Biodegradable and compostable sound like interchangeable terms, but if we really care about the end product, the devil is in the details.

We can all agree that every carrot is a vegetable, right? But it certainly doesn’t follow that every vegetable is a carrot, that would be ridiculous. Similarly, although everything that is compostable is biodegradable, not everything that is biodegradable is compostable. You may be one of the many people who use the two terms interchangeably, but there are some key differences that create an important distinction between them.

Biodegradable

“Biodegradable” is a blanket term for anything that is able to be broken down (degradable) by bacteria or other living things (bio). Biodegradation involves bacteria and other microorganisms using the product in question as an energy source and transforming it into a variety of byproducts, including carbon dioxide, methane, and water. The important thing to remember about biodegradation is that it doesn’t stipulate any kind of timeframe or environmental conditions. 

As long as this breakdown occurs, it can take as long as necessary – even if a material takes 20 years to be converted into byproducts via bacteria, it is still considered just as biodegradable as something that does so in 30 days. And even if the material requires an extremely specific and bacteria-rich environment, and would not biodegrade in simple soil conditions, it is still considered biodegradable because it could, theoretically, eventually, biodegrade. 

Additionally, biodegradable as well as oxo-degradable bags, for instance, are often just plastic bags with additives put in to eventually break the plastic down over time. This means that the final product will still be plastic, just in smaller pieces, and the bag cannot be put in your green composting bin with your food scraps and yard trimmings without contaminating everything in there. Technically though, this is still considered biodegradable because the product degrades with the help of living organisms. Not as tough as you’d think to meet those requirements, huh?

Compostable

The word “compostable” on the other hand, is much more choosey. For a product to be certified compostable, it has to meet ASTM (American Society of Testing and Materials) standards. This means that the product must be tested and approved in a third-party laboratory, not just by the company trying to sell it. Independent scientific analysis must confirm that the product does not contain high amounts of regulated metal, that it biodegrades quickly under composting conditions, and that the final product is able to sustain plant life. Notice how these requirements include the environmental conditions and rate at which the product must biodegrade. 

So if being termed biodegradable is like getting into a nightclub, earning the title of compostable is getting into the VIP section. As long as you’re able to be broken down by microorganisms, they’ll let you in the front door, but to get past the velvet ropes, you have to be able to do it quickly and under ordinary composting conditions, and your end product has to be able to support the growth of plants. The bouncers are tougher in the VIP section too; they’ll make sure you have all the right IDs before they’ll let you in. When a product is actually certified compostable, it will have the BPI, ASTM, or EN Certification Marks on it, indicating that it has met ASTM and other standards. This ensures that the product has undergone that third-party testing and been approved by independent analysis. Manufacturers use BPI as well as other world recognized certification requirements to guide their choices of ingredients and make certain that their product will be able to be diverted to composting facilities along with food scraps and yard waste at the end of its life.

When you’re making the decision to switch to sustainable products and do your part to help the environment, it is important to be informed about the many choices you have. Knowing the difference between things labelled “biodegradable” and those that are certified compostable allows you to make the right choice for the goal you are hoping to achieve. A big indicator of whether a product is only biodegradable and not certified compostable is price. Certified compostables are not made from traditional plastics, and the completely different process used to produce the product makes them more expensive. If the price is too good to be true or significantly cheaper than other compostables you have seen, most likely you have found a “greenwashed” biodegradable product that is not certified compostable. 

If you’re hoping for perfect eyesight or that orange glow you can only get from carrots, you must choose the right vegetable. Only carrots will do. That is the same when choosing an alternative that truly is better for the environment and lives up to its claim. You won’t go wrong by choosing certified compostables or eating more veggies. Either way, Mama will be proud.