Quartz 4

Recycling and Issues Related to Recycling Plastics

4 min read

Recycling Plastics

  • can be carried out using physical method or chemical method

→ before recycling is carried out: plastic waste needs to undergo pre treatment → this is because not all plastics can be recycled. → recycling method for diff. types of plastics can be different.

Pre Treatment of Plastic Waste Involves:

  • sorting by diff. methods (e.g. manual sorting, sorting by density)
  • washing to remove contaminants
  • shredding or grinding to smaller pieces

Physical Method

Physical method of recycling plastics is known as mechanical recycling

  • using this method → chemical composition of recycling plastics remain unchanged

after pre treatment → small pieces of plastics such as Poly(ethene) are melted, cooled, pulled into long thing strands, and cut into pellets

  • these pellets can be made into new products.

Chemical Method

chemical method of recycling plastics converts plastic waste into diff. raw materials through diff. chemical reactions

Cracking

  • plastic waste such as Poly(ethene) waste, can undergo cracking to form short chains of Alkanes and Alkenes.
  • short chained alkanes can be used as fuel
  • short chained alkenes can be used to make other useful chemicals (chemical feedstock and other chemical substances)
  • cracking requires high temperature and presence of catalyst

Depolymerisation

  • polymer can be converted back to its monomers
  • after depolymerisation → monomers can be converted to other useful chemicals

Definition

Depolymerisation is a process in which polymers are broken down into their monomers #ChemistryDefinitions

Polymers can undergo depolymerisation through acid hydrolysis involves breaking down a polyester using water in the presence of an acid catalyst. products are the monomers used to form the polyesters - a dicarboxylic acid and a diol

  • polymers such as polyester can be depolymerised by breaking the ester linkages using water in the presence of an acid catalyst. this is acid hydrolysis

polyethylene terephthalate (PET) → is a polyester used to make plastic bottles.

both physical and chemical methods can be used to recycle PET waste.

graph LR
	Monomers --> PET
	PET --> Waste_Materials
	Waste_Materials -->|physical method| PET
	Waste_Materials -->|chemical method| Monomers
  • some plastic waste may be recycled using both physical and chemical methods

imp to minimise pollution caused by disposal of plastic waste. diff ways to minimise plastic waste:

  • first reduce plastics we use, and reuse plastics for same or new purpose
  • if reducing and reusing are not possible → we should recycle the plastic object instead of throwing it away

Env Issues of Recycling Plastics

both physical and chemical methods of recycling plastics may lead to env. issues. e.g. if wastewater generated from the recycling process is not treated properly before being discharged into water bodies - it can contaminate water and cause pollution.

Econ Issues of Recycling Plastics

  1. recycling plastics can be expensive - costing much more than disposal in landfills or incineration

    • there is cost of transporting waste to the processing plant
    • there are also costs of sorting and cleaning waste, and carrying out either physical or chemical recycling processes
    • all processes involved in recycling plastic waste - require manpower, machines and energy

  2. may not be worthwhile or economically viable to recycle plastics if cost of recycling plastic waste is higher than the value of the recycled plastics.

    • recycled plastics usually have lower market value than virgin plastics that are made from raw materials and not obtained from recycling processes. means that they are sold at lower value than virgin plastics
    • will be difficult for recycling businesses to survive if the costs of recycling plastic waste is too high

Social Issues of Recycling Plastics

  1. in SG - many ppl find it more convenient to throw all their waste away. as a result, recyclable plastics are disposed of and are not recycled

  2. many ppl are not aware of the proper way of recycle plastics. when recycling is not carried out properly → plastic waste in recycling bins may not eventually get recycled

    • when recyclable items such as plastic container are contaminated with leftover food, the recyclable usually end up being incinerated and not recycled
    • non recyclable items - including types of plastics - are sometimes thrown into recycling bins. this increases time and effort to separate recyclables from the waste - and slows down recycling process.

  3. takes time and effort for communities to adopt recycling as a lifestyle - so it might not be immediately effective

  • strict measures and laws must be put in place to minimise potential env. issues.
  • recycling programs can be introduced to educate public on the correct way to recycle plastic waste.
  • creative activities can be introduced to encourage people to practice recycling.
  • give incentives to encourage recycling efforts.

Graph View

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