What are common methods for recycling polymers?

Common methods for recycling polymers include mechanical recycling, chemical recycling, and energy recovery.

Mechanical recycling is the most common method used for recycling polymers. In this process, the polymers are sorted, cleaned, and then shredded into small pieces. These pieces are then melted and reshaped into new products. This method is often used for recycling common polymers such as PET (polyethylene terephthalate) and HDPE (high-density polyethylene), which are typically found in plastic bottles and containers. However, the quality of the recycled product can be lower than the original, as the polymer chains can break down during the process.

Chemical recycling, also known as feedstock recycling, involves breaking down the polymer chains into their original monomers or other useful chemicals. This is usually done through processes such as pyrolysis (heating in the absence of oxygen), hydrolysis (reaction with water), or glycolysis (reaction with glycols). The resulting monomers can then be purified and used to make new polymers. This method can potentially produce higher quality recycled polymers than mechanical recycling, but it is more complex and energy-intensive.

Energy recovery is another method used for recycling polymers, particularly those that are difficult to recycle or contaminated with other materials. In this process, the polymers are incinerated to produce heat, steam, or electricity. This method can help to reduce the amount of waste going to landfill and provide a source of renewable energy. However, it also produces greenhouse gases and other pollutants, so it needs to be carefully managed to minimise its environmental impact.

In addition to these methods, research is ongoing into new ways of recycling polymers, such as enzymatic recycling, which uses enzymes to break down the polymers into their constituent monomers. This could potentially offer a more sustainable and efficient way of recycling polymers in the future.