With the rapid advancement of technology and electronics, e-waste is accumulating at an alarming rate around the world. A significant contributor to this e-waste stream is discarded printed circuit boards (PCBs) from computers and other electronic devices. PCBs contain a variety of metals, including copper, tin, lead and small amounts of precious metals like gold, silver and palladium. This has led many people to wonder – is extracting gold from circuit boards worth the effort?
How much gold is in circuit boards?
The amount of gold in circuit boards varies depending on the age and type of the device. Older electronics from the 1980s and 1990s tend to have higher gold content compared to newer devices. This is because gold was commonly used in connectors, fingers and traces on PCBs during that time. Here are some estimates of gold content in different circuit boards:
| Device | Gold content (grams per ton) |
|---|---|
| Motherboards (modern) | 200-300 |
| RAM sticks (modern) | 200-350 |
| Motherboards (vintage) | 500-800 |
| Fingers (vintage) | 1500-2000 |
| Connectors (vintage) | 2000-3500 |
As you can see, gold content is higher in older circuit boards, especially the fingers and connectors which were gold plated. Modern motherboards and RAM sticks have lower gold content since manufacturing processes have become more efficient over time, reducing the need for gold.
Extracting gold from circuit boards
There are several ways to extract gold from circuit boards:
Acid leaching
In this process, the circuit board is crushed and treated with a chemical leach, usually aqua regia (a mixture of hydrochloric acid and nitric acid). The acid dissolves the gold, separating it from the base metals. The gold can then be recovered from the leaching solution using electrowinning, carbon absorption or precipitation.
Smelting
Smelting involves heating the circuit boards to high temperatures to melt the metals and separate them. The precious metals, like gold, sink to the bottom while the lighter metals float to the top. This requires smelting equipment like furnaces, crucibles etc.
Mechanical separation
Mechanical processes like grinding, magnetic separation, density separation and shredding can be used to liberate precious metals from circuit boards. Gravity concentration methods are commonly used to recover liberated gold.
Each process has its own advantages and limitations. Acid leaching is effective at extracting gold but involves use of chemicals. Smelting can process bulk amounts of boards but requires high heat and off-gas treatment. Mechanical processing is simpler but the gold recoveries are lower compared to chemical leaching.
Is it profitable to recover gold from circuit boards?
Whether gold extraction from circuit boards is profitable or not depends on several factors:
Gold market price
The market price of gold fluctuates daily. As of October 2022, the price of gold is around $1650 per ounce. For gold recovery to be profitable, the price needs to be sufficiently high to cover your operating costs and make money.
Cost of processing
Extracting gold from circuit boards involves costs for labor, utility bills, chemicals, equipment etc. If your processing costs are too high, you won’t make a profit even if the gold price is high.
Efficiency of extraction
The percentage of gold you can extract from the boards also determines profitability. Chemical leaching can extract over 90% of the gold, while mechanical separation may only extract 50%. The more efficient your process, the more gold is recovered.
Type of circuit boards
As mentioned earlier, older circuit boards contain more gold. It is more profitable to process vintage boards compared to modern ones.
Economies of scale
Like any business, larger scale operations benefit from economies of scale. A large e-waste recycler who processes tons of boards a day using automated methods can extract gold more efficiently than a small manual operation.
What are the challenges of extracting gold from circuit boards?
Here are some key challenges faced in recovering gold from e-waste boards:
Collection and logistics
Sourcing sufficient volumes of e-waste boards can be tough. Transporting and storing the material also requires infrastructure and handling capacity.
Pre-processing
The boards need to be manually dismantled and sorted before processing. Other components like batteries, wires and metals may need removal. This is labor intensive.
Toxicity
Chemical leaching involves use of acids and other hazardous chemicals. Off-gas and wastewater treatment is required to make the process environmentally sound.
Variable content
Gold content varies across different circuit boards. Assaying and testing is needed to identify high-grade boards.
Technology investment
Specialized equipment like shredders, leach reactors, electrowinning cells etc. is required, involving major capital investment.
Compliance costs
Stringent regulations apply to e-waste recycling facilities regarding emissions, effluents, worker safety etc. This increases compliance costs.
Conclusion
Extracting gold from discarded circuit boards can potentially be a lucrative business if done right. However, it requires strategic planning, significant capital investment and advanced technical capabilities. The economics are most favorable for large, integrated e-waste recycling facilities that can achieve economies of scale and high metal recoveries through automated processes. Smaller operators may struggle with making profits if they lack the infrastructure, technology and volumes required to extract gold efficiently from circuit boards.
With the exponential growth in e-waste volumes globally, recovering precious metals from electronics continues to be an important activity. However, the hazardous nature of such recycling means following environmentally sound practices is a must. Overall, extraction of gold from circuit boards offers both business opportunities and sustainability benefits if carried out responsibly.