrial workers who may breathe contaminated air, the related long-term effects, and the safeguards implemented by the industry. Those with public concerns reference perceived risks to consumers who install CdTe PV modules on or around their homes. Environmentalists have end-of-life concerns, such as landfill leaching and recycling efforts undertaken by the PV industry.
What Are the Benefits of Cadmium Use in Photovoltaics?
1. Using small amounts of cadmium in CdTe thin-film modules will allow the mass production of PV for the commercial marketplace—resulting in reduced levels of atmospheric emissions such as acid rain, particulates, noxious fumes, carbon dioxide, and small amounts of heavy metals.
Utility coal plants produce heavy-metal airborne pollution. When PV replaces burning coal for electricity generation, it will prevent a minimum of 2 g of cadmium in gaseous emissions and about 140 g of cadmium in ash form for each GWh of electricity produced.
During its projected 30 years of clean energy production, a 2-kW rooftop photovoltaic system meeting half of a household's electricity use would generate 100 MWhr of electricity. This allows electrical plants to avoid emissions from burning fossil fuels of more than half a ton of sulfur dioxide, one-third a ton of nitrogen oxides, and 100 tons of carbon dioxide. Now, imagine the environmental benefits resulting from many households and businesses generating their electricity using PV systems. The use of PV technology that removes cadmium from the environment and encapsulates small, inert amounts in sealed modules can achieve significant environmental benefits (Fthenakis 2002).
2. Using cadmium in PV modules effectively sequesters it for the lifetime of the module (20-30 years) and prevents it from ending up on the slag heap or in a landfill.
In the United States Geological Survey (USGS) 2001 Minerals Yearbook, Jozef Plachy writes that because most cadmium is produced as a byproduct of zinc production, any restrictions placed on the use of cadmium in, for example, NiCd batteries could actually increase the amount of cadmium in landfills. He concludes that an effective collection and recycling system for spent batteries would protect the environment. Sequestering cadmium in PV modules would keep cadmium out of the landfills for decades, and at the end of the module's useful life, the cadmium could easily be recycled.
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