High oil prices led to large price hikes in the price of polyethylene and polystyrene this fall. Even if the high resin prices aren’t sustained, a side-effect has been renewed interest in plastics made from agricultural sources (i.e., corn). Once a fringe product, Ag plastics are getting attention from major retailers and makers of food and consumer goods. This should be of concern to recycling managers (see below).
The stand-out example is Wal-Mart Stores Inc. The Bentonville, Arkansas-based retail colossus announced this fall that it plans to use corn-based plastic to make containers for strawberries, herbs, cut fruit, and various products such as bread bags, donut boxes and gift-cards. The biodegradable material will be supplied by NatureWorks LLC, a subsidiary of Cargill Inc. based in Blair, Nebraska. NatureWorks 300 million-pound-capacity plant derives polylactide resin (PLA) by converting starch distilled from corn into natural plant sugars, which are in turn fermented into lactic acid.
A Wal-Mart spokesperson said that PLA plastic helps hedge against fluctuating oil prices and makes it easier to project packaging costs. Wal-Mart also thinks PLA is “the right thing to do” where the environment is concerned. The company estimates that using 100 million PLA containers per year will save the firm the equivalent of 800,000 gallons of gasoline and reduce greenhouse gas emissions by 11 million pounds.
Wal-Mart’s backing represents a huge market boost. NatureWorks’ sales in the first six months of this year tripled from the same period a year ago and the company has averaged 45 percent growth in the last four years.
How this material will impact recycling systems, prices, compost operations and the whole post-consumer market is not yet understood.
NatureWorks is attuned to the potential for its PLA to upset the recycling apple cart, and has already announced its intention to buy back “degradables” collected and sorted from conventional plastics in order to minimize their negative impact on the recycling of conventional resins.
Yet who will do this sortation? Householders are already confused about what plastics go in their recycling containers. Will they (and their municipalities) be able to identify these new products and separate them? And is PLA really so advantageous from an environmental lifecycle perspective in the first place?
On June 2, at the 31st Annual RCBC Conference in Harrison Hot Springs, B.C., Jim Cairns of Environmental Plastics Advisory Services (EPAS) made an excellent presentation on degradable plastics that summarizes their evolution. (His PowerPoint slides are available under the Posted Documents button atwww.solidwastemag.com)
This class of plastics has been around for about 20 years. Initial experiments with the addition of starch proved ineffective and tainted the image of degradables.
The next generation of degradable plastics fall into two major types: biodegradable plastics (“Bio’s”) and Oxo-biodegradable plastics (Oxo’s). Bio’s can be made from fossil fuel sources or agricultural sources, and offer one-step bio-degradation. Oxo’s are modified with additives for “controlled life” and degrade in two steps: disintegration and then biodegradation.
“Closed loop” charts of the lifecycle of Bio’s are appealing to environmentalists, playing up the conversion of the sun’s energy into plants, the distilling and use of the product, and its eventual composting (where the whole cycle begins again). Professional organizations promote performance standards to allay concerns about product integrity. (The main ones are the Biodegradable Plastics Institute [BPI] and the OxoBiodegradable Plastics Institute [OPI].)
Cairns’ presentation concluded that Bio’s and Oxo’s will no doubt enjoy niche markets, but they could create as many problems as they resolve, and are not likely a panacea. At one point, the Canadian Plastics Industries Association (CPIA) and its Environmental Plastics Industries Council (EPIC) referred to degradables as having “limited friendliness” on their new website www.myplasticbag.ca (Also seewww.plastics.ca/allplasticbottles) These associations publicly encourage more recycling of conventional plastic grocery bags.
Important questions remain.
Is conversion of degradable plastic film or bags to compost really more “friendly” than conversion of exceptionally thin-gauged, exhausted, contaminated, conventional bags or film to clean energy using advanced thermal treatment (or recycled into plastic lumber)? And is the composting of a degradable rigid plastic item, after one use, more environmentally sound or sustainable than mechanically recycling the material to the limits of its intrinsic engineering properties, then doing same?
And what technical challenges will this material present to MRFs if it becomes ubiquitous? Again, it’s very decent of NatureWorks to offer to pay for skids of the material, but can it be separated, and at what cost? What machines will be required?
I don’t know the answers to these questions, but I think we need a lot more information before we follow Wal-Mart’s lead and start “growing” our packaging materials, as appealing as that might sound.
Guy Crittenden is editor of this magazine. Email Guy at firstname.lastname@example.org