Is compostable the same as recyclable?

According to Merriam-Webster,  recycling makes something new from something used before.  Most often, when thinking about recyclables, metals, plastics and glass spring to mind.

But using this broad definition, isn’t compostable the same as recyclable, too?

Something used before: wasted organics. Used to make something new: soil amendments. Generally speaking, the answer is “yes.”  But there are some exceptions.

Many “compostable” plastics can’t recycle — yet

One exception would be plastics stamped with the #7 PLA code.  This is the recycling code for biodegradable resins. But the #7 is a catch-all category that also includes non-compostable resins. Not very helpful to consumers trying to sort for recycling, is it?

Unless a #7 discard is also stamped “compostable,”  it may not be suitable for the composting bin.  Even then, many communities lack a local composting operation that can handle bio-plastics.

But #7 compostables aren’t appropriate for the traditional plastics bin, either.  When locales can’t separate compostable from traditional plastics,  all #7s go on the no-no list with stuff like styrofoam.

Compostable and biogradable aren’t the same, either

There are different ASTM standards for compostable (D6400) and biodegradable (D6868) plastics.  The two terms are not interchangeable in the world of recycling.

The U.S. Composting Council has published a primer on these types of plastics.  Review this compostability claims checklist if your company markets products in compostable packaging. It’s offered by the Plastics Industry Trade Association (SPI) Bioplastics Division.

Check with the local recycling coordinator for specific sorting requirements in your area.  Recycling compostable #7s requires a composting operation that will accept those resins.

If not, then #7 discards may not recycle as either plastics or organics. They will go to a landfill or incinerator.

Bioremediation may be reuse or recycling

Composting can do more than produce soil amendments.  When modified, it is a bioremediation technology for treating contaminated soil or water.

During treatment, the feeding activity of microbial populations degrade target compounds. They break the bonds of complex molecules, reducing the complexity of target compounds. Therefore, contaminants degrade into simple — and safe — compounds, like H20.

Then, the treated soil and/or water can be —

  • Excavated and remediated on-site and returned to the point of  extraction after treatment,
  • Treated in place (in-situ), or
  • Removed for off-site processing and beneficial reuse.

In the first two examples,  there isn’t a “something new” created from the old.   Because the treated soil or water is clean and reusable, it’s much like laundered clothes — it’s wear, wash, wear again.   Therefore, this is best described as reuse, not recycling.

Yet, treated soil might be mixed 50/50 with compost to make an engineered topsoil onsite. Then, one could make the case for recycling. A new product (manufactured topsoil) was made from the contaminated soil … even if used at the same site.

The same is true for off-site treatment. If the treated soil or water becomes an ingredient for another product, it’s recycled.


Blog – Is “biodegradable plastic” compostable plastic?

From the ASTM D20.95 subcommittee – active standards on recycled plastic