Using microbes, a New Zealand start-up extracts solid gold from e-waste

Wasim Raza

Every year, the world produces 50 million tons of e-waste – equivalent to 4,500 Eiffel Towers or 125,000 jumbo jets – produced from old computers, discarded screens, broken smartphones, and damaged tablets. As a rapidly growing waste stream, e-waste also contains metals important to tech that might become scarce soon.

With our increasing reliance on tech, reducing e-waste and conserving metals is becoming a key objective. The answer may lie with the tiniest of organisms: microbes. Microorganisms such as these can glean valuable metals from the electronics we bury in landfills such as cobalt, gold, and platinum.

Biotechnology and synthetic biology group leader Anna Kaksonen says microbes can facilitate processes that would otherwise require extreme temperatures and other conditions. It can often be a more sustainable process than traditional methods like pyrometallurgy or hydrometallurgy.

The waste that electronics produce contains a lot of precious metals, so why not use them to make precious metals? Can electronic waste be converted into gold?”

Mint Innovation, a startup based in New Zealand, is one company striving to mainstream microbes. Mint innovation begins with the circuit boards that are inside nearly every electronic device.

Thomas Hansen, the company’s commercial manager, says the company was inspired by the idea of microbes being able to turn waste products into something valuable. The waste that electronics produce contains a lot of precious metals, so why not use them to make precious metals?

What if we could make gold from electronics waste?

In addition, co-founder Will Barker previously worked for LanzaTech, which turns factory carbon emissions into fuel using bacteria. Both companies are based in New Zealand, where waste minimization is a priority. As gadgets get cheaper, manufacturers are learning how to build them with fewer precious materials. In addition to waste, the mint team is also studying other types of waste. These can be processed in the same way as car parts when it comes to solving the global problem of Ewaste.

Inside Mint’s pilot plant in Auckland. Photos: Mint Innovation

When it recovers gold from electronic components, the company grinds circuit boards, RAM sticks, processors, and other metallic parts into sand-like powder, which goes through a leaching process that results in a liquid that holds all the metal dissolved within it.

The first step is to dissolve reactive base metals, such as iron, copper, and aluminum, and then process them for recovery. The process of extracting metals with the aid of electric current is called electrolysis,” Hansen explains.

After that, the precious metal is extracted using microbes. Gold becomes easier to obtain once the base metals have been exhausted, says Hansen. Gold’s unreactive nature complicates chemical reactions because it dissolves very slowly — it is the final metal to disappear from solutions.”

In addition to aqua regia (Latin for “royal water”), a mixture of acids capable of dissolving gold, the team adds a microbe called Cupriavidus metallidurans. As tiny sponges, they absorb the dissolved gold.

After passing through a centrifuge, the solution is spun in a way that removes gold-heavy microbes. In this process, gold becomes purple on a nanoparticle level, creating a substance that looks a bit like Silly Putty. “There are a few impurities in it, but it is predominantly microbes and gold,” Hansen explains. Upon burning off these organic materials, a metallic ash is left behind that is processed through traditional metallurgical methods to become solid gold.

There is much more to precious metals than gold. According to Hansen, microbes love other metals, such as palladium, platinum, and rhodium. In addition to e-waste, we are also interested in waste streams that contain valuable metals, such as incinerator ash. Our chemistry might have to change slightly or we might have to use different microbes.”

After microbes are added, the solution has a vanilla ice cream-like texture.
The microbes absorb gold and produce a purple goo that resembles Silly Putty.

With e-waste and metals being recovered from local recyclers, Mint Innovation is looking to build biorefineries in cities. In Auckland, the company has a pilot plant that tests its processes on recycled IT equipment.

Scaling up and going global may be difficult, however. Alex Payne, a publicist for TerraCycle, says that “it may be challenging for a company to adapt to new regulations and navigate the complexities of local environmental policies.”

Because Mint Innovation still depends partly on chemical leaching, Mint Innovation must find a way to recycle its chemicals along with reducing waste and using less energy.

With this solution, we are able to pay recyclers more for their waste, giving them more revenue and allowing them to recycle more,” Hansen says. They are incentivized to recycle more, and we can have a positive effect by incentivizing better behavior.”  The small number of employees have limited contact with E-waste, keeping them safe from exposure to toxic compounds.

The company is planning full-scale facilities in Australia and the United Kingdom. This smaller plant in Auckland, New Zealand, was built to demonstrate how the Mint process works. It processes about one metric ton of circuit boards per week. But larger plants, like the one they’re building in Australia, will process 10 metric tons per day. That would make the bigger plan able to process about 1% of all the Ewaste Australia produces annually. The plant larger facilities will be almost entirely automated. The company says it sources all raw material from a local recycler exporting waste.




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