Ask Eartha: A guide to recycling plastics (column) |

Ask Eartha: A guide to recycling plastics (column)

Dear Eartha,

I recently moved here from Austin. I took my recycling to one of the county’s recycling drop-off centers and noticed that they only accept #1 and #2 bottles. In Austin, I was able to recycle #1 through #7 plastics. Why is it different here? Are there some plastics that are more easily recycled? — Monica, from Breckenridge

Thanks for the question, Monica. You are correct, there are some plastics that are more easily recycled than others. There are specific reasons for this but first, a brief chemistry lesson on plastics.

In a process called polymerization, plastics are created by treating components of crude oil or natural gas. This “cracking process” creates hydrocarbon monomers, which are linked together in long chains. There are two groups of plastics: thermoplastics and thermosets. Most plastics are thermoplastic, which means once they are formed, they can be heated and reformed repeatedly.

So what do the numbers on the bottom of the container mean? The #1 though #7 designation simply has to do with what type of plastic it is and the materials or resins that it contains. These are the most common types of plastic resins and I have listed them as follows:

#1 Polyethylene Terephthalate (PET) — Commonly used in food packaging because of its strong barrier properties against water vapor, dilute acids, gases, oils and alcohols. PET is shatter resistant, slightly flexible and easy to recycle.

#2 High Density Polyethylene (HDPE) — a rigid, tough and strong resin of natural milky color. HDPE has very good stress crack resistance as well as high impact and melt strength.

#3 Polyvinyl Chloride (PVC) — PVC containers offer clarity, durability and chemical resistance. Primarily used for household goods containers such as soaps and cleaners, chemicals and personal care items.

#4 Low-density Polyethylene (LDPE) — dry cleaner garment bags and produce bags. Widely used in wire and cable applications.

#5 Polypropylene (PP) — Ketchup bottles, yogurt containers, medicine bottles, pancake syrup bottles and automobile battery casings.

#6 Polystyrene (PS) — comes in many shapes and forms, from foam egg cartons and meat trays, to soup bowls and salad boxes. Typically called Styrofoam.

#7 Other plastics — a catch-all for all other plastics.

To make things more confusing, there are different processing methods, which also affects how easily they are recycled. They are as follows:

Extrusion — Plastic films and bags are made by extrusion processing.

Injection molded — Process used to make products such as butter tubs, yogurt containers, closures and fittings.

Blow molded — This process is uses to make carbonated soft drink bottles.

Rotation molding — Used to make hollow products such as toys or kayaks.

So back to your question: Why can’t our Materials Recovery Facility take plastics other than #1 and #2 bottles? Recycling must be somewhat profitable. So, when our recyclables go to the Materials Recovery Facility (MRF) at the landfill, they are sorted and sold by the ton. There are MRFs all over the country, and they all sell their recyclables this way. The more profitable the MRF, the more likely people can continue recycling. The prices of these commodities are always changing, so sometimes things change as far as what is accepted and what is not. The guidelines for what to do with your waste really depends on your locale. For example, rural communities like Summit County have limitations on what they can recycle because it is more difficult to haul materials.

The plastics industry designed various types of plastics, including hybrid plastics without regard for recyclability. Simply put, there aren’t reliable collection and processing systems for number 1 through 7 non-bottle plastics. Additionally, mixed plastics (#1-7) are economically unsustainable to recycle. By recycling mixed plastics in past years, our county’s recycling program made 70-80 percent less than what they would have made if they collected only #1 and #2 bottles. Why? Because there are no local markets for #3-7 plastics. Most of them are being shipped to China.

When you think of the costs and carbon footprint of shipping plastics to China for recycling, then it starts to look less appealing from an environmental and socially-responsible standpoint. China does not have human and environmental regulations like we do in the U.S., and there are fewer ways to track what really happens to recycling. The responsible thing to do is to use local markets and not to ship our resources overseas. The reason that corrugated cardboard, newspaper, #1 and #2 plastic bottles, etc. are commonly collected materials is that there is a recycling infrastructure — processors and manufacturers who want these materials and make them into products that are sold for profit and sold locally. Without this infrastructure — or market — recycling cannot be sustained.

So please, do not throw anything other than #1 and #2 plastic bottles when you take them to the recycling drop-off centers. We appreciate those who recycle properly and understand the limitations.

Ask Eartha Steward is written by the staff at the High Country Conservation Center, a nonprofit organization dedicated to waste reduction and resource conservation. Submit questions to Eartha at

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