In some cases, producing one tonne of aluminum can result in 14 to 16 metric tons of CO2. //

In 2020, the World Bank released an oft-cited analysis called "Minerals for Climate Action: The Mineral Intensity of the Clean Energy Transition.” In this report, the authors identified aluminum as one of the minerals that would need to have its production scale by a large amount for the world to meet its climate goals. “PV was a large contributor,” Lennon said. “[This] made me think about the problem a bit more.”

However, Lennon said that the World Bank report assumed an early International Energy Agency clean energy roadmap, which predicted that only 4 TW of photovoltaics would need to be installed by 2050. This is a small sum compared to what many updated roadmaps are now predicting.

In Lennon’s paper, she and her team used the target of 60 TW, set by the most recent International Technology Roadmap for Photovoltaics (ITRPV). This would mean that the world would need to produce 4.5 TW of additional capacity each year until 2050 to reach net-zero emissions and limit global warming to under 2°C. For context, by the end of 2020, just over 700 GW were installed. //

From this data analysis, the team was able to predict the amount of aluminum the world would need by 2050.

The total came to 486 million metric tons to be used for frames, mountings, and inverter casings. To put this number into context, the world bank had calculated around 100 million metric tons. “Our estimate is a lot larger than the World Bank’s estimates,” Lennon said. “The amount of aluminum we’re going to have to produce is going to have to increase an awful lot from what we have now.”

The problem is not that there’s not enough aluminum in the world—as it is both quite common and fairly easy to extract. Rather, the required extraction and production could lead to a lot of greenhouse gas emissions. Producing one tonne of aluminum from bauxite—a common source of the element—results in between 14 and 16 metric tons of CO2 or equivalent (the paper assumes the process is done in China), Lennon said. “That’s really high,” she said, adding that the smelting process can be quite energy-intensive. “If your electricity is sourced by coal-fired power or fossil fuels in general, the emissions intensity [can be] huge.”