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Environmental Science
Plastic Waste Lifecycle
Production to Landfill to Ocean
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Plastic waste begins long before a bottle, bag, or wrapper is used. Most plastics are made from fossil fuel feedstocks such as crude oil and natural gas, which are extracted, refined, and chemically converted into small molecules called monomers. These monomers are joined into long polymer chains that can be molded into lightweight, durable products. The same durability that makes plastic useful also makes plastic waste a long lasting environmental problem.
Key Facts
- Most common plastics are made from petroleum or natural gas feedstocks.
- Polymerization joins monomers into polymers, such as ethylene molecules forming polyethylene.
- Global plastic recycling is about 9 percent, while much more is landfilled, burned, or released into the environment.
- Mass balance: plastic produced = plastic in use + recycled plastic + landfilled plastic + incinerated plastic + leaked plastic.
- Degradation time for many plastics can be hundreds of years, depending on material, sunlight, oxygen, and temperature.
- Mixed-resin plastics are difficult to recycle because different polymers have different melting points and chemical properties.
Vocabulary
- Feedstock
- A raw material, such as crude oil or natural gas, used to make chemicals and products.
- Polymer
- A large molecule made of many repeating smaller units called monomers.
- Single-use plastic
- A plastic product designed to be used briefly before being discarded.
- Microplastic
- A plastic fragment smaller than 5 millimeters that can form when larger plastic items break apart.
- Ocean gyre
- A large system of rotating ocean currents that can concentrate floating plastic debris.
Common Mistakes to Avoid
- Thinking all plastic with a recycling symbol is actually recycled. The symbol often identifies resin type, but recycling depends on local collection, sorting, contamination, and market demand.
- Assuming plastic biodegrades like food waste. Most plastics mainly fragment into smaller pieces rather than being rapidly broken down by organisms.
- Mixing different resin types and expecting easy recycling. Different plastics can melt or react differently, which lowers the quality of recycled material or makes processing impossible.
- Counting incineration as the same as recycling. Incineration may recover energy, but it destroys the material and can release greenhouse gases and pollutants if not tightly controlled.
Practice Questions
- 1 A town discards 12,000 kg of plastic waste in one month. If 9 percent is recycled, how many kilograms are recycled and how many kilograms remain for landfill, incineration, or leakage?
- 2 A factory makes 2,500,000 plastic bottles, each with a mass of 18 g. What is the total mass of plastic produced in kilograms?
- 3 Explain why a plastic bottle can move through several possible paths after use, such as recycling, landfill, incineration, or ocean transport, and why the mixed-resin problem makes the recycling path harder.