"Compostable" Plastic Does it Fit in the Portland Metro Area?

New containers that look like plastics but are labeled “compostable” or “polylactic acid (PLA)” are appearing in delis, grocery stores, and fast food restaurants. As well-meaning businesses work to green their practices, many are turning to these new, usually corn-based, products.

It may initially appear that disposable containers made from corn instead of traditional natural gas or oil should have environmental benefits. When considering the use of any new “green” material, consumers must ask whether the environmental benefits are real. We must also weigh potential gains against new problems the material may cause. It is important to ask if such a switch saves or uses more natural resources and energy and whether it reduces or increases carbon emissions to curb climate change.

There is little evidence that the use of  corn-based plastics in place of petroleum-based plastics for take out or disposable containers is any more beneficial for the environment than any other disposable container.

Consider the following issues:

Landfill size: There is little relevant data that compostable labeled plastics will break down in a landfill. It takes air and water to decompose materials, neither of which is present in today’s contained landfills. Paper has proven to break down very slowly in the same environment.

Landfill decomposition increases greenhouse gas emissions: When compostable materials do break down in a landfill, they create methane, a more potent greenhouse gas than carbon dioxide. It is important to reduce materials that break down in a landfill–not increase them.

Consumer’s ability to compost plastic containers: Home compost does not reach necessary temperatures to break down corn plastic. And residential and business compost programs in the region do not accept the material. 

Corn plastics in a compost facility: Not all of the products labeled "compostable" have been tested for commercial grade facility composting. Some have been tested to successfully decompose in a compost facility; others have not successfully decomposed. Most of the facilities in our region are not equipped to take them.

Corn plastics value to compost: Biomass in compost comes from breaking down the cell walls of woody or food material. Polylactic acid is a simple sugar molecule that is digested quickly and provides little to almost zero mass to the compost.

Ocean plastics pollution: Oceans do not reach the temperatures necessary to break them down. Bioplastics will collect in oceans in the same way that other plastics do now.

Recycling issues: Corn plastics are not recyclable with regular plastics in our curbside or at the depots. Because they are difficult for consumers to distinguish from regular plastics, they can cause expensive problems for plastics recycling.

US dependence on petroleum: Corn-based plastics will not remove the need for petroleum to make the container. Corn production requires soil management machinery, fertilizers and pesticides, all of which are petroleum intensive.

Be a good consumer!

  • Watch for containers and bags labeled “compostable”, “biodegradable” or PLA. They often have the #7 on them.
  • Keep these containers out of the regular plastics recycling programs. Mixing the two materials together causes problems for petroleum plastics recycling.
  • Keep them out of compost containers as well. They are expensive for our local composters to fish out and throw away.
  • Opt out of all disposable containers. Bring your own durable coffee mug and water bottle, bring your own container to restaurants for take away and leftovers.
  • Purchase locally made foods or grow your own to avoid the need for packaging for transportation and storage.