Compostable and Biodegradable are often used interchangeably, however the two concepts are very different technically.
Two key features are involved in making the distinction between the two terms: i) Time taken for something to completely decompose and ii) The impact of the decomposition of the material on the soil.
‘Biodegradable’ is used to describe any material which can be broken down by microorganisms over a period of time.
It is important to note here that the period of time is not defined and therefore can extend up to hundreds of years. Thus, when someone claims that it is okay to throw a banana peel on the ground because it is biodegradable, you can remind them that it takes two years for the peel to completely biodegrade, hence unless composted it can technically amount to littering.
Secondly, it is not necessary that post decomposition, every biodegradable material will have a positive or even neutral impact on the soil quality.
For instance, one popular variety of biopolymer is ‘oxo-biodegradable’ plastic. Oxo-biodegradable plastics are made from conventional plastics, with a small amount of additives added to promote its breakdown. Upon breaking down, the plastic only fragments into smaller pieces, and does not completely degrade. This process releases micro-plastics into soil systems, compromising soil fertility, regeneration, as well as food safety.
Further, when biodegradable matter does not decompose entirely and is not disposed off correctly, it can become a breeding ground for mosquitoes, cause the spread of diseases and also release methane, carbon dioxide and other greenhouse gases into the environment.
Compostable, on the other hand, has a time frame attached to the definition. For something to be called compostable, it must completely decompose in a soil environment in 180 days. Further, once decomposed, it should provide nutrition to the soil, a.k.a compost.
Even in the category of compostable there are two categories, industrially compostable and home compostable.
Industrially compostable substances require industrial facilities which simulate specific conditions using temperature, humidity etc. to completely get converted into compost. Whereas home compostable material can completely decompose into compost in 180 days in any soil environment.
Greenomers products are home compostable, meaning they do not need to be collected and processed in composting facilities, but naturally decompose into compost, water and CO2 when in contact with soil in 180 days.
This chart outlines the various levels of decomposition:
So the next time you are given a biodegradable straw, opt for a compostable one instead for the planet (and the turtles).