You may have heard that compostable bags are made from plant starch.
But are they made entirely from plant starch? No, plant starch accounts for only about 20-30% of the material; the most important ingredient is modified plastic PBAT.
What is PBAT, and is it plastic?
PBAT is not traditional plastic; it is derived from petroleum and undergoes chemical transformation of its molecules into resinous substances.
The new question is: what is resinous material?
Resins, similar to soap or cooking oil that congeals into a paste, are soluble and easy to break down.
Can we dispose of compostable bags?
Generally, the film used to make these bags is categorized into industrial grade and household grade.
For household use, such as shopping bags in malls or supermarkets, clothing packaging, gifts, and other items packed with compostable bags, they are usually suitable for home composting.
Manufacturers need to obtain certification for home compostability before producing these bags, marked with the "Home Compost" authentication symbol. It's usually necessary to print this symbol on the bag or shopping bag to make it easily identifiable. If you see this symbol, you can compost these bags in a home compost bin.
Only a very small number of industrial packaging items need to meet the conditions for industrial composting. These bags will be marked with the symbol "Industrial Compost" and should not be composted in a home compost bin. They require disposal with garden or food waste, taken to an industrial composting facility for processing.
In summary, it's simple—just look for the symbol. If the bags don’t have a printed symbol, it depends on their intended use.
All the types of packaging mentioned above can be composted at home.
How long does it take to compost?
The bags meet the standards and have certificates such as EN 13432 and ASTM D 6400. They begin to decompose after 12 weeks in a composting environment, provided the conditions are suitable. They can completely decompose into water and soil within six months.