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E-Waste: The Role PCB Plays and Its Recycling

E-Waste: The Role PCB Plays and Its Recycling

Electronic waste or e-waste, or e-scrap, or end-of-life electronic waste, no matter what one calls them, are sprawling to be the world’s largest stream of waste. Wasted computers, smart phones, robots, automotive, or any other high end electronic gadgets when they reach the end of their life are disposed of. 

E-Waste: The Role PCB Plays and Its Recycling
Electronic Waste

However, e-waste is just a subset of such wastes with their own inherent value that can be reused, refurbished or recycled. Recycling of this subset of electronic wastes is a potential hunch in favor of both protecting the environment and intrinsic economic value. 

PCBs, a Contributor to E-Waste:

Electronic waste is an umbrella term including a plethora of different kinds of waste having various shapes and sizes, affecting the environment on different scales and having varied economic relevance. Some having hazardous components needs to be separated individually. 

E-Waste: The Role PCB Plays and Its Recycling
Used PCBs

One such major category of hazardous material and component is waste electronic and electrical equipment (WEEE) that has to be separately treated is printed circuit boards (PCBs). For instance,

  • In Printed Circuit Boards, lead, and cadmium are common in solder; cadmium occurs in certain components, such as SMD chip resistors, infrared detectors, and semiconductors
  • Further, Polychlorinated biphenyl (PCB) containing capacitors have to be removed for safe destruction. Lead and mercury occur in LCDs, especially for old designs. 
  • Liquid Crystal Display (LCDs) of a surface greater than 100 cm2 has to be removed from WEEE.
  • A large proportion of heavy metals such as lead, mercury, and cadmium are present in batteries that leach into the environment.

While these were some end-of-life waste generated via PCBs, PCBs also generate waste during its manufacturing process. We are aware the PCB manufacturing process is a complex process consisting of multiple steps. These includes: 

E-Waste: The Role PCB Plays and Its Recycling
Manufacturing Process Waste
E-Waste: The Role PCB Plays and Its Recycling
Percentage of Different Components

Don’t Waste the Waste:

Simply leaving these waste to decay naturally not only becomes a potential environmental pollution but also rules out the possibility of recovering valuable electronic components that either can be used directly or recycled and used indirectly. 

E-Waste: The Role PCB Plays and Its Recycling

PCBs have a ratio consisting of 40% metals, 30% organic materials, and 30% ceramics. Therefore, recycling processes recover approximately 99% of copper, copper-beryllium alloys, beryllium oxide, aluminium, tin, gold, silver, platinum, palladium, and lead from a PCB board. 

Why Recycle PCBs?

PCB recycling is done to eliminate negative impacts and harvest positive outcomes. 

E-Waste: The Role PCB Plays and Its Recycling

To eliminate negative impacts, such as:

  • Negative Externalities on Environment: If the PCBs are left to decay naturally in the open, it will take thousands of years to do so. The harmful fluids bleeding out of electronic components will contaminate the soil and water.
  • Prevention of Toxics Entering Food Chain: Through soil and water, the contaminants enter our food web and can result in fatal consequences both at intra and inter generation levels by affecting genetic makeup. 
  • Prevent Illegal Dumping of EWaste in Developing Countries and Water Bodies: The developed countries pass on the burden of safe disposal of hazardous e-waste on developing countries to cut cost on labour and treatment. The developing countries end up becoming the dumping ground of such electronic wastes. 

Similarly, industries unleash untreated e-waste directly into rivers, seas and oceans which result in toxics affecting marine life.

To harvest positive outcomes, such as:

  • Economic Worth of the Residue: Presence of high-grade precious metals (~28% weight) such as Au, Ag, Cu, Pt, Ta and others can be extracted for their higher value. 
  • Contributes in Slowing down Natural Resources Extraction: The metallic grade in PCBs is more than a hundred times of those in natural mineral resources. Further, it cuts overdependence on mining by circulating the same material again. 
  • Composites Extracted from PCBs: PCBs are commonly composed of fiberglass reinforced epoxy composites, electronic components, and various additives that can be used beyond single use life cycle. 

Is There a Safe Way to Recycle PCBs?

PCB recycling can be a tedious task as it involves separation of different types of electronic components that need different treatment. Direct incineration can result in release of toxic fumes like dioxins and lead into the environment. 

PCB recycling can happen at two stages:

At Manufacturing Stage: 

  • Recovering Copper Metal from Edge Trim- This is done using the two methods:-
    • Hydrometallurgy- Edge trim is first treated with a stripping solution to strip and dissolve precious metals, typically gold (Au), silver (Ag) and platinum (Pt). After adding suitable reductants, the ions of precious metals are reduced to metal form.
    • Mechanical Separation- After the precious metals recovery, the edge trim is further processed to recover copper metal. Due to difference of density, the copper metal particles can be separated from the plastic resin by a cyclone separator.
  • Recovering Copper Oxide from Wastewater Sludge- The wastewater sludge in the printed circuit board industry typically contains high amounts of copper (>13%, dry base). The recycling of the sludge is simple and straightforward. The general practice in the recycling industry is to heat the sludge to 600-750°C to remove the excess amount of water and to convert the copper hydroxide to copper oxide. 

At End-of-Use Waste Recovery Stage:

Currently, PCB recycling processes can be classified as thermal and non-thermal processing. 

  • Thermal Processing- It entails use of hydration, pyrolysis, and metallurgical methods. 
  • Non-Thermal Processing- Chemical treatment, disassembly, separation and shredding techniques are included. 
E-Waste: The Role PCB Plays and Its Recycling
Thermal and Non-Thermal Processes

These processes can be subdivided into three stages:-

  1. Pretreatment- It involves composition analysis and disassembly based on reusability and harmful content of the components. 
  2. Concentration and Separation- The recycling solution dissolves the thermoset substrate of the waste PCB; second, the electronic components including circuits, resistors, and capacitors etc. are separated from the circuit boards. 
  3. Chemical and Mechanical Refinements- Finally the material is extracted using various chemical processes like pyro metallurgy, hydrometallurgy and electrochemical processes or through mechanical procedures such as sorting. 

These are the basic steps that the PCB recycling process follows to retrieve valuable materials from the board that can be used in newer PCBs. However, PCB recycling is still a disjoint process where no large scale recycling is happening and leaves the gate wide open for start-ups to step in and come up with lucrative, efficient and safe innovative methods for PCB recycling

PCBs are here to stay, and their growth is projected to increase manifold in coming years. This is a déjà vu moment for the world, the late 20th century had plastic which was the talk of the day back then but plastic disposal talks never made it to the table. As a result today we live surrounded by plastic waste dumps everywhere; there is plastic gyre in the Pacific Ocean due to plastic dumping. Let’s not wait for the same consequences with e-waste and PCB waste disposal in coming years!

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