You’ve probably seen them on plastic containers, the little numbers contained in a three-arrowed recycling symbol triangle. These are a code that tell you what sort of plastic you have. They were started in the late 1980s by the plastic industry to help with recycling.

There are seven codes and they’re listed below.

1. Polyethelene or PET – polyester fibers, pop and water bottles and the plastic straps that hold bundles together
2. High-density polyethelene or HDPE – the hard plastic found in bins, equipment and other rigid plastics
3. PVC – water and electrical pipes
4. Low density polyethelene or LDPE – plastic bags, tubing and some bottles
5. Polypropelene – ducting, auto parts, food containers
6. Polystyrene – styrofoam, rigid knick-knacks, video cases
7. None of the above – yes none of the plastics above.

There has been some bad press lately about whether or not recycled plastics actually make it into the recycled waste cycle. Whenever a batch of plastics become hopelessly contaminated with dirty or off-type plastics, it will end up in a landfill rather than being reborn as a recycled product.

That said, more often than not, plastics really do get recycled. Those items with the #2 designation according to the Resin Identification numbering system are the most widely accepted. Such plastics include the most commonly used types of soda pop or water bottles. Though plastics tend to pay a far lower rate per ton than other types of recyclables, often the price paid for other recycled materials is sufficient to subsidize plastics.

The greater concern is probably the practice of sending plastic for recycling on huge journeys to Asia, at high fuel and carbon costs. This also bites into the overall energetic savings of recycling plastics.

In the 1970’s plastic replaced glass due to the petroleum crisis and the expense of glass, also there’s no movement in glass, so breaks easily. Throughout the mid 20th century there was nothing wrong with plastic, but now that isn’t the case.

Plastic releases a huge amount of toxic substances when incinerated if there’s no exhaust control which adds to soil and air pollution.

Now some plastics are known to cause problems, like baby feed bottles and containers, so are now being replaced by glass.