Expert:innen: Andreas Blatter (PX Group), Alexandra Levesque (PX Group)
Extracting gold from electronic waste using bio-based methods sounds like the dream of a 21st-century alchemist. Now, Swiss gold processor PX Group is demonstrating in a pilot project that this actually works. It becomes clear that electronic waste is not just a problem, but also a valuable resource that should be exploited.
There are many positive stories to tell about digitalisation, such as people being able to stay in contact with family and friends even when they are on the other side of the world. Or how it has been used to make production processes safer and more efficient. However, it’s been difficult to find anything positive to say about the electronic waste that this generates. Until now, that is.
In 2022, 62 billion kilograms of electronic waste were generated worldwide – equivalent to 7.8 kilograms per person. The problem is not only the sheer volume, but above all else the speed at which it is growing. In the twelve years between 2010 and 2022, the amount of electronics disposed of annually increased fivefold. In Europe, around 40 percent of electronic waste is correctly fed into the waste stream and subsequently recycled. However, the remaining 60 percent is incinerated together with household waste and other refuse or ends up in landfills.
Yet this electronic waste consists of valuable raw materials: 50 percent metals, 30 percent plastics and 20 percent other materials, including rare earths as well as silicates, glass and substances that are environmental toxins.
It all began in 2020 with the decision to secure primary access to gold as a recyclable material. “We used to buy gold,” commented Andreas Blatter, Director of Research and Development at the PX Group. “Some watch manufacturers would give us the precious metal so we make semi-finished products from it. Today, we want to have our own access to gold. The aim is to do this in as ethical and environmentally friendly a manner as possible.” As it turned out, this wasn’t as simple as it sounded initially. So the PX Group focused on extracting gold from waste streams.
Areas that are now being developed as gold mines typically contain 0.5 to 1 gram of gold per tonne of rock. Smaller mines can have a gold content of up to 25 grams of gold per tonne of rock. In contrast, electronic waste contains between 30 and 100 grams of gold per tonne of material. If electronic waste were a gold mine, today’s refineries would be fighting tooth and nail for access to it.
Processing electronic waste has its own pitfalls and is neither simple nor cheap. The simplest – though not the most environmentally friendly – approach to handling is to incinerate the waste. The metals are left behind, and the gold can be extracted from the residues. This approach is standard practice today. However, not only does it consume unnecessarily large amounts of energy; it also produces large amounts of greenhouse gases and other toxic gases. Moreover, this recovery process creates a considerable mountain of hazardous waste that is difficult to clean up and is usually sent to landfill. Besides the ecological problems, this process also makes no economic sense, as Andreas Blatter explains, because the electronic waste is transported over long distances before being incinerated and fed into the smelting process.
The PX Group relies on a decentralised process – one that is used where the electronic waste is generated. First, the electronic waste is sorted. Plastic and metal parts are separated. The metal is then crushed by a mill. This ground electronic scrap is placed in a tank together with a solution. A biogenic substance – one produced by bacteria – dissolves the gold from the ground material. The contents of the tank are then filtered with a resin, which traps the gold. When the dried resin is finally incinerated, the gold remains as a residue.
The biogenic substance used in the PX Group’s process is produced by bacteria cultivated by Brain Biotech. They ferment a sugar solution into a liquid capable of dissolving gold. It is relatively pH-neutral and does not need to be disposed of as hazardous waste. This enables the PX Group to avoid the strong acids and other highly toxic substances used in gold extraction. Many mines destroy entire ecosystems. Soils and waterways suffer from the effects of the substances used even years after mines are closed. From the very outset, the PX Group’s efforts have been aimed at developing a process that avoids hazardous waste.
Alexandra Levesque, Head of Innovation and Development at the PX Group, emphasises that the process works and is technically feasible. Now, it is a matter of scaling up the process and establishing a network of partner companies so that economic viability can be proven too.
Globally, 20 to 30 tonnes of gold could be extracted from electronic waste every year. While this is only a small fraction of the gold needed worldwide, the economical processing of electronic waste could also provide important impetus for material cycles in other industries, because, as the PX Group’s process shows, waste contains valuable substances.
