CM – How bacteria can extract precious metals from electric vehicle batteries

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June 17, 2021

by Sebastien Farnaud, The Conversation

There are more than 1.4 billion cars in the world today, and that number could double by 2036. If all of these cars burn gasoline or diesel, the consequences for the climate will be devastating. Electric cars emit fewer air pollutants, and if powered by renewable energy, driving wouldn’t add to the greenhouse gases that warm the earth’s atmosphere.

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But producing so many electric vehicles (often abbreviated as EVs) in a decade would drive demand for metals like lithium, cobalt, nickel and manganese. These metals are essential to the manufacture of EV batteries, but they are not found everywhere. Most of the world’s lithium lies under the Atacama Desert in South America, where mining threatens local people and ecosystems.

Leading electric vehicle manufacturers need to keep import costs down and find a reliable source for these raw materials. Mining in the deep sea is one possibility, but it could also damage habitats and endanger wildlife. At the same time, electronic scrap filled with precious metals is piling up in landfills and in some of the poorest regions of the world – 2.5 million tons are added annually.

EV batteries themselves only have a shelf life of eight to ten years. Lithium-ion batteries are currently recycled at a meager rate of less than 5% in the EU. Instead of mining new sources for these metals, why not reuse what’s already out there?

The largest lithium-ion battery recyclers are based in China. While recycling is often seen as an obligation in North America and Europe that businesses should be paid for, the competition for dead batteries in China is so intense that recyclers are willing to pay for it.

Most batteries that are recycled are melted and their metals extracted. This often happens in large commercial plants that use a lot of energy and thus emit a lot of carbon. These plants are expensive to build and operate and require sophisticated equipment to handle the harmful emissions generated by the smelting process. Despite the high cost, these systems rarely reclaim all valuable battery materials.

The value of the world market for metal recycling is expected to increase from 52 billion US dollars (37 billion pounds) in 2020 to 76 billion US dollars by 2025. Without less energy-intensive recycling methods, this emerging industry will only exacerbate environmental problems. But there is a natural process of extracting precious metals from waste that has been used for decades.

Bioleaching, also known as biomining, uses microbes that can oxidize metal as part of their metabolism. It is widely used in the mining industry where microorganisms are used to extract valuable metals from ores. More recently, this technique has been used to clean and reclaim materials from electronic waste, particularly computer circuit boards, solar panels, contaminated water, and even uranium heaps.

My colleagues and I in the Bioleaching Research Group at Coventry University found that all of the metals in EV batteries can be recovered through bioleaching. Bacteria like Acidithiobacillus ferrooxidans and other non-toxic species target the metals and recover them one at a time without the need for high temperatures or toxic chemicals. These purified metals are chemical elements and can therefore be recycled indefinitely in multiple supply chains.

In the scale-up of bio-leaching, bacteria are grown in incubators at 37 ° C, often using carbon dioxide. It doesn’t use a lot of energy, so the process has a much smaller carbon footprint than typical recycling plants while also causing less pollution. At the same time, bio-leaching systems reduce the waste of EV batteries and enable manufacturers to recover these precious metals on site and to rely less on the few producing countries.

Academics working on bio-leaching to stop once they’ve removed all of the precious metals from electronic scrap and are floating in solution. That’s not enough for industry. We combine bio-leaching with electrochemical methods that can fish out these metals and make them usable for supply chains. Unfortunately, metal recycling processes that have been in use for decades, which require a lot of energy and toxic chemicals. Industries cannot always afford to innovate, so it is up to the government to mandate change and invest in cleaner alternatives.

EV batteries are a technology that is still in its infancy. Reusing your components should be seen as part of their design. Rather than being an afterthought, bio-leaching recycling can become both the beginning and the end of an EV battery life cycle, generating high quality raw materials for new batteries at low environmental costs.

This article was republished by The Conversation under a Creative Commons license. Read the original article.

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