Ask Eartha: The scoop on biodegradable bags
December 6, 2012
At the town of Breckenridge’s open house on plastic bags, a community member suggested we switch plastic bags to biodegradable bags. What’s the deal with biodegradable bags and do they really break down?
– Concerned citizen, Breckenridge
It’s not a secret that we produce a lot of waste. From bottles to bags, plastic leftovers have been wreaking havoc on the environment and our trash cans for some time. For that reason, it’s no surprise that manufacturers are looking to technology to make plastic waste disappear.
True biodegradability facilitates decomposition by living organisms into something that is beneficial for the earth. More recently, a slew of “biodegradable” plastics including oxo-biodegradables, partially degradable, and recyclable-hybrids have hit the mainstream as the answer to all of our problems. Waste as much as you want because biodegradables will melt away like magic. Unfortunately, this perception and misleading marketing claims have outraged compost activists. Just because the label says biodegradable doesn’t mean it will recycle into nature.
So why the thumbs down on biodegradable plastic? First of all, the term “biodegradable” has been complicated with too much greenwashing. The biodegradability of a product depends on a number of factors including time, sun, moisture, air and microorganisms. For example, some biodegradable bags may break down into soil. Others may fragment into a million microscopic plastic pieces.
Biodegradable plastics claim to break down in your backyard or the landfill but the process of breaking down can take years, decades or forever. Also, biodegradable may actually refer to compostable where an industrial-sized compost facility is needed to reach high temperatures and moisture levels to transform that material into soil.
As you can see, biodegradable can mean many things – some good and some bad for the environment. The most alarming issues with biodegradable plastics are false claims that confuse the public and actually contaminate existing compost programs. Below are some technical but helpful definitions to decipher biodegradable and compostable plastics. You can usually find these terms stamped on the product label or directly from the manufacturer.
> Degradable – When exposed to excessive moisture and heat, degradable plastics will disintegrate into tiny pieces of plastic, polluting our rivers and soils. Thumbs down!
> 100 percent Recyclable and Biodegradable – The normal cycle of a biodegradable product is generally 90 days at an industrial compost facility (aka high heat). Products that are both recyclable and biodegradable often claim they will break down in one to five years. These hybrids are a mix of non-biodegradable plastic and a compostable material such as corn starch. Unfortunately, once the organic portion of the product composts, the remaining plastic fragments like other degradable plastics. Thumbs down!
> ASTM D6400 – This is a standard specification for compostable plastics. This certifies that the plastic is truly compostable in a municipal or industrial compost facility. It also signifies the entire product is consumed by microbes during the compost process with no persistent residues (aka fragmented plastic pieces). Thumbs up!
> PLA – Polyactic acid is a plastic substitute generally made from a plant starch like corn that’s an alternative to your average petroleum-based plastic cup or bag. Labeled as a recycling #7 symbol or “other,” PLA plastic slowly biodegrades within three months in an industrial composting facility (reaching at least 140 degrees in heat).
PLA plastic bags and cups can cause contamination problems in recycling programs because they are meant for composting. PLA is often associated with BPI and ASTM D6400 certifications. Depending on a number of factors including how the product is disposed of, where it is manufactured, and if it is 100 percent PLA, I give this product mostly Thumbs up!
> Oxo-biodegradable – A petroleum-based plastic product that breaks down when exposed to heat and oxygen. Often disguised as plastic carryout bags, oxo-biodegradable plastics should never be added to compost programs. Studies have found that even after several months in an ideal environment, the plastic did not break down. Thumbs down!
If in doubt, leave it out of the compost program. We don’t want to contaminate our community compost. You can always check biodegradable products against a third-party verifications process such as the Biodegradable Products Institute (Thumbs up!). BPI has a database of certified compostable products that are safe for the environment and our soils. Check it out at bpiworld.org.
Unless we can capture all certified biodegradable bags in our community compost program, I don’t think replacing plastic bags with biodegradable bags is the answer. The best way to reduce plastic bag waste is to not create it in the first place (BYOB – Bring Your Own Bag). You, too, can voice your opinion on plastic bags at EngageBreckenridge.com.
Ask Eartha Steward is written by the staff at the High Country Conservation Center, a nonprofit organization dedicated to waste reduction and resource conservation. Submit questions to Eartha at firstname.lastname@example.org.