Biodegradable vs Compostable plastics
There is a lot of confusion around using the terms biodegradable and compostable. Often they are misunderstood and used interchangeably, however; let’s break it all down so you can dispose with peace of mind.
Let's start with getting to know degradable and biodegradable.
Degradable is a term that refers to something “breaking down”. This is usually referred to without any timeframe of how long this something takes to breakdown… although often it’s microplastics that will eventually end up in the ecosystem, our food chain and us, and more often than not, it’s over a long period of time.
Due to the growing issues of plastic pollution, biodegradable plastics have increased in circulation for the last couple of decades. The term biodegradable means that the plastic can be broken down completely into water, carbon dioxide and biomass or compost. Great, huh? Nope. Sometimes, plastic isn’t so fantastic.
Let’s take a squiz at this a little more closely.
For plastic to break down in a reasonable time frame (months instead of years), the plastic needs to be exposed to the right bacteria and the right conditions (usually heat).
Bioplastics Australia has recommended that biodegradable products should feature a clear recommendation regarding the suitable end-of-life option and correct disposal for this product.
Not all biodegradable products are compostable. Bio-based products may not be compostable due to alterations and additives during the manufacturing process.
The label biodegradable means the product can’t just break down into smaller pieces of plastic but doesn’t dictate anything about not leaching chemicals into the environment or specify how long it will take to break down in imperfect conditions.
Landfills are generally horrible conditions for biodegradation and can cause the production of methane gas during the degradation process, causing way more pollution than carbon dioxide.
The very term “biodegradable” is so confusing that it leads people to assume it still biodegrades regardless of how it’s disposed of.
Now Let’s talk about the compostable.
All compostable packaging is also biodegradable. But the reverse is not true.
Composting is a way of controlling the rate of decomposition or biodegradation. Composting uses specific conditions to control moisture, temperature, and oxygenation to optimise microbial action.
This means that products that are biodegradable go from breaking down from 6 months - 1000 years to only 90 days in a compost.
The process of composting must not harm but benefit the environment. This means it must be able to support plant life, leave no toxic residue and be consumable by worms.
Over the last decade, scientists have developed test methods that can verify whether something can fully biodegrade in a reasonable time frame without leaving any residue and also certification for products that meet these certain criteria and standards.
There are two voluntary Australian Standards for compostable packaging (AS 4736 and AS 5810). These outline four requirements that must be met to be classified as compostable:
• ecotoxicity
• fragmentation
• biodegradability
• compost quality
AS 4736-2006: The general standard of plastic being “suitable for composting and other microbial treatment”. These generally need to be exposed to the higher temperatures of an industrial composting facility. This is where our pods sit.
AS 5810-2010: Verification for plastics that are home compostable.
To make things simple, we should really be calling any plastic capable of safely biodegrading compostable. Labelling things as biodegradable is far too ambiguous to be helpful.