Biodegradable or Recycled Plastics?

I have always been a proponent that all biodegradable resources should be made use of and preferred to regular PET (polyethylene terephthalate) and HDPE (high density polyethylene). These last two are the most popular plastics used in households and industry. Biodegradable plastics are two kinds – one is a true degradable plastic containing polylactic acid (PLA) based on plant origins with corn being the most popular. The second type is produced by mixing in a special degradable additive into PET and HDPE.

Challenges come from the problem of how exactly degradable plastics degrade. It appears that there is a lot of fine print to that mixed in with some sophisticated marketing and simply burying bottles in a landfill might not do the job. What is more, some of the bio-based products are not degradable and definitely not over night or a short period of time. Others require a certain sequence of thermal processing to activate the degradable additives – another huge reason why we should never put any hot food in plastic unless it is specifically tested for heat. The ironic part here is that some petroleum-based plastics would degrade over time.

Naturally, there are economics involved. The objective of the recycling process is to produce high quality recycled resin which is competitive and/or easier to get than virgin material. For this to work, certain gathering technology and waste management practices have to be in place from curbside collection to sorting, transportation and baling etc. Once these plastics are separated at materials recycling facilities, involving a good percentage of manual work, they are then baled and ready to ship to a facility. To preserve the value of the plastics, i.e. to make it commercially usable and extend the life cycle, a closed productions loop is recommended.

A closed loop cycle suggests that best material for bottles is extracted from recycled bottles, the cleanest thermoforms come from recycled thermoforms and so forth. When the biodegradable plastic is thrown in the same recycling stream, problems are certain to follow shortly. Baled recyclate often has to spend some time en route exposed to various weather and conditions to which biodegradable mass might simply not respond well. This overall decreases the value of the recyclate and could lead to various consequences including worsened recycled resin. Once the cycle closes a few times the quality of the product can really go poor meaning that large amounts of plastics can end up in the landfills due to failing to conform to product specifications.

So what is the outcome of this recycling effort? Surely there is a lot of lobbying between manufacturers of plastics, packaging suppliers, retailers, government subsidized activities, recycling organizations etc. Maybe degradable plastics are not so good of an idea quite yet since we do not have the resources to separate them early enough and maintain PET recycling unimpeded. While I have always erred on the side of bio and organic packaging, all of a sudden now I am not sure! Maybe using regular plastics could be better since the recycling system is in place and has proven to work over the years. One way to identify plastic bottles is to look at the bottom for the SPI (Society of Plastics Industry) code – 1 normally stands for PET while all bio polymers or oxy-based material would go in the 7-Other category. In addition, some thermoforming-style plastics such as polystyrene (SPI code 6) are for the most part not recycled due to reasons of light weight or cheap petroleum-based raw materials.

In summary, I believe I might switch back to glass bottles. For water, maybe I will buy one of the filter pitchers and hope to be safer with tap water. Best solution for end consumers might be to limit consumption and handle the garbage disposal problem in this fashion. Now with the new emerging markets approaching middle class and the ambitious plans of all beverage makers to get a piece of these new economies - consumption will likely increase instead.

Sources:

http://www.dordan.com/pdf/dordan_recycling_report.pdf

http://www.napcor.com/pdf/DegradablesSept2009.pdf