Biodegradable, Compostable and Industrially Compostable - What are the differences?
Some materials can be biodegradable, compostable and industrially compostable. But other materials are biodegradable but not compostable. What's that all about? In this article we'll get to the bottom of the compost heap and explain the differences between biodegradable, compostable and industrial composting.
In a nutshell
Biodegradable means that a material can fall apart - degrade, through natural processes - bio. Compostable is the same process but in a human-made environment with the specific goal of making compost. Industrial composting is composting on a much larger scale in a highly controlled and regulated environment. Want details? Read on!
Biodegradable
Biodegradable means that it can be disintegrated by nature. Bacteria, fungi, sunlight, and other processes split up the product and turn it into smaller natural components. It’s in the word itself, bio means nature, degradable means able to break down. “Able to break down by natural processes”.
In reality basically everything is biodegradable. Plastic just takes a really long time to biodegrade, but it does fall apart, just very very slowly. But what does this process look like?
Let’s get technical
To explain the process of biodegrading we'll use the world's favorite plastic Polyethylene, or PE, as an example. Unfortunately, it is also one of the most stable plastics and is very 'non-biodegradable'. This is pretty complicated, so let’s break it down (pun intended).
Plastics consist of chains made of molecules bonded together. We call these chains polymers. Ethelyne is a hydrocarbon, made up of hydrogen (H) and carbon (C): C2H4. Just like water is H2O - two atoms of hydrogen joined to one atom of oxygen. This means that C2H4 is two atoms of carbon joined with 4 atoms of hydrogen, just like shown in formula A. Another way of writing this formula is H2C=CH2 because of the specific way it’s bonded.
Polyethylene (Merriam Webster):
A polymer of ethylene.
Any of various partially crystalline lightweight thermoplastics (CH2CH2)n that are resistant to chemicals and moisture, have good insulating properties, and are used especially in packaging and insulation.
Polyethylene is a chain of ethelynes - hence the poly. If we look at formula B we see the same formula of ethelyne, but with a ‘n’ behind it, meaning an undefined number of ethelynes linked together. Link anywhere from 2 to infinite ethelynes together and you get polyethelyne - plastic. Makes sense?
Let’s leave it there, before we get way to technical. All this is to say that biodegradable means that these bonds that are created are broken apart again. Releasing the hydrogen and carbon back into the wild. Bonding ethelyne together makes a bond stronger than the one between Frodo and Sam. This bond makes Polyethylene, like other synthetic plastics, basically non-biodegradable.
But you can see plastic bags falling apart though, if it’s not biodegradable then what is that all about? Different processes, most importantly the sun, do break down the plastic bags, but on a very small level, the atomic level, the bonds remain mostly in tact. We call these tiny, tiny plastics microplastics. In time, we’re talking about thousands of years, these last bonds will also break apart and finally the plastic will be degraded back into it’s original components.
Now, materials like wood and leaves fall apart very quickly. The building blocks break apart and rejoin the cycle. That’s why it’s so important to leave trees and leaves on the ground once they've fallen. Fungi and bacteria break them apart and the living trees and plants can use the nutrients again. It makes a great compost!
What about bio-plastics?
Bio-plastics are a relatively new product. The way they biodegrade or compost depends on the type of material used to create the plastic. It's too complicated to discuss in a short paragraph. So to avoid over-complicating this article we will explore the world of bio-plastics in a separate article. Stay tuned.
Talking about compost
The international definition of compost is: organic soil conditioner obtained by biodegradation of a mixture consisting principally of vegetable residues, occasionally with other organic material and having a limited mineral content
Composting refers to a process in which you are specifically breaking down materials into natural elements for use as compost. You create an environment, in your composter, that is favorable for the bacteria, fungi and other creatures like worms, to break down the things you throw in there. In worm composters you let worms eat and tear apart the things you feed them. Is there a difference between worms in the wild eating an apple in the forest and the worms eating an apple in your worm composter? No, the apple is biodegrading, the nutrients from the apple are rejoining the cycle. It’s just that we have control over the process and we call that composting.
Compostable, because it’s a human term, is a protected term. Products have to check a number of boxes to be able to be called compostable. The EU and the US both have strict rules in place as to what can be called compostable. Like the EU's European Standard EU 13432 “Requirements for packaging recoverable through composting and biodegradation". For more information on composting in the US click here.
