Electronic waste is one of the fastest growing solid waste streams in the world. The emerging technological advancements and connecting most of our life with automation is leading to a substantial need of electronic products. Recovering precious metals from electronic scrap is an increasingly important practice in sustainable recycling, as it helps reduce the demand for mining and minimizes environmental impact.
Our dependence on technology and electronics has increased in last few decades by introducing automatic AI controlled cars, automatic machinery, automatic home appliances, computers, mobiles, IT equipment, internet devices and medical equipment.
In 2022, an estimated 62 million tons of e-waste were produced globally and it is rising five times faster than documented E-waste recycling and possibly reaching 82 million tons, in 2030.
According to a report by United Nations Institute for Training and Research UNITAR, The Global E-waste Monitor shows that we are currently wasting US $91 billion in valuable metals due to insufficient e-waste recycling. The figure does not include another millions of tons of e-waste stored in homes, warehouses and other which is illegally exported.
Despite international regulations targeting the control of the transport of e-waste from one country to another, its transboundary movement to Low & Middle Income Countries (LMICs) continues frequently and mostly illegally.
In March 2024, The UNITAR issued a report foreseeing a drop in the documented collection and recycling rate of e-waste from 22.3% in 2022 to 20% by 2030 due to the widening difference in recycling efforts relative to the staggering growth of e-waste generation worldwide.
Multiple Challenges contributing to the widening gap include technological progress, higher consumption, limited repair options, shorter product life cycles, society’s growing electronification, design shortcomings, and inadequate e-waste management infrastructure.
Electronic Waste Management Practices
E-waste streams contain valuable and finite metals and materials that can be reused if they are recycled appropriately. E-waste has therefore become an important income stream for low income people. On the contrary, if not recycled appropriately it can release hundreds of different chemical substances into the environment, including known neurotoxicants such as dioxins, lead and mercury which are critically harmful for pregnant women and children.
The e- waste also include some base metals and precious and rare earth metals like Neodymium, Gold, Silver, Tin, Copper, Nickel, and Palladium. In 2024 only, the value of precious metals extracted from e-waste has been estimated $15 billion globally. The world’s demand for critical metals (CMs) is anticipated to increase by 400 to 600 percent in the coming decades.
In United States there are many professional recycling solution providers with corporate social responsibility commitments ensuring data security and sustainability. The main responsibility there is to destroy and erase the data for corporate security and reliability. To date, 25 states and the District of Columbia have passed e-waste related legislation where it is illegal to dispose of hazardous waste in the garbage.
How they Process E waste
Electronic waste comes in a variety of shapes, sizes, and complexity which means that the extraction and recovery process cannot be uniform for all devices. That is why, the sorting and recycling process here is more complex and requiring several processing steps before the metal extraction process can begin.
Physical/Mechanical separation
The first step in the sorting process involves disassembling the electronic device into smaller components and removing hazardous components. Disassembling process typically requires a large amount of intensive manual sorting of materials before moving on to the next step.
However more autonomous disassembling and sorting methods are being developed. For example, Apple has recently developed “Liam and Daisy” robots which are capable of disassembling multiple iPhones at once and recycling components for reuse. This reduces labor costs and simplify the sorting phase.
Physical Separation and Processing
The next step is physical processing to convert metal-containing components into smaller fractions. This however, has a number of major limitations that prevent its large-scale use. The sorting methods produce a high potential for losing precious metals and not recovering metals to high purity. Additionally, there are high operating and energy costs to using these methods.
Shredding or pulverization alters the shape of metals and non-metals. Some metals take on a spherical shape under pressure, while non-metals remain nonspherical. This shape effect alongside different specific gravities can be taken advantage of in order to separate different fractions.
Liquid-based sorting uses the different specific gravities of metals and non-metals to sort into fractions. Processed Printed Circuit Boards (PCBs) are placed into a liquid solution, often tetrabromoethane or acetone. The non-metals float nearer the surface while metals sink near the bottom.
Electrostatic separation
This process separates materials based on the ability to conduct electricity. Non-metal fractions that do not conduct are sorted out using a vibration screen. The limitation of this method is that it is limited to only small particle sizes.
Magnetic separation is used to recover ferrous metals, such as copper. Magnetic separation is only effective when done prior to crushing. Magnetic separation is performed first and followed by crushing and then undergoes electrostatic processing.
Metal Extraction through Pyrometallurgy and Electrorefining
After the mechanical separation is completed, there are three different and typically complex options for further feed processing that are currently being used to recover both precious and base metals from PCBs. Smelting is currently one of the most commonly used processes where up to 70% of PCBs are treated in smelters. Here, crushed PCBs are incinerated and smelted in furnaces to reach at optimum melting point.
This method also partially removes the impurities. As a result, a low-concentration Platinum Group Metal (PGM) alloy is produced which requires the base metals to be removed before the PGMs can be processed.
The recovery of base metals from integrated smelters is limited to copper because iron and aluminum become concentrated in the slag produced. PCBs also contain ceramics and glass which contribute to higher slag formation, leading to a greater loss of recoverable precious and base metals.
On top of the high energy consumption, smelting has a high risk of dioxin formation releasing hazardous toxins. However, there are sophisticated treatment processes to control their discharge into the atmosphere.
Electrorefining the E waste
An additional step required for further metal processing is electrorefining. Here, anodes are cast from smelted, molten alloy and pure copper cathodes are produced in the electro-refining cells. During the electrolysis, copper will dissolve into the solution and plate in its pure form as a copper cathode. Noble metals like gold and PGMs do not dissolve into the solution but fall to the bottom of the cell (or anode bag) generating anode slime every 15-20 days.
Other less noble metals dissolve at the anode but do not plate well, resulting in impurities build-up and electrolyte contamination which requires bleeding to maintain copper cathode quality.
Digestion + Electrowinning of the E Waste
Another route for recycling Waste Electrical and Electronic Equipment (WEEEs) is digestion combined with other purification technologies. This method uses a combination of caustic or acid leaching followed by a purification technique. Acid leaching is the most common method to extract valuable heavy metals for resource recycling and environmental protection.
There are several different metal purification techniques including cementation, ion exchange, solvent extraction, activated carbon adsorption, and electrowinning.
The digestion stage is preceded by preprocessing of PCBs into non-ferrous particles that may contain various metals including gold, silver, copper, and PGMs. During the digestion, the copper is digested while the gold, silver, REE (Rare Earth Elements) and PGMs come out as a residue in less than 24 hours and can be further recycled into pure metal or sold to precious metal refineries.
Summary
Inappropriate handling of e-waste represents a loss of financial opportunity and contributes to global warming. If metals from e-waste are not recycled, more investment is required in mining and refining operations to generate primary metals. Mining however, is likely to become more expensive due to a decrease in metal grade in ores.
The matter needs more attention of both the government and communities as the global value of raw materials in the e-waste generated in 2023 was equal to approximately $62 billion, but we only managed to recover only a small fraction of it due to insufficient recycling.
The proportion of undocumented recycling should also be addressed and controlled. The transboundary movement of WEEEs also needs to be controlled internationally.
United States is already recycling close to 40% of its electronic waste. On the other hand, since 2014, the number of countries that adopted some form of regulation of e-waste is increasing, however, in many cases the enforcement is poor, and recycling is not done properly.
Governments are also looking into forcing manufacturers to recycle their own products where they are being asked to invest in making products which are more easily recyclable.
For a more sustainable future, envisioning a world without e-waste is essential.
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