Degradable versus biodegradable plastic
May 20, 2008
First its important to distinguish between degradable and biodegradable.
The following was taken from http://www.noplasticbags.org
Degradable plastic includes all classes of degradable plastic including the biodegradable and compostable. However, plastic that is not biodegradable or compost able usually use the label Degradable plastic. Most of the products using the label Degradable plastic, degrade as result of physical and chemical impact (fracture into smaller pieces of plastic). Biological activity is not a significant part of the degradation of these products, or the process is too slow to earn the classification Biodegradable or Compost able (the biological degradation will typically take many years).
As you may know, the co-op store is all for degradable plastic. They use it for carrier bags and much of its food wrapping. The following is taken from their website..
The special additive used to make the polythene film degradable was initially developed in conjunction with, and extensively tested by, VMB, part of British Polythene Industries (click here to visit their web-site www.bpipoly.com). Parkside Performance Films, who supply the bags to the Co-op’s bread supplier, were then able to commence supplies of the degradable bread bags, after proving that the material had no detrimental effects on their production, the packing line or indeed the bread itself.
The additive is added as a part of the production process to allow total degradation of the plastic material, leaving only water, a minimal amount of carbon dioxide and a small amount of minerals compatible with soil. The technology has been independently tested and proven to be environmentally safe, leaving no toxic substances at the end of the degradation process. The material has also been tested as safe for direct food contact under EU standards.
http://www.co-op.co.uk/foodretail/index.php?pageid_grp=122.
Indeed the additives that help the plastic break down are often natural as in the case of starch.
From http://www.mindfully.org
“ Three generations of starch-based plastics are recognized. The first generation consists of a synthetic polymer. Starch is only used as a filling These bags are not fully biodegradable, though, since they consist of mainly non-biodegradable synthetic polymers like polyethylene or polypropene and only 5-20 percent starch. Under special conditions the starch degrades and the plastic falls apart into small particles, that will prevail for many years although they are not visible.
In the second generation the starch is used for its polymeric properties.
50-80% starch can be used in these plastics, but still a large part is not biodegradable.
The third generation is a truly biodegradable plastic, that does not contain synthetic polymers at all. To improve some of the properties of the plastic, the biopolymer may be modified, but no synthetic materials are necessary.[
source: Wageningen University University for Life Sciences, Department of Agrotechnology and Food Sciences. Processing of Agricultural Raw Materials for Non-Food Products. P050-217. http://www.ftns.wau.nl/agridata/historybiodegrplast.htm 27oct01
Rather than take centuries for the product to break down it take years or months – the time it takes is built into the bag.
It breaks down into miniscule particles of plastic.
Just to remind you why plastic bits are not so good.
“ plastic is made by combining many toxic synthetic man-made chemicals by a process called polymerization. The plastics industry tells us that this process binds the toxic chemicals together so tightly that they are no longer toxic to us. But they don’t tell us that the polymerization process is never 100% perfect. It always leaves some of those toxic chemicals available to migrate out of the plastic product and into whatever contacts it—your food, you, air, water, and so on.
Degradable Plastic
April 15, 2008
Degradable plastic is specially designed to break down more quickly than normal plastic. Plastic does not biodegrade or rot – in fact it lasts for centuries so we are now knee deep in indestructible litter.
Degradable plastic is made from minute particles of plastic so small as to be invisible. The particles are bound together with a chemical or biodegradable additive
The additive breaks down within a determined time frame releasing the small particles of plastic resulting in a pile of plastic dust.
The plastic particles will last as long as plastic does – decades, centuries, millennium – we don’t actually know.
What is known is that the plastic particles released are now small enough to be absorbed into the surrounding environment the soil water table and so the food chain with unknown results.
Follow the link for more detailed information.
What I think is ….
Why go to the effort of making degradable plastic bags when we already have naturally compostable products such as paper bags and cornstarch bags. Why not use plastic for things we don’t want to rot away like drainpipes and use naturally biodegrading materials for disposable packaging?
