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Around the world, smelters use massive amounts of electricity — often generated by fossil fuels — to turn raw materials into aluminum. As more carbon-free energy comes onto the grid, these power-hungry facilities will get progressively cleaner. But smelters will never be entirely emissions-free until producers can solve a much trickier technical problem.
That’s because modern aluminum plants rely on a 19th-century process that uses big blocks of carbon, which account for almost one-sixth of the greenhouse gases associated with producing new aluminum globally. Replacing the blocks is crucial to decarbonizing this key industrial process.
Now the industry may be one step closer to reaching that goal.
Earlier this month, the Canadian firm Elysis said it hit a major milestone when it deployed an industrial-size, carbon-free anode inside an existing smelter in Alma, Quebec. Elysis is a joint venture of the U.S. aluminum giant Alcoa and global mining company Rio Tinto, both of which produce aluminum in the Canadian province.
“This is really a first for the aluminum industry, and a worldwide first as well,” François Perras, president and CEO of Elysis, told Canary Media.
Elysis installed its “inert,” or chemically inactive, anode technology in a 450-kiloampere (kA) cell, the same amount of electric current used in many large, modern smelters. The full-scale prototype is a significant step up from the company’s 100 kA pilot unit, which has produced low-carbon aluminum used in certain Apple laptops and iPhones, Michelob Ultra beer cans, and the wheels for Audi’s electric sports car.
Elysis launched in 2018 and has raised over 650 million Canadian dollars ($460 million) in investment for the effort, including from the governments of Canada and Quebec. The 450 kA cell will undergo several more years of testing as the company works to measure and validate how the larger unit performs inside a commercial smelter.
Rio Tinto, meanwhile, has already licensed the inert-anode technology from Elysis. The manufacturer plans to build a demonstration plant with 10 of the 100 kA cells at its existing Arvida smelter in Quebec, possibly by 2027, through a joint venture with the provincial government.
“We’re trying to replace a process that has been used for close to 140 years,” Perras said of the initiatives.
Elysis belongs to a small but persistent group spread across China, Iceland, Norway, and Russia that aims to disrupt the smelting method known as the Hall–Héroult process.
Smelting involves dissolving powdery alumina in a molten salt, which is heated to over 1,700 degrees Fahrenheit. Large carbon anodes are lowered into the highly corrosive bath, and electrical currents run through the entire structure. Aluminum then deposits at the bottom as oxygen combines with carbon in the blocks, creating CO2 as a by-product. It also releases perfluorochemicals (PFCs) — long-lasting greenhouse gases — as well as harmful sulfur dioxide pollution.
The anodes themselves are made using petroleum coke, a rocklike by-product of oil refining.
The Hall–Héroult process was revolutionary, but it is extremely energy-intensive. Most of the emissions associated with producing aluminum are tied to electricity production. In the United States, more than 70% of CO2 pollution from six operating smelters came from the power supply in 2021, according to the Environmental Integrity Project. (The U.S. now has four smelters left, three of which rely on fossil-fuel power.)
Another 20% of U.S. smelters’ carbon emissions were directly from the electrochemical process, the EIP study found. Smelting was also responsible for virtually all the PFCs reported by metal producers to the Environmental Protection Agency that year.
The solution to reducing electricity-related emissions is relatively straightforward: Deploy vast amounts of wind, solar, battery storage, and other clean energy sources. But completely eliminating emissions from the smelting process requires redesigning how the anodes and cells work — and researchers are only just beginning to develop commercial-size alternatives.
Smelting represents “the hardest-to-abate emissions from primary aluminum production,” said Caroline Kim, a technical analyst on climate and energy at the Natural Resources Defense Council. “It’s really important that we’re able to replace carbon anodes,” she added, noting that PFCs last for tens of thousands of years longer in the atmosphere than CO2 does.
Elysis and other inert-anode developers have been tight-lipped about the composition and performance of their technologies, often citing trade secrets. But Elysis’ industrial-scale prototype, as well as Rio Tinto’s future demonstration plant in Quebec, could provide key answers about whether inert anodes can become the game-changing solution that many aluminum and climate experts are betting on.
“Now that it seems like [Elysis’] technology can work, the question is more about, can it be done at full-scale, sustained operating conditions at or below current costs?” Kim said.
Perras didn’t say what kinds of materials Elysis uses in its anodes. “This is our secret sauce,” he explained. But generally, the idea is to use inert metallic alloys or ceramics that don’t contain carbon, and thus won’t release CO2 and PFCs when zapped with electricity.
Elysis has also swapped the horizontal design of typical smelting pots for a “vertical approach” that Perras said looks more like a battery. These and other technical changes are expected to increase the lifespan of anodes by several years, so aluminum producers won’t have to replace them as often as they do carbon blocks, ideally reducing costs.
Aluminum experts have pointed out that the new technology could, in theory, consume more total electricity than conventional anodes, which would raise smelters’ energy needs even higher. But Perras said that Elysis is focused on making its technology competitive on both costs and energy consumption. “What we are targeting, and what we’ve seen so far, is that the technology we have is in a similar bracket of operation ranges from the incumbent Hall–Héroult technology,” he said.
Eventually, aluminum companies will be able to install Elysis’ technology in existing smelters — whenever they decide to expand production or replace old smelting pots — or in new facilities, Perras said.
In the United States, Emirates Global Aluminium is planning a $4 billion smelter in Oklahoma, while Century Aluminum is evaluating sites for a plant in the Ohio and Mississippi River Basins. Given that Elysis is aiming to mature its full-scale technology by the end of this decade, it seems unlikely that the new U.S. facilities will use inert anodes initially.
The news of Elysis’ milestone comes as the Trump administration guts federal funding for industrial decarbonization projects domestically.
Ian Wells, the federal industrial lead on climate and energy at the Natural Resources Defense Council, said the United States should be making similar investments in large-scale innovation projects to remain competitive with other countries.
Still, “we want to see emissions reductions around the world,” Wells said. If Elysis’ technology works as promised, he added, “it could be a real win for climate, and something that could help aluminum production really compete in an increasingly carbon-conscious global economy.”
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