Why Chinese Aluminum Producers Emit So Much of Some of the World’s Most Damaging Greenhouse Gases

More than half of the aluminum in the world is produced in China, but it is responsible for 81 percent of the industry’s emissions of PFCs. Simple automation could go a long way toward cutting them.

Grid; Xinhua News Agency/Getty Images

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This article was published in partnership with Grid.

Historically, the global aluminum industry curbed emissions of one of the most potent greenhouse gases using a surprisingly simple method: a stick. Standing over a huge bubbling pot of molten aluminum, workers would plunge a long wooden pole into the pot to stop a chemical reaction that disrupted aluminum production and released the powerful emissions. 

Stephen Andersen, director of research at the Institute for Governance and Sustainable Development (IGSD), an environmental organization based in Washington, D.C, recalled his reaction when he first saw the process at a U.S. smelter in the early 2000s. 

“It didn’t look like a sophisticated company managing a chemical process,” Andersen said. “It was almost like witchcraft.”

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Perhaps unsurprisingly, the stick method wasn’t the most effective. By the 1990s, Western companies were using an automatic system to stop the “anode effect”—the chemical reaction responsible for the emissions. But long after most aluminum producers had left the “stick” behind and automated their operations, one critical country was lagging: China, where more than half of  the world’s aluminum is now produced. 

An investigation by Inside Climate News and Grid found that even as China has made bold new commitments to address climate change, the country’s aluminum giants continue to use the antiquated stick method, allowing the potent emissions to slip into the atmosphere. 

This decision—to stick with the stick, as it were—may seem like a technical detail for plant engineers, but it has significant consequences for the world. That’s because the emissions in question, called perfluorocarbons or PFCs, are some of the planet’s most damaging greenhouse gases. They are part of a group of gases known as “the immortals”—as in, once they go up into the atmosphere, they remain there, heating the planet for tens of thousands of years.

Sizing Up China’s ‘Immortal’ Emissions Problem

China’s aluminum industry is one of the world’s great climate polluters. A 2021 report by Ember, an energy think tank based in London, concluded that the collective emissions from aluminum production in China, including power production, exceeded all the 2020 greenhouse gas emissions from Indonesia, the world’s 8th largest emitter

And while PFC emissions are a small fraction of all greenhouse gas emissions tied to aluminum production, the potency and longevity of PFCs make them particularly concerning. According to the UN’s Intergovernmental Panel on Climate Change, tetrafluoromethane (CF4), the primary PFC released in aluminum production, is 7,380 times worse for climate change than carbon dioxide on a pound-for-pound basis. And unlike CO2, which remains in the atmosphere for approximately 300-1,000 years, CF4 remains in the atmosphere, warming the planet, for 50,000 years.

Why They're Called 'The Immortals'

Each year, aluminum producers in China collectively release approximately 6,000 tons of CF4 and hexafluoroethane (C2F6), another of the world’s most potent and long-lasting greenhouse gases, according to a 2021 study published in the Journal of Geophysical Research: Atmospheres. The pollutants, collectively known as PFCs, have a climate impact equal to the annual greenhouse gas emissions of 10.2 million automobiles, according to the U.S. Environmental Protection Agency.

China plays a disproportionate role in releasing these particular “immortal” gases. The country is responsible for 81 percent of the industry’s PFC emissions, despite producing only 55 percent of global aluminum, according to official estimates reported in the 2021 study. Actual PFC emissions from China’s aluminum industry may be even higher, based on atmospheric measurements of PFC pollution reported in the study.

Anode effects account for nearly one third of PFC emissions at Chinese plants, according to a 2015 study published in the Journal of The Minerals, Metals & Materials Society.  Reducing the occurrence of these chemical reactions is critical.  

More Profits, Fewer Emissions: ‘This Is so Obvious’

More than a decade ago, in 2009, a team of international experts traveled to China to demonstrate an automated control system that could end dependence on the stick method, and dramatically reduce PFC emissions. The experts were working as part of the Asia-Pacific Partnership on Clean Development and Climate, a voluntary program funded in part by the U.S. government.

When a chemical imbalance occurs in a pot of molten aluminum, electricity running through the pot to help break aluminum oxide down into aluminum has to be disrupted to reset the process. Historically, this was the moment when a worker would rush to the pot and stir the molten aluminum with a stick until the liquid metal splashed upward, making contact with the anode at the top of the pot, causing the smelter to short circuit. 

A worker using a wooden pole to manually disrupt the "anode effect" in an aluminum pot at a Reynolds aluminum smelter in Baie-Comeau, Quebec Canada in 1992. Credit: Alton Tabereaux
A worker using a wooden pole to manually disrupt the “anode effect” in an aluminum pot at a Reynolds aluminum smelter in Baie-Comeau, Quebec Canada in 1992. Credit: Alton Tabereaux

The automated control method, developed in the 1970s by U.S. manufacturer Reynolds Aluminum, simply lowered the anode further down into the pot until it made contact with the molten aluminum, achieving the same short-circuiting effect. No stick, and no human being to wield it, required. And it had a significant effect on the “anode effect.”

“In the old days, [the anode effect] could last anywhere from one to three minutes,” said Alton Tabereaux, who worked as a research and technology development manager for Reynolds Aluminum and Alcoa from the 1970s to the early 2000s. “Once we saw that duration was producing a lot of PFCs, then we designed the anode moving down [sic] very quickly, and we could actually terminate the anode effect in 30 seconds. And some plants were even faster than that. It made a tremendous decrease in PFC emissions.”

Tabereaux helped develop the automated method nearly half a century ago and was part of the team of researchers that traveled to China to demonstrate the technology in 2009.

Demonstrations at the Henan Zhongfu Industrial Company, a large Chinese aluminum producer, showed that the automated process cut the average anode effect duration by 53 percent, from 28 seconds to just 13 seconds, according to a 2011 study published in the journal Light Metals.

In addition to reducing emissions, the new technology also yielded a slight increase in plant efficiency, according to the study. 

The researchers assumed that the clear success of their demonstration would lead to widespread adoption in aluminum smelters across China. After all, it wasn’t just good for the planet; it might also boost profits. 

“From our study, it looked like they could actually make more money by being slightly more efficient,” said Durwood Zaelke, president of IGSD, whose organization coordinated the project. “We thought, ‘this is so obvious that it’ll sweep the 100 smelters in China’ at the time.”

It didn’t happen. 

Why China Stuck With the Stick 

Thirteen years after the initial demonstration, Chinese smelters largely continue to rely on manual controls to kill anode effects, industry experts in China told Grid and Inside Climate News.

A survey of Chinese smelters in 2016 by Chinese industry experts found the vast majority continued to use the manual method. The group polled the operators of seven smelters, representing 10 percent of Chinese production, and found that six out of seven relied exclusively on manual methods to cut off anode effects. 

More recently, researchers with Henan Zhongfu Industrial Company, the aluminum smelter that hosted the 2009 demonstration, confirmed the industry’s ongoing reliance on manual controls.

“To date, very few domestic electrolytic aluminum factories have used the automatic approach to extinguish the anode effect,” the authors wrote in a study published in the academic journal Engineering Technology Research in 2020

Chen Xiping, a material science professor at Zhengzhou University in Henan Province, told Grid that anode effects have become less frequent with the use of some automated systems in the prevention phase, but that the reliance on the stick method persists. 

Along with those preventative measures, “companies also use [the stick],” Chen said. “Relatively few domestic companies use the automatic anode lowering  method.”

The authors of the 2020 study wrote that the use of automated control methods isn’t widespread because the necessary computer software hasn’t been widely installed.

However, David Wong, an aluminum industry expert with Atmolite Consulting in Brisbane, Australia who led the 2009 demonstration in China, said there is another reason why companies haven’t installed the software.

Wong said plant operators in China typically run their smelters with volumes of molten aluminum that are higher than what the aluminum pots were designed to hold.  If the anodes at the top of the pots were quickly dunked further into the pots to kill the anode effect, the pots could overflow. This would cause the molten salt at the top of the pot to spill out. Such an overflow could create an explosion hazard if the liquid level inside the pot dropped too low.

Wong said he has suggested to plant operators in China that they run their aluminum pots with less aluminum, but that Chinese companies decided to take a different course. 

Aluminum's Super Pollutants

Maintaining the proper chemical balance to maximize aluminum production efficiency is a constant challenge for aluminum plants worldwide. Further compounding the issue, plant operators in China run their smelters at a lower voltage than smelters elsewhere in the world to try to reduce energy demands and therefore cut costs, Wong said. But operating at lower voltage can compromise plant efficiency, increase PFC emissions, and make it harder to maintain a proper chemical balance, he said. 

According to Wong, extra molten aluminum is added as a way to mitigate the impact of some of the imbalances that would otherwise compromise production efficiency.

“When you operate with higher liquid levels, you can sometimes mask the problems,” Wong said. ​​“The problems go away—but problems return.  It’s a less efficient way of operating in our opinion.”

Where the Chinese Government Stands on PFCs

In November, the Chinese government released a plan for reining in carbon emissions in the non-ferrous metals sector, which includes aluminum. The plan contains a goal of getting 30 percent of electricity for aluminum production from renewable energy sources by 2030, and significantly increasing the amount of non-ferrous metals sourced from recycled materials in China by 2025. 

Any increase in recycling would reduce both energy needs and PFC emissions, but PFC emission reductions were not explicitly included in the measures.

Although the government hasn’t yet required aluminum companies to reduce the industry’s PFC emissions, the problem is on its radar. One sign: Chinese government guidelines for metals companies to voluntarily calculate their emissions included a formula for assessing PFC emissions. 

The rates recommended by the government agencies nearly a decade ago—and again in an updated document this year—are significantly lower than current emissions from Chinese smelters as estimated by the International Aluminium Institute, perhaps reflecting a lack of awareness of the companies’ antiquated methods.

Aluminum Emissions Leaderboard

Individual companies in China are not required to publicly disclose PFC emissions, making it difficult to track progress on pollution reductions.  

“More disclosure on emission hot spots or industrial-specific emission sources, such as PFCs emission for aluminum enterprises, are necessary to provide stakeholders, especially decision-makers and researchers empirical data to work on,” Lindsey Zhu, green supply chain senior project officer at China’s Institute of Public and Environmental Affairs,  told Grid in an email. 

U.S. officials are considering climate-related tariffs on steel and aluminum aimed at Chinese production, and European policymakers are inching closer to a broader “carbon border adjustment mechanism” that would apply to imported steel,  aluminum and other products. In time, these policies may put further pressure on Chinese aluminum makers to reduce their emissions. 

Millions in Savings From Automation 

In China today, it appears that at least one company, Henan Zhongfu, is making use of the automated method. In their study on the automated control technology, researchers at the company said they save an estimated 1,663,500 yuan, or approximately $240,000 per year, on electricity by using the automated method instead of the stick method. 

In addition, the study’s authors noted that the automated controls greatly reduce the need for all those sticks—nearly 8,000 of them at their facility each year—saving the company an additional 11,826 yuan, or approximately $1,700 annually.

If similar savings could be realized across all of China’s 88 aluminum smelters, the cost savings would come to approximately $21 million per year, based on an Inside Climate News assessment.

Tabereaux, who helped develop the automated control technology in the 1970s, said cost savings aside, it’s time China implemented the less polluting technology to rein in those “immortal gases.”  

“It makes me kind of think that what we’re doing in the U.S. and Europe doesn’t really amount to much compared to what China is doing,” Tabereaux said of the Chinese industry’s continued reliance on manual controls. ”The emissions they generate are so much more.”

Lili Pike is a China reporter at Grid focused on climate change, technology and U.S.-China relations. 

Editor’s note: An earlier version of this story attributed the 2016 survey of Chinese smelters to the International Aluminium Institute; it has been updated with correct attribution.