Bioleaching: Using bacteria to recycle precious metals from electronic waste

Electronics form the world’s fastest growing domestic waste stream. Outdated phones, surplus consoles, disused devices – all face the death knell each time a flashier product lights up an advertising billboard.

In 2019, the world generated 54.6 million tonnes of ‘e-waste’; equivalent to 350 cruise ships, or 7.3 kilograms per person. However, just 17.4 per cent of it was formally collected and recycled. Since 2014, the amount of e-waste recycled has grown by 1.8 million tonnes – a relatively small amount, considering that the amount of e-waste generated increased by 9.2 million tonnes in the same period.

Usually, rich countries in Europe and North America export e-waste to landfill sites in developing countries in Africa and Asia. According to the Global e-Waste Monitor – an annual review of e-waste – reports that, if the metals were widely recoverable, ‘e-waste’ would be worth $62.5 billion per year. That figure doesn’t even include the prized lithium from electric vehicle (EV) batteries.

Recovering a greater fraction of that supply would alleviate the strain on virgin natural resources. Global reserves of some elements, such as platinum, are anticipated to be fully depleted within 15 years if the proportion of recycled stocks entering production doesn’t increase. Yet, demand for metals is rising; lithium, cobalt, nickel and manganese most acutely, which are needed to produce EV batteries. As Geographical previously covered in the April 2020 edition, most of the world’s lithium sits under South America’s Atacama Desert, but human rights abuses are rife and local ecosystems suffer as new areas are explored and excavated. Recycling more of what’s already out there would reduce the environmental and humanitarian trade-offs of mining operations.

E-waste and EV batteries are currently recycled through processes called pyrometallurgy and hydrometallurgy. However, they involve searing temperatures with a high energy demand and deep carbon footprint, and toxic chemicals, harmful to the environment. Alternatives are therefore being sought.

A copper mine in Rio Tinto, Spain. Extracting copper from e-waste could mean that there is less need to excavate new mines in future. Image: Denis Zhitnik

A team of scientists from the University of Coventry are scaling up one such alternative. They have been using non-toxic bacteria to oxidise and recover the precious metals – a process known as ‘bioleaching’. They’ve shown that copper is widely recoverable from discarded e-waste, and that all metals present in EV batteries can be recovered using microbes. ‘Most of the time we are using very common bacteria that have evolved to oxidise metals as part of their natural metabolism; rarer bacteria that oxidise things like silver, gold and platinum can be readily cultivated,’ says leader of the ‘Bioleaching Research Group’, Sebastien Farnaud. ‘We’re working with methods that have been on Earth for billions of years and mimicking them to solve a modern issue: that’s essentially what all biotech does.’

If scaled-up, bioleaching facilities would mean that manufacturers of EV batteries and other electronic goods would be able to recover metals locally, relying less on costly exports to recycling centres abroad. ‘They would be less reliant on expensive mining operations as well,’ Farnaud says. The group are now the first to collaborate with an industry partner, N2S, which has begun scaling up the technology and is already using bioleaching to extract metals from printed circuitboards.

‘Often, when an industrial innovation sparks from an academic partnership, the industry side sees it as an add-on to resolve a given problem, which then goes away,’ says Farnaud. ‘But the key here is that the whole electronics market needs to change.’ He adds that currently, a key limitation for e-waste recycling is the lack of certification detailing the types and amount of metals contained in electronic goods. But with a robust and efficient recycling process on the horizon, manufacturers have the incentive to use more recycled material in their products, which will change the very design of electronics goods. ‘It’s about closing the loop of a product’s life cycle.’

Ultimately, bioleaching technology is borne from the ideal of creating a truly circular process for the things that we consume. ‘We need to shift from a mindset and economy where we see waste as an end product, to one where there isn’t even a start or an end at all.’