Mint Innovation, a startup company from Auckland, New Zealand, recently reported having succeeded in recovering gold, palladium and copper from electronic waste by exposing the material to microbes with a taste for the three metals. I spoke with Ollie Crush, the company’s chief scientist, to learn more about this process.
“The overarching goal is to come up with a lower capex / opex way of recovering precious metals from electronic waste”, said Crush. “You could then have decentralized plants compared to smelters that process large scales of waste. The advantage is more certainty for the aggregator, shorter time frames on payment, more transparency and a higher return of value from what they are collecting.”
The microbes are fairly selective in what they digest. According to Crush, they collect more than 90% of the gold, palladium and copper contained in printed circuit boards (PCBs), over 60% of the total value of the feedstock. The team is still working on expanding the selection capability to extract more of the most valuable components.
The precious metals are being retrieved from the loaded microbes by ashing them, another step that is still being optimized. Crush points out that developments into process refinements, and developments into other metals, are still limited because of the small size of the business. Mint Innovation are currently working on setting up a pilot plant in Auckland that would be capable of processing about 200 metric tons of PCBs per year using a 5,000 liter tank, yielding approximately 40kg of gold. The project is partially funded but the company is still seeking capital for the US$ 4-5 million plant.
A full size plant will be able to handle 10 times the volume, which is when larger markets than New Zealand will be needed to fully utilize the technology.