Understanding the basics of Plastics and how plastic waste could sit in landfills for evermore.

Plastic, one of the most abundant elements of our trash

Plastic products are an everyday part of our lives, so much so that many of us don’t give it a second thought. Found in almost everything we deal with, from packaging to containers, from household products to garden products, at work, in our cars and much more.

In fact, plastics make up around 12% of our trash ( Municipal Waste), that’s over a 1000% increase per year since the early 1960’s. Unfortunately, the recycle rates are low too and it is estimated that less than 10% of household plastic materials actually make their way for recycling. Here are some figures from the latest annual figures available on the EPA website:

·         31 million tons of plastic waste was generated in America in 2010

·         14 million tons were plastic containers and packaging

·         A milk jug will have a degradation time in a landfill of an estimated hundreds of years.

What are the type of plastics and how do we recognize them?

There are two categories for plastics, these are known as thermoplastic or as thermoset.  A thermoplastic softens when subjected to heat and is used in most of the containers, packaging trays and coverings we see in our everyday lives. Thermoset plastics solidify when heated and set hard, car dashboards and fenders are a great example of this technique.

The symbols used on plastics as identifiers for recycling are either the recycling triangle symbol with a number in the center or with the identifier initials for the plastic. These are normally found on the base of a container.

#1 #1 PET or PETE denotes polyethylene terephthalate resin. Plastic packages made with this type of plastic include water, soda and vinegar bottles along with prescription containers and film backing.

#2 #2 HDPE is high-density polyethylene resin. Common containers with this symbol include dish/clothes soap, bleaches, softeners, milk, hair care products, motor oil and some toys.

#3 #3 V denotes vinyl/polyvinyl chloride resin. Products that carry this symbol include various cooking oils, shrink-wrap, pipes, shower curtains, coffee containers and vinyl dashboards.

#4 #4 LDPE is low-density polyethylene resin. This type of plastic is known for flexibility and used in bread, grocery and sandwich bags, as well as flexible container lids.

#5 #5 PP denotes polypropylene resin. Items displaying this symbol include some food containers, syrup bottles, jar lids, food containers, diapers and outdoor carpet.

#6  #6 PS is polystyrene resin. This group includes disposable cups and cutlery, fast-food foam boxes, meat trays, packing peanuts and Styrofoam insulation.

#7 #7  A wide variety of plastic resins that don't fit into the previous categories are found in number 7. A few are made from polyactide (organic) and are compostable. Polycarbonate is also number 7, and is the hard plastic that has shown it can leach potential hormone disruptors and has many parents worried.

 
Biodegradable plastics.

Before we go into degradation times in landfills, I want to discuss biodegradable plastics. The normal plastics that we handle, i.e. PET and HDPE etc., are manmade and will sit in a landfill for hundreds of years in to the future.

But scientists and the plastics industry found that by adding certain substances, when placed in landfills, the microbes of the bacteria present will attack the additive. This action will also break down the plastic polymers and for the most part, will allow the bacteria to degrade the plastic substance also.

The FDA have approved the use of these additives and biodegradable plastics for use with foods.

Degradation times in landfills.

The truth is, there no set times for degradation, all of the numbers being quoted are theoretical, in my article about landfills, I wrote about researchers from the University of Arizona excavating a landfill after 15 years and readily identified hotdogs and other food stuffs due to the lack of moisture etc. Degradation time has several factors that speed up the process or can slow it down. Temperature of the landfill, moisture content ( which bacteria thrive on), oxygen and also sunlight.

The whole principle of a dry landfill is to keep moisture out in order to prevent leachate escaping into the soil around and causing pollution. Again, the landfills are capped to prevent rainwater entering the landfill, so once again sunlight is not going to be present for the most part. Temperatures should remain fairly constant due to the degradation and decomposition happening inside the landfills. However, in parts of the United States, where prolonged periods of cold weather occur, the overall temperature can have a detrimental effect on the landfill for that time.

We do know that thin biodegradable food wrap will be expected to degrade in about 2 months, the thin biodegradable water bottles within a couple of years. But the heavy milk jugs, the biodegradable plastics may degrade in 30 years or so, but this is only theoretical. The normal HDPE container would be expected to not break down for hundreds of years.

Summary

A lot of time and research has been spent and is ongoing with plastics. One big advancement has been the recycling of plastics for use in plastic lumber and I can only applaud this discovery and wish I had known about it when I built my porch some years ago.

The problem appears to be, in a lot of rural areas, that the price for plastic remains relatively low, and the prices I have seen quoted range from 12 cents per pound and 20 cents if sorted into the different types of plastic. In my area of Louisiana, my nearest company (120 miles away) also requires a minimum of 5000 lbs. weight. When up against aluminum that fetches 50 – 70 cents per pound, at any quantity and at any scrap metal yard, you can understand why this does not appeal to many as an economical  proposition.

The only sensible way forward would be for all of us to do a bit of research of our own and make an effort to get these plastics into a recycle program. There has been a lot of research in capturing the methane produced in decomposition, plastics are a big contributor to this, and when the benefits are much greater than the affects to the environment, I will become an ardent supporter. So for the foreseeable future, I support keeping plastics out of the landfills as much as possible, at least until a consistently safer way of extracting the energy is found.