6 Things to Know About Compostable Plastic
May 29, 2019 Jane Alice Liu By Jane Alice Liu

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…

What I didn’t know was that these compostable bioplastics are only able to 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 6 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, which is usually derived from plants like corn and sugar beets.2

Unlike petro-based plastics, compostable PLA material do not produce any toxic material.

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, it has an invisible word in the label: “industrially compostable”.

Unless your straw and other compostable plastic is explicitly labelled for home composting, it’s actually only industrially compostable. Why? Because..

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

They 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 never reach high temperatures consistently.

And, because it’s been labelled as compostable plastic, it must leave absolutely no toxic residue,4,5 so 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 affect 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 and no 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 it in the trash bin! It just gets sent to the landfill (where it just sits and doesn’t actually 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’s always other compostable material that you can actually throw in your backyard (like wax-coated paper straws). You can always use edible utensils, or even bring your own utensils (like metal or bamboo straws) to use.

What do you think of compostable plastic utensils and straws? Do you have other options? Let us know below!

References

  1. Mallegni, et. al (2018) “Poly(lactic acid) (PLA) based tear resistant and biodegradable flexible films by blown film extrusion” Accessed 16 May 2019.
  2. “(Bio)Degradable polymers from renewable resources.” Polish Academy of Sciences Scientific Centre in Vienna. Accessed 16 May 2019.
  3. Song, et. al (2009) “Biodegradable and compostable alternatives to conventional plastics“ Accessed 16 May 2019.
  4. “CSN EN 14995.“ European Standards. Accessed 16 May 2019.
  5. “DIN EN 13432.“ European Standards. Accessed 16 May 2019.
  6. Narayan (2006). “Biobased and biodegradable polymer materials: rationale, drivers, and technology exemplars” Accessed 16 May 2019.
  7. Narayan (2006b) “Rationale, drivers, standards, and technology for biobased materials. In Renewable resources and renewable energy” Accessed 16 May 2019.
  8. Preto (2016) “To be, or not to be biodegradable///that is the question for the bio-based plastics”
  9. “The environmental impact of corn-based plastics.” Scientific American. Accessed 16 May 2019.
  10. "Options to improve the biodegradability requirements in the Packaging Directive.” DG Environment – European Commission. Accessed 16 May 2019.
  11. “PLA in the waste stream.” Fraunhofer. Accessed 16 May 2019.
  12. “Waste management and recovery options for bioplastics.” European Bioplastics. Accessed 16 May 2019.