Bioleaching, a technique that uses bacteria to leach precious metals from electronic waste, could help to create a circular economy in areas without established recycling plants. Overall, bioleaching has several advantages over conventional chemical leaching including lower cost, lower impact on the environment, lower hazardous characteristics of waste, lower energy demand as well as absence of toxic chemicals. Is this the future of e-waste recycling? Research teams across the world are investigating the potential of bioleaching in recycling e-waste, including a PhD student at NTNU.

E-waste (electronic equipment waste) is the most rapidly growing waste stream in the world, with over 50million tonnes generated globally each year. However, just 17.4 per cent of it was formally collected and recycled. At the same time, the amount of e-waste is rising three times faster than the world’s population.

Usually, rich countries in Europe and North America export e-waste to landfill sites in developing countries in Africa and Asia. Millions of people across the world are thought to work informally recycling these materials through open burning, exposing themselves and the environment to toxic fumes which then find their way into the water supply and food chain, poisoning animals and humans. In countries that do not have as good schemes for EE recycling as Norway, EE waste still ends up in landfills. There, toxic metals can leak out and seep into the groundwater, to the detriment of both nature and the population.

As of today, pyrometallurgy and hydrometallurgy are the technologies used to extract and recycle EE waste metals. These are energy-intensive processes where one must also handle and neutralize any gases and chemicals associated with recycling.

Fortunately, there are some smart researchers who want to find a solution to the problem. One of them is postdoctoral fellow James Mwase from NTNU in Trondheim. He believes in something called bioleaching – a method that was first linked as a possible solution to e-waste by a research team at the University of Coventry.

How does it work? Simply put, there is the use of microorganisms to help leach out valuable metals from sulfide minerals, he explains. Or in other words, the microorganisms chemically change the metal and release it from the surrounding rock. This allows it to dissolve in a microbial "soup" where the metal can be insulated and cleaned. The process requires very little energy and has a small carbon footprint. No toxic chemicals are used either, making it environmentally friendly and safe. Furthemore, The microorganisms are naturally occurring (often found during mining, in hot springs or volcanic areas) and hence do not need to be constructed in laboratories. This makes it rather simple for a microbiologist to collect the bacteria for it to grow in the laboratory and thereafter be used as a recycling mechanism. This might create massive opportunities in areas where there are no established recycling plants, but large amounts of e-waste.

The research team has been using non-toxic bacteria to oxidise and recover precious metals from e-waste. 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. Bioleaching is an eco-friendly and cost-effective technology for processing low-grade and complex ores and may also be an important bioremediation technology for processing solid waste and secondary resources such electronic waste. However, large-scale commercial applications of bioleaching are still developing slowly.