The Unspoken Truth: Compostable Plastics

If you've recently bought takeout from your favorite restaurant or fast food chain, you might have noticed some compostable cutlery, cups, and containers. These range from molded paper and wood chips, to seaweed, to bioresins, and even plain old plastics. What does it mean for this packaging to be "compostable?" As the US Environmental Protection Agency states*:

"In order for a plastic to be labeled as commercially 'compostable' it must able to be broken down by biological treatment at a commercial or industrial composting facility. Composting utilizes microorganisms, heat and humidity to yield carbon dioxide, water, inorganic compounds, and biomass that is similar in characteristic to the rest of the finished compost product. Decomposition of the plastic must occur at a rate similar to the other elements of the material being composted (within 6 months) and leave no toxic residue that would adversely impact the ability of the finished compost to support plant growth. ASTM Standards D6400 and D6868 outline the specifications that must be met in order to label a plastic as commercially 'compostable.'"

However, not all compostable packaging is equal. When we seek eco-friendly compostable packaging solutions, we must also look to the sources from which they are made and how they degrade after use. Here are a few sneaky biodegradable & compostable to look out for:

  1. Compostable petroleum plastics: PBAT (polybutylene adipate co-terephthalate) is a type of biodegradable plastic often used to make compostable shopping bags. Unlike other plastics such as polyethylene terephthalate (PET), PBAT can break down more easily due since it does not contain durable aromatic rings in its chemical structure**. Great news, right? Well...sort of. It's great news that PBAT breaks down easily instead of hanging out in our environment for centuries. However, what we overlook is the fact that PBAT is still made from common petrochemicals. Since a vast majority of these petrochemicals are made from unrenewable fossil fuels, PBAT only solves the latter half of the plastic sustainability issue. There are better alternatives which are both sourced from renewable sources and break down easily. 
  2. Plant-derived plastics: That brings us to plant-based plastics, which are exactly opposite from PBAT. Certain plant-based plastics have become popular such as sugarcane-derived PET. Packaging made of this PET acts just like conventional plastic--because it's identical! The only difference is that it's sourced from sugarcane, a plant source, instead of fossil fuels. This can be great for upstream sourcing sustainability, but doesn't solve the downstream pollution problem. Just like conventional PET, sugarcane PET takes about 450 years to decompose*** and beget harmful microplastics that end up in our foodstream^. In some ways, sugarcane PET plastic is even more problematic because it sounds sustainable and misleads consumers into thinking that the material is non-plastic. Again, we must find better alternative materials that are both sourced renewably and break down safely.

Not all compostable materials are equal, and biodegradable or plant-derived plastics are still contributing the plastic pollution problem. If you're looking for a truly eco-friendly compostable product, opt for materials like sustainably harvested paper, mushroom pulp, seaweed, and bioresins such as PLA (polylactic acid) & PHA (polyhydroxyalkanoate) that are made from plant stocks including corn, grasses, vegetable oils. In the bioresin sector, PHAs are even superior to PLAs because they are marine biodegradable^^ and are naturally occurring in ocean bacteria and PHA precursors are even found in the human body^^^'.

All the above options can replace plastic in many single-use and multiple-use packaging applications with the bonus of being made from renewable plant sources and degrading safely under compost conditions. Contact us anytime If you need a sustainably-sourced, industrially compostable packaging material. Our patent-pending blend of upcycled bamboo and various PHAs is designed expressly for consumer goods that must endure a years-long shelf life.

Be sure to look out for sneaky coatings or treatments, too. Although paper itself is both compostable and recyclable, many manufacturers coat the paper with a layer of plastic to render it waterproof. Mixed materials or laminates are usually impossible to recycle and often cannot be composted.

At the end of the day, compostable products are a great way to divert waste from landfills and composting is a growing industry. If we avoid the sneaky plastics above, many compostable products that end up as litter or are incorrectly disposed of in the landfill are still better for the environment than conventional plastics because they do not degrade into harmful microplastics. Be sure to sort your compostable products into the green or brown composting bin if you have access to one!

Citations: *, **American Chemical Society, ***Forge Recycling, ^, ^^Suzuki et al 2020, ^^^Takahashi et al 2017, 'Koller et al 2010.