Image: Flickr, stevendepolo
Another claim for "sustainable bottled water" landed in the in box today. Leaving aside the merits of publicizing a Berkshire mountain water as "locally sourced" via an international forum like TreeHugger, it is the claim of an "environmentally friendly packaging" that demands review. Usually a quick once-over lands these claims in the virtual trash.
But this press release has something new: a plastic bottle that will decompose in landfills or municipal composting, and which is also recyclable. Is it possible that biodegradable plastic has reached the breakpoint where the benefits are outweighing the risks? And what does all of this have to do with spaghetti?In the past, we have been sceptical of compostable plastics for creating a false sense of responsibility or for false claims of biodegradability. Early attempts at eco-friendly plastics were no more than normal plastic seeded with starches that allowed the plastic to break up into invisibly small plastic particles, not really a benefit and introducing a big unkown regarding the potential effects of a lot of small plastic particles in the environment.
How Does the New Biodegradable or Compostable Plastic Work?
The breakthrough heralded in this press release is the use of ENSO bottles. ENSO claims that their bottles are "biodegradable in both landfill and compost environments and can also be successfully mixed with standard PET plastic recycling." How is that possible?
This is where the spaghetti comes in. Plastics are all long chains of atoms, strongly bonded together to give them great technical properties like the ability to withstand a charge of high-pressure carbon dioxide or contain water without breaking down even when you forget the bottles in the trunk of your car on a sunny day. These long chains are called "polymers".
You know how hard it is to eat spaghetti? Well, polymers are like spaghetti to microbes. Very few microbes have developed knives (called enzymes in micro-world) which can cut through polymer chains. And the chains are just too long for the microbes to get their mouths around. (Having already risked entering annoying analogy territory, we will leave off anthropomorphizing micro-mouths.)
Chemists were faced with a real challenge: how to develop a new plastic as strong and moldable as traditional plastic but which can be eaten by bugs living in landfills or compost heaps. The challenge is being answered with a new bag of tricks. The trick being used by ENSO is to pepper the polymers with additives that do two things: 1) attract the microbes, which otherwise don't think of plastic as "food;" and 2) help break the polymers down into bite-size pieces, allowing the microbes to attack and digest a bottle in 250 days under ideal landfill-like conditions -- as opposed to 500 years for traditional plastics.
The Risks of Degradable Plastic
It sounds like a great breakthrough, right? But there are still some negatives to throw into the lifecycle analysis:
1) Increased consumption: Consumers will use more disposable plastics. This means more resources -- whether petroleum or corn or other raw material for the plastic as well as energy and water and more -- go into making single-use throw-away goods.
2) Greenhouse gas balance: much of the carbon in the biodegradable plastics will be emitted as CO2, or worse, as methane (which has a much stronger greenhouse effect than CO2). Is freeing up landfill space really worth releasing all that formerly petroleum-bound carbon into our warming atmosphere?
3) Toxicity of breakdown products: because polymers start out as long chains, it is very important to ensure that none of the smaller pieces that occur as part of being broken down by microbes are toxic in their own right. ENSO has done testing and reports that all steps on the breakdown chain have no negative impacts on the environment. But in the race to get new plastics to the market, testing and caution must be the rule.
So is Biodegradable Plastic Good or Bad?
Biodegradable plastics are just one more tool in the waste management box. Particularly for hard-to-recycle plastic wastes, such as when plastic is bonded to other materials to provide a grease or liquid barrier, these new plastics are a bonus. The entire container can be designed to biodegrade and become a managable waste rather than a straight-to-landfill item. But accepting biodegradable plastic as a silver bullet is premature.
Native Waters, LLC, which is heralding "sustainable bottled water," may have their hearts in the right place, and folks around River Falls, MA, may find that Native Waters are the eco-preferred choice. But we need to keep our nose to the grindstone before bottled water can be tagged "sustainable."
As for ENSO, they can be praised for having an excellent FAQ on the issues facing their industry. And for taking one more step on the long path to sustainability. Let's keep walking.
More on Biodegradable and Compostable Plastic
TH Forums: Recyclable vs biodegradable vs compostable?
Compostable and "Biodegradable" Plastics Provide False Sense of Responsibility
Perf Go Green Biodegradable Plastics - Not So Biodegradable After All
Ecoflex® Compostable Plastic Packaging Materials By BASF