Life Cycle Assessment of Photovoltaic Module Production in Mexico: Hidden Impacts of Global Manufacturing

The environmental and human health impacts of mono-crystalline silicon (mono-Si) module assembly in Mexico were estimated using a regionalized Life Cycle Assessment (LCA). A detailed inventory was completed through fieldwork consisting of arranged visits to four manufacturers to collect on-site data. The main findings demonstrate that, on average, between 10% and 35% of the photovoltaic cells imported from China for module assembly in Mexico are discarded during the manufacturing process. Furthermore, experimental studies conducted in our laboratories with samples collected from the manufacturing plants showed that the busbars and finger contacts on the cells and strings indicate the presence of lead and a lack of silver in the aluminum-based alloys used for soldering and coating the strings. The LCA study includes end-of-life scenarios, with particular attention to open-dump waste disposal, the most common option in Mexico, which generates three-times-greater environmental impacts than waste incineration. The impact of different transport options for importing cells from China yielded Global Warming Potential (GWP) values of 157.52 kg CO2 eq and a Cumulative Energy Demand (CED) of 2204.9 MJ eq, compared to 8.9 kg CO2 eq and 123.3 MJ eq, respectively, obtained for sea transport. These results highlight the importance of including transport and end-of-life scenarios to obtain realistic environmental and human health impacts from photovoltaic module manufacturing.