That’s a good question, thanks for asking……
An additive is mixed with the master batch during production that degrades the polythene. This can have several names, but they work in the same way. The additive firstly starts to degrade the polythene under the influence of heat and light; technically the process starts in the factory.
Due to the bags being stored in a dark box, and usually in colder storerooms, the process only continues in landfill i.e. in the soil. Once the polythene has been exposed to UV light, the degradation reaction is accelerated by heat in the soil.
This breaks the polythene down transforming it into a fine powder and then biological degradation takes place. The end products of bio-degradation will be carbon dioxide and water, with a very small residue of non-toxic inert mineral material.
Provided customers do not have unusually “heated” stock rooms storage should be all right for around three years. After this time there may be some discolouration of the bag. Once the bag is in landfill it will take somewhere between 18 and 24 months to degrade depending upon factors such as the heat, thickness of film etc.