Compostable and Biodegradable

What is the meaning of Biodegradable and Compostable?

Biodegradable and compostable are referring to a product breaking down into organic materials under particular environment. However, the term “biodegradable” is often misused and applied to a broad range of different materials. A biodegradable product may biodegrade in some environments and not in others in an unknown timeframe.  Therefore, “biodegradable” is misleading if the environment in which it biodegrades and the maximum biodegradation time are not specified.

“Compostable” means organic waste such as food decomposes naturally under oxygen and microbe-rich conditions.  There are industrial compost facilities and composting systems for the home (e.g. a compost bin or a worm farm).  Compostable packaging is made of sustainable materials and plant by-products,  like corn starch, that are eaten by microorganisms, worms and so, naturally decompose in microbe and oxygen-rich environments just like organic waste, but much faster than biodegradable option. Certified compostable products break down as if they were never there. Ultimately this generates carbon dioxide and water without leaving any harmful residues.  Not only this will not pollute the environment, but also helps fertilize plants and vegetation.

To be valid the claim of compostable must be backed up against a certification standard.  Importantly, all certified compostable packaging will biodegrade, and when mixed in compost contribute to soils, but not all biodegradable plastics will turn into compost. Therefore, a compostable product is always more preferable over a biodegradable product.

What is the difference between Biodegradable and Compostable?

Biodegradation is a chemical process in which materials are metabolised to CO2, water, and biomass with the help of microorganisms. The process of biodegradation depends on the conditions (e.g. location, temperature, humidity, presence of microorganisms, etc.) of the specific environment (industrial composting plant, garden compost, soil, water, etc.) and on the material or application itself. Consequently, the process and its outcome can vary considerably.

In order to be recovered by the means of organic recycling (composting) a material or product needs to be biodegradable. Compostability is a characteristic of a product, packaging or associated component that allows it to biodegrade under specific conditions (e.g. a certain temperature, timeframe, etc). These specific conditions are described in standards, such as the Australian Standard on Industrial Composting AS 4736-2006 and Home Composting AS 5810-2010, which means for an item to be called ‘compostable” in Australia, it must be certified to the Australian Standard. For this reason, we use the term compostable instead of biodegradable, since our products are certified compostable in the Australian Standard.

What is the AS 4736 and AS 5810 standard for compostable bioplastics?

If a plastic material claims to be biodegradable and compostable in Australia, it must comply with Australian standard on Industrial Composting AS 4736‐2006. This standard provides assessment criteria for plastic materials that are to be biodegraded in municipal and industrial aerobic composting facilities. This Australian standard is similar to the widely known European EN 13432 standard, but has an additional requirement of a worm test. In order to comply with the AS 4736‐2006, plastic materials need to meet the following requirements:

  • minimum of 90% biodegradation of plastic materials within 180 days in compost
  • minimum of 90% of plastic materials should disintegrate into less than 2mm pieces in compost within 12 weeks
  • no toxic effect of the resulting compost on plants and earthworms
  • hazardous substances such as heavy metals should not be present above the maximum allowed levels
  • plastic materials should contain more than 50% organic materials

It is important to understand that industrial compost facilities and home composting systems are very different.  Industrial composting facilities can process organic waste at high temperatures (50°C or higher).  This, however, cannot be replicated in the home, thus accelerating the rate at which the waste decomposes. Therefore, just because product has been certified for the Industrial Composting AS 4736-2006 standard, does not mean it will decompose in the same way in a home compost system!

Despite the difference between industrial and home composting systems, the core requirements for the certification remain the same.  The testing period