Refining for EVs will hugely degrade air quality – unless we stop it

Electric vehicles (EVs) have been considered pivotal in the energy transition, offering a promising means to retain modern lifestyles without emitting greenhouse gases.  

However, recent research from Princeton University has investigated the refining of critical minerals like nickel and cobalt for battery production in countries such as China and India. 

They indicate that if these countries fully domesticize their EV supply chains, national emissions of sulfur dioxide (SO₂), a threat to pulmonary and cardiovascular health, could increase by up to 20%.  

Why does refining for EVs release sulfur dioxide 

Nickel and cobalt are typically extracted from sulfide ores; pentlandite for nickel and cobaltite for cobalt.  

When these ores are processed, particularly during smelting, the sulfur within the ore reacts with oxygen in the air to produce sulfur dioxide (SO₂). 

In some regions, particularly where environmental standards are less stringent, flue-gas desulfurization is not effectively implemented within the refining process. 

Worsening poor air quality in China and India 

When SO₂ is emitted, it reacts in the atmosphere to form either ammonium sulfate or simple sulfate aerosols, types of fine particular matter (PM2.5). 

China and India already suffer dangerous concentrations of fine particulate matter, with approximately 1.4mn premature deaths in China and 1.7mn in India attributable annually (2019). 

As such, increasing SO2 emissions by 20% poses the risk of a similar increase in fatalities, pushing China’s premature deaths up to 1.7mn and India’s to 2mn. 

How much are China and India investing in EVs? 

China has an established domestic supply chain for EVs, necessitating urgent efforts to mitigate SO₂ emissions from battery-metal smelting. 

By contrast, India is in the early stages of supply chain development, presenting an opportunity to build a cleaner, more sustainable system from the ground up.  

For both countries, the single most important and most practical step would be to enforce the use of flue-gas desulfurization. 

Avoid sulfuric battery-metals to protect air quality 

Lithium iron phosphate (LFP) batteries are both less toxic and cheaper, since iron and phosphate are abundant – but lower energy density limit their utility for EVs. 

However, iron remains a carbon-intensive metal that’s always in demand. Phosphate is critical for agriculture, and misuse risks continued overshoot of a key planetary boundary,  

Sodium, too, is more abundant than lithium, prompting Chinese manufacturer CATL to invest in sodium-ion batteries, claiming 160 Wh/kg for their first generation. 

Monitoring to protect public health from reckless growth 

The struggle to seize control of this emerging market is likely to incentivize disregard for air quality, even after regulation. 

In the absence of regional or global agreements, it is simply too likely that government will look the other way in the interest of development. 

Extensive monitoring infrastructure and investment in mitigation must be paired with international agreements that can hold producers accountable to their populations.