GREEN GREENER AND GREENEST
WHEN IT COMES TO PLASTIC BAGS?
What plastic bags harm the planet least?
Overall, biodegradable seems to be the greenest solution, although degradable or oxi-degradable bags offer important green benefits too. The choice is complicated because three of the four bag types have both good and bad characteristics when it come to their environmental impact.
The four types are:
• Conventional petroleum-based plastic bags, clearly the worse choice
• Compostable bags
• Biodegradable bags
• Degradable bags
Conventional vs. Biodegradable Bags
The city of San Francisco recently banned the use of conventional plastic bags in grocery stores within the city limits. Other states are considering similar legislation. The anticipated new laws have sparked questions about the various claims bag manufacturers make.
Conventional bags have few benefits. We all know the huge pressure they put on America's landfills, oceans and roadsides. We use tons of them...literally tons.
The term “biodegradable” is misused and misunderstood because it's a fact that everything biodegrades given enough time. Even polyethylene plastic bags will degrade with enough heat, time and light. But the amount of time, heat and the light needed for common plastic bags doesn't satisfy our need for eco-friendly resource management. The steel Titanic is biodegrading on the ocean floor yet the fact that it hasn’t completely decomposed in a 100 years suggests how inadequate the term “biodegradable” is.
To be considered biodegradable, the decomposed remnants of the grocery or trash bag must be ingestible by bacteria and microorganisms. These complete a process that produces CO2 and H2O. as biodegradable bags fully decompose. Because they decompose relatively quickly, biodegradable bags help cut pressure on landfills. That's the good news for biodegradable bags. On the downside, many biodegradable bags are corn based, so grain has to be diverted from a world food supply that's already falling due to dreadful global weather thanks to climate change. (World grain production dropped about 2% in 2010 when the world needed a boost of 3% in grain production.)
Degradable (or Oxi-degradable) Plastic Bags
Here's where degradable or oxi-degradable bags being to shine. Compostable bags only properly biodegrade if sent to a composting facility. A special organic composting facility is required for compostable bags to quickly decompose. Discard them on the side of the road as litter and compostable bags remain an eyesore for years because they will not biodegrade rapidly without the proper conditions.
Degradable bags or oxi-degradable bags (as opposed to biodegradable bags) use a technology that accelerates the degradation process of polyethylene bags. Bags are made with additives that make them turn brittle and fragment in about 18 months. Within 30 – 36 months, depending on the amount of oxygen and heat they get, degradable bags decompose into very small fragments of polyethylene powder—a kind of “polymer sand." But that's as far as degradable bags deteriorate while biodegradable bags are completely ingested by microorganisms.
On the other hand, anywhere roadside litter is a concern, degradable or oxi-degradable bags have a major benefit. We dump two billion pounds of plastic bags annually and as litter, degradable bags are better for the environment than conventional plastic or compostable bags. Why? Because degradable bags left clinging to trees or thrown along the roadside fragment must faster than biodegradable bags, so that they are no longer an eye-sore, faster.
I didn't mention that the reusable woven polypropylene bags, the kind given out by major grocery chains and mall stores aren't perfect either. The EPA recently found that of 71 bags tested from 44 major retailers, lab work found that reusable bags of 21 major chains contained lead levels above 100 parts per million–the maximum permitted by many states. (By the way, most of the lead was found in the bag's bottom liners, so if in doubt, remove them from your reusable shopping bag.)
What does it all mean? That there is no single, perfect "plastic" grocery or trash bag. Each of the different "eco-friendly" solutions has some benefits the other types lack.
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