Electronic waste in landfills, namely PCBs, can provide up to 150 grams of gold per ton – much more than natural deposits.
A gold extraction involves environmental challenges and complex processes. Removing small amounts of gold from natural ores requires a lot of machinery, large amounts of water and dangerous chemicals like cyanide. The yield from this Herculean effort is somewhat modest, with around ten grams of gold extracted from one ton of ore.
However, municipal waste, specifically thrown away electronic devices, offers a more efficient and profitable source of gold and other valuable metals, writes the .
Os electronic waste, also known as e-waste, These include items such as old cell phones, computers and household appliances, which, in total, amounted to around 62 million tons worldwide in 2022, according to the UN.
A significant part of this waste contains printed circuit boards (PCBs), which are rich in materials such as gold, silver, palladium and copper. With PCBs to offer around 150 grams of gold per tontogether with other recoverable metals, the total value can exceed 20 thousand dollars per ton, far exceeding traditional returns from gold extraction.
Despite the high value of these materials, less than 25% of electronic waste is recycled. The most common recycling methods involve burning PCBs in furnaces or treating them with strong chemicals to extract metals, processes that generate high carbon emissions and toxic byproducts.
As such, companies are developing cleaner and more sustainable techniques, including the use of bioleaching. This is a process that uses bacteria to extract metals.
Certain bacteria, such as Acidithiobacillus ferrooxidansmetabolize materials to produce oxidizing agents, which dissolve metals in solutions. These dissolved metals can then be recovered through various methods, such as filtration or electroplating.
Already Bioscope Technologies, a company in England, bioleaching has been optimized for urban mining. By carefully controlling the environment for bacteria – maintaining acidity, heat and oxygen levels – the process can extract metals from crushed PCBs in just a few days.
Gold precipitates easily with a little water, while copper is recovered. The bacteria, which are safe and non-pathogenic, are then reused in the process, making the system sustainable and efficient.
Bioscope Technologies’ facilities have the capacity to process one thousand tons of PCBs per year, with plans to expand in the future. Its process recovers almost all of the gold, silver, palladium and copper, ensuring that the precious materials can re-enter the supply chain for use in new electronic products.
The company is also exploring ways to recover other materials, such as tin, zinc, gallium and tantalum. Testing is already underway, with full production expected to begin in January.
