Recycling Plastics

Importance of Recycling Plastics

Recycling plastics is crucial for reducing the amount of waste sent to landfill sites. Plastics take hundreds of years to decompose, so recycling helps to minimise environmental damage.

It conserves natural resources by reducing the need for raw materials like crude oil, which is used to make many plastics. This helps preserve finite resources for future generations.

Recycling plastics also lowers pollution. Manufacturing new plastics produces greenhouse gases and other pollutants, so recycling reduces these emissions. Additionally, recycling uses less energy than producing new plastic from raw materials, which helps to reduce the overall carbon footprint.

Types of Plastics for Recycling

Plastics are broadly divided into two types based on their behaviour when heated:

• Thermoplastics soften when heated and can be reshaped multiple times. This makes them easier to recycle mechanically.
• Thermosets harden permanently when formed and do not soften on heating, so they cannot be remoulded or recycled by melting.

Common recyclable plastics include:

• PET (Polyethylene Terephthalate) 6 used in drinks bottles and food packaging.
• HDPE (High-Density Polyethylene) 6 used in milk bottles, detergent containers, and pipes.

Plastics are identified by recycling codes, usually numbers inside a triangle symbol on packaging. These codes help sorting facilities separate plastics for recycling:

• 1 6 PET
• 2 6 HDPE
• 3 6 PVC (Polyvinyl Chloride)
• 4 6 LDPE (Low-Density Polyethylene)
• 5 6 PP (Polypropylene)
• 6 6 PS (Polystyrene)
• 7 6 Other plastics

Sorting plastics correctly is important because different types have different melting points and chemical properties, affecting how they can be recycled.

Recycling Processes

The recycling of plastics involves several key stages:

• Collection and Sorting: Plastics are collected from households and businesses. They are then sorted by type, often using automated machines that detect recycling codes or by manual sorting.
• Mechanical Recycling: This involves shredding plastics into small flakes, washing to remove contaminants, then melting and remoulding into new products. This method is mainly used for thermoplastics.
• Chemical Recycling: Also called depolymerisation, this breaks plastics down into their original monomers or other chemicals. These can be purified and reused to make new plastics. Chemical recycling can handle plastics that are difficult to recycle mechanically or are contaminated.

Mechanical recycling is more common because it is simpler and cheaper, but chemical recycling is gaining interest for dealing with mixed or contaminated plastics. Mechanical recycling is best for clean, single-type plastics, while chemical recycling can handle mixed or dirty plastics by breaking them down chemically.

For example, PET bottles can be mechanically recycled into fibres for clothing or new containers, while chemical recycling can break down mixed plastic waste into useful chemicals.

Example: If 1000 kg of PET bottles are collected and mechanically recycled, the plastic is shredded, cleaned, melted, and remoulded into pellets. These pellets can then be used to make new bottles or polyester fibres.

Environmental Impact of Plastic Recycling

Recycling plastics saves a significant amount of energy compared to producing new plastics from crude oil. For example, recycling PET saves about 70 680% of the energy required to make new PET.

This energy saving reduces the carbon footprint, meaning fewer greenhouse gases are released into the atmosphere. This helps combat climate change.

However, recycling plastics has challenges:

• Contamination: Plastics must be clean and sorted properly. Contaminants like food waste or mixing different plastic types can spoil recycling batches.
• Degradation: Plastics can degrade during recycling, losing quality and strength. This limits how many times they can be recycled mechanically before they must be disposed of or chemically recycled.

Despite these challenges, recycling plastics is still far better for the environment than producing new plastics or sending waste to landfill.

Example: Recycling 1 tonne of HDPE plastic saves approximately 1.5 tonnes of CO 2 compared to producing the same amount of new plastic from crude oil.