Comparative assessment of solar photovoltaic panels based on metal-derived hazardous waste, resource depletion, and toxicity potentials

Solar photovoltaic (PV) cells are used to resolve energy security and climate change problems. Although PV panels have long physical lifetimes, they would be eventually replaced by new ones with higher energy efficiency and then changed to waste. Depending on the types of PV cells, waste PV panels have different environmental impact potentials due to different contents of substances. This study assesses and compares hazardous waste, resource depletion, and toxicity potentials from metals in three types of PV modules (i.e., polycrystalline silicon (Si), amorphous Si, and CIGS (copper/indium/gallium/di-selenite) PVs) on per-watt electricity generation basis. Hazardous waste potentials are examined by using metal leachability tests, and resource depletion and toxicity potentials are evaluated by using life cycle impact assessment methods. The polycrystalline Si and CIGS PVs have hazardous waste potentials due to lead (Pb) and cadmium/selenium, respectively, whereas the amorphous Si PV does not. The polycrystalline Si PV has the highest resource depletion potential due primarily to silver; the CIGS PV has the next highest due primarily to selenium; and the amorphous Si PV had the lowest, which is derived primarily from tin and copper. For toxicity potentials, overall the amorphous Si PV had lower potentials, derived primarily from barium/copper/nickel/zinc, than the polycrystalline Si and CIGS PVs of which the toxicity potentials were primarily form copper/lead/nickel/silver and copper/mercury/molybdenum/nickel/silver, respectively. Therefore, waste polycrystalline Si and CIGS PV panels should be recycled and managed with priority, and PV technology development needs to be directed to amorphous Si PV from the material perspective.