6 Things to Know About Compostable Plastic

Compostable plastic utensils seem to be popping up everywhere these days. From compostable forks, knives, spoons and straws, it’s as if I'm in eco-friendly heaven! But there's a catch.

What I didn’t know was that these compostable bioplastics can only be broken down in an industrial composting facility. Meaning I can’t just throw it in any compost bin (a bit misleading, I know).

Here are six key things you should know about compostable plastic utensils and straws:

1. Compostable bioplastic utensils and straws are made of plant-based plastic.

Plastic has traditionally been made out of petrochemicals (aka oil).¹ But, compostable plastics are made of polylactic acid (PLA) material, usually derived from plants like corn and sugar beets.²
 

Editor's Note: While plant-based plastic might sound much more natural, it doesn't necessarily mean it is toxin-free. Some studies have shown that plant-based materials also contain toxic chemicals, just like conventional plastic. That said, bioplastics might be better regarding carbon footprint and help us achieve a more circular economy. But they can also compete with farmland for food crops... it's a complicated issue!

2. You can’t compost compostable plastic in your backyard.

If you thought you could throw away your compostable fork or straw in your personal compost, think again. Yes, it might be labelled compostable. But what the label really should say is “industrially compostable”.

Unless your straw and other compostable plastic is explicitly labelled for home composting, it’s actually only compostable in very specific industrial conditions.

3. Compostable plastic can only be broken down by microorganisms in a high-heat environment (over 50°C).³

Bioplastics are designed to be composted in industrial-grade or commercial composting facilities, where high temperatures can be consistently reached to break down the bioplastic. Traditional home compost piles don't reach high temperatures consistently.

And, because it’s been labelled as compostable plastic, it must leave absolutely no toxic residue,^4,5 only a centralized composting facility can ensure this requirement. Otherwise, if the compostable plastics are not broken down properly by these microorganisms, they can have potential environmental and health consequences.^6,7

4. Compostable does not equal biodegradable.⁸

It’s easy to confuse the two, but there’s actually a difference. The biggest differences? Time and toxic residue.

PLA breaks down into CO2 and water within 3 months—if done so in an industrial composting facility.⁹ Compostable plastics (under EU standard EN 13432) are only labelled as compostable under specific conditions like temperature, humidity level and time. Compostable plastics should never produce any toxic material that affects water, plants, soil or other living beings.

Biodegradable can also be degraded by microorganisms and enzymes in natural environmental conditions, converting plastic into CO2, methane, water and biomass.¹⁰ But unlike compostable plastic, there’s no set timeframe or legal requirement regarding toxic residue. So, it can take years (possibly even hundreds of years) to fully break down. And like traditional plastics, they could potentially leak toxic chemicals into the surrounding ecosystem.

5. Don’t throw your compostable plastic in the trash bin!

Because these utensils and straws require very specific conditions to compost, don’t just throw them in the trash bin! They will probably get sent to the landfill (where it just sits and doesn’t get composted). Though, unlike traditional plastics, compostable plastics won’t leach toxic chemicals into the environment.

6. Don’t throw your compostable plastic in plastic recycling!

Compostable plastics have a great recycling turnover, as the material can be reused multiple times without lowering the quality of the material. But if you throw compostable plastics in the plastic recycling, you can actually ruin the entire recycling process.¹¹

Compostable plastics are made of a different composition compared to traditional plastics. This can lead to more problems when trying to reuse the plastic material into something useful.

Instead, throw them in a specific bin for biowaste. It’s then collected separately and taken to an industrial composting facility.¹² Talk to your local officials to see if this option is available near you.

The bottom line

Compostable plastic is a great first initiative to lower the impact of plastic on the environment, especially as it can prevent toxic contamination. But, there are still some other effects and infrastructural changes to make.

Don’t forget that there are compostable materials that you can actually throw in your backyard (like wax-coated paper straws). You can also use edible utensils or even bring your own utensils (like metal or bamboo straws) to use.