Compostable vs. Biodegradable… ugh

We live in a world filled with complicated plastics, which include plastics #1-7, bioplastics, degradable plastics, and compostable plastics.

When people ask me recycling questions about San Francisco’s programs, I sometimes get funny interpretations. “That is combustable, right?”, “Yes”, I say, “it’s compostable”, meaning, it is acceptable in San Francisco’s green compost collection bin.

Plastic manufacturers are trying to green plastic packaging and capitalize on greenwashing.  Consumers are still trying to grasp recycling basics and when you add biodegradable and compostable plastics to the mix, it just adds to the confusion.  I often field questions from our customers who inquire about different products and their recyclability. “Can I compost my wheat-based kitty litter?”, “How about my biodegradable diapers, if there is no poo?”, “My fork says biodegradable, can I put it in the green bin?”

The answer to all of these questions is “no”, they are not acceptable in the green compost bin.

New “green” products and plastics are the cause of much misinformation and confusion.  The sales pitches, acronyms and poor labeling are so overwhelming that consumers say “I just throw everything in the recycling bin.”  This is not what recycling companies want to hear. 

The following are some examples of terms and phrases used in the “green/bio” plastics industry.

  • Biocompostable
  • New generation of plastics
  • Made from corn
  • Taterware, Spudware or Greenware
  • Renewable raw materials
  • “Feels and look like plastics for the most part” 
  • ASTM D6400
  • Polylactic Acid (PLA)

Regardless of what the manufactures claim, let’s learn how to properly sort plastics into the correct recycling, compost or trash bins.

Compostable Plastics or items certified as ASTM D6400 compliant are “capable of undergoing biological decomposition in a compost site…” (I spared you the longer version from the American Society for Testing & Materials or ASTM).  Their definition of compostable ASTM D6400 compliant plastics goes on to say, for a plastic to be called “compostable”, they need to meet three criteria. They must:

  • Biodegrade
  • Disintegrate, and 
  • Have no eco-toxicity

In short there must be no toxic residue left after the material is composted, it should look like dirt.

Biodegradable plastics that do not meet ASTM D6400 standards usually contain some plant based/“bio” plastics or additives mixed with real plastics and are not compostable or recyclable in San Francisco’s recycling programs.  Yes biodegradable or bioplastics may be greener or contain less petroleum based plastics, but once you mix plant and petroleum plastic resins you can not separate them, recycle or compost them, they go to landfill (San Francisco’s black trash bin).  Biodegradable plastics are designed to break down into smaller pieces of plastic outside of a landfill; they never “go away”.  We already have enough smaller pieces of plastics in our oceans. Do we really need more?

I advocate for zero waste everyday and hope that everyone can begin to think in the same way.  When determining what type of plastic to purchase (recyclable, compostable or non-recyclable) or any type of disposables for that matter, remember the basics (reduce, reuse, and then recycle). Ask yourself:

  • Do you really need the disposable product? What alternatives exist?
  • Can the product be replaced with something durable or reusable?
  • What is the end use or recycling options for plastics?


In San Francisco and most communities that have a three bin system, sort your plastics as follows:

  • Biodegradable plastics = landfill or trash
  • Compostable = compost
  • Recyclable (non-compostable or non-biodegradable) = recycling

WASTE ZERO everyday.

15 Responses to “Compostable vs. Biodegradable… ugh

  • You make a very valid point that all these new technologies can be confusing. We should strive to understand that confusing doesn’t mean we should try to better understand them.

    There are three basic groups of green plastics; bioplastics, degradable plastics and biodegradable plastics.

    Bioplastics are plastics made from renewable plant material such as corn, potato, etc. They are also considered compostable, not in your back yard compost bin but in industrial compost facilities. Why? because they require an initial chemcial breakdown of the polymer from being exposed to high heat (140 degrees) for about 10 days. After this initial period then microbes can do the rest of the job.

    Degradable plastics are typically made using standard polymers but with an additive that will chemically react to environmental conditions such as oxygen or UV. This chemical reaction causes the polymer to weaken and evenutally break down into smaller pieces. The idea with these is that the pieces will eventually break down into pieces that microbes can then finish off.

    The third class is biodegradable plastics. These are also trypically made using standard polymers and add in organic additives (usually not plant material). This type of plastic does not react to any environmental conditions just like standard plastics do not. They maintain the same physical characteristics as the original polymer which means they can be fully recycled. But once placed into an environment with microbes, the organic material provides a method so that microbes break the entire polymer down.

    None of the above definitions by themselves makes a particular plastic green or “GOOD” for the environment (although some companies would like you to believe so). To asses the environmental aspect you would need to look at customary disposal methods.

    For plastics that can make it into a professional compost environment, we should be using bioplastics. This would be things like utensils, plates, and other food packaging. Since food and green waste is being diverted from landfills to compost facilities this makes a perfect fit. For those bioplastics which end up in landfills, they will last for hundreds of years just like regular plastics.

    For plastics such as bottles which are used for water, sode, juice, dairy, etc. Biodegradable plastics make good environmental since. The bottles can still be recycled (which is the preferred solution) and those billions of bottles which are not will now biodegrade naturally by microbes. When bioplastics are used for this application it becomes important to remove that plastic before recycling or it will destroy the batch of recycled material.

    In my view oxo-degradables and other degradable plastics are not a good environmental fit. There are some appliacation that may make some sense such as eliminating the visual problems of plastic but they do not fully address the biodegradation of the polymer and they will react with the environment which makes them not a good fit into the recycle stream.

    I hope this information helps. Our company was created as an environmental company to help solve the plastic pollution problem surounding bottles. We evaluated all plastic technologies and determined that for bottle applications biodegradable plastics has the best environmental benefit than all of the other technologies. Its hard not to want to choose one solution and then try to make it fit for everything but unfortunately from an environmental perspective it doesn’t work out that way.

    If you would like to learn more about this technology we have placed a lot of information on our website to help in the education process of green plastics.

    Max Clark

  • Great information. Thanks for making the distinction between compostable and biodegradable. Especially useful are your 3 criteria to qualify as compostable. I will tweet this post.

  • Very informative!!
    In recent times, the world is becoming cognizant about the hazardous effects of plastic bags on the environment.
    Also PLA has been used to line the inside of Paper Cups in place of the oil based lining more commonly used, create Green plastics Cups, Cutlery, Carrier Bags, Food Packaging and even Nappies.

  • Michael Wong
    10 years ago

    Taterware now has the “6400 Series”, which adheres to ASTM D6400 criteria for compostability. Are items from this line allowable in the compost?

  • Michael Wong
    10 years ago

    Also, World Centric’s cutlery claims to be certified under ASTM D6400 as well…

  • wastezerosf
    10 years ago

    Durable compostable cutlery has been a long time coming. Now there are several manufactures selling certified compostable cutlery that also carry the words BPI certified or compostable right on the cutlery. I would be wary of brands that do not say “Compostable” or their websites do not carry 3rd party certification. If their compostability is in question, a quick call or email to the company will generally get your doubts answered.

    San Francisco’s compost collection program only accepts certified bioplastics with the BPI compostable certification ( or certified ASTM D6400 standards. Some manufactures claim they are compostable or meet ASTM D6400 but do not have certification to verify it.

    Buyer beware. Do your homework before purchasing “compostable” products and before placing them in the compost collection bin. All compostable plastics must also be readily identifiable as compostable (i.e. green band/label or legible font on the product) to be acceptable in the S.F. compost collection program.

  • Great information. I am sure everyone has had this problem with compostable and biodegradable. I will tweet this post as well

  • This is a good article about the complexity and sometimes greenwashing around plastics and bioplastics:

  • That’s an all around amazing post!

  • wastezerosf
    9 years ago

    Check out this compelling story about kids saying no to disposables. If you are about to “go green” rememer the waste management hierarchy, Reduce, Reuse, Recycle, Rot.

  • Thanks for this blog post, and thanks also to Max Clark for the great follow up information. We have a nascent urban farm project, trying to turn gravel parking lots into productive farm land. One of the primary ways we are trying to achieve this is through composting.

    We are trying to figure out ways to divert food waste from nearby food vendors and whether we could incorporate “enviro plastics” into our composting operation, and this post gave some super useful information.


Trackbacks & Pings

Leave a Reply

Your email address will not be published. Required fields are marked *