Biodegradable vs Compostable: What’s The Difference?

By Susan Cho, Board Member

Have you gotten the hang of what you can compost with respect to food waste and yard waste? Hooray! Now there’s a growing trend towards more responsible product packaging. Double hooray! But it can be confusing when things are labeled either “compostable” or “biodegradable.” These are not interchangeable terms; not everything that biodegrades is compostable.

Biodegradable materials are broken down by living organisms, not artificial additives. The decomposition may or may not involve oxygen, and it may or may not yield useful material. Yes, plastics fall into this category.

A subset of biodegradable materials are compostable. Under the right conditions, they break down into nutrient-rich soil within 6 months. They need not just living organisms, but also oxygen, water, and heat.

Some products are classified as “backyard compostable.” Gardeners and biodiversity enthusiasts can toss them in their own piles/bins with glee. Other items are labeled for “municipal” or “commercial” systems. These can be composted by services such as Takoma Park Public Works or the Compost Crew. “Industrial” systems are extremely uncommon, because they involve far more management so they can break down things like meat, dairy, and bio-plastics.

Note that when compostable materials are thrown out, they end up in landfills/incinerators, so they do not yield compost. The benefit in such a case is that they were generally produced with less objectionable materials. This is why I choose biodegradable items even if I throw them out. Dog poop bags are a good example of this, since animal waste should not be used for compost.

These days, some completely plant-based scrub brushes, toothbrushes, dental floss(!), and lip balm or deodorant tubes are certified compostable. You can find them at zero waste stores like FullFillery, in downtown Takoma Park. Look for BPI certification, which ensures ASTM compliance (no, I don’t know what the acronyms stand for). Be aware that small vendors can’t afford 3rd party certification (like small farms might not have “organic” certification, even if they use organic methods), so they only label their product as “biodegradable,” even if it’s compostable. It’s worth asking the vendor personally.

I hope this has been informative and helpful!