Traditional plastics are made from crude oil, when disposed of improperly oil-based plastics take hundreds of years to break down, cause a threat to wildlife, are contributing to pollution on land and sea, are consumed by wildlife and bioaccumulate in our food sources and, as a result, us.
In a bid to rid ourselves of single-use oil-based plastics we are instead turning to single-use plant-based plastics or bio-plastics. These bio-plastics are a form of polyester produced from plant starch such as corn, cassava, sugarcane or sugar beet. One of the most-common bio-plastics is a type of polyester called polylactic acid (PLA). It is commonly used in the manufacture of medical implants as it gradually breaks down in the body to lactic acid within around 2 years. Increasingly, PLA is being used as a “compostable” packaging material in cups, bags, magazine wrappings, cutlery, sanitary products, nappies, clothing and microwavable trays. As well as reducing reliance on crude oil-based plastics, bio-plastics have seen a rise in popularity due to their perceived “greenness”.
PLA products are manufactured with a resin ID code of 7, although widely used these are often misunderstood, this symbol shows the material that an item is made from and makes no comment on its recyclability or otherwise.
The difficulty with PLA comes at the point of disposal. Many PLA products are included in kerbside recycling schemes which are usually mechanical in nature and this material does not lend itself to these processes causing issues in the reprocessing facility.
Many of the film or bag like items are marked as compostable and find their way into kerbside composting collections and home compost bins. Their inclusion in kerbside collections is problematic as they appear, to collection crews, to be plastic which is not accepted for composting.
Although often marketed as “compostable”, PLA is industrially compostable and as such in a home compost bin will not degrade as it doesn’t reach a high enough temperature to break down.
In order to be composted these would need to be included in a forced heat, composting environment such as an IVC (in-vessel composting) facility however, if such a plant has a front-end plastic / packaging removal system this material will be taken out because it is, and acts like, a plastic.
If disposed of improperly and becomes a pollutant in land or sea these bio-plastics are equally damaging as oil-based plastic. They act in the same way as oil-based plastic and degrade very slowly at ambient temperature with marine tests showing no degradation after 1 year in a marine environment.