Degradable, Photo-degradable, Bio-degradable, Compostable: What do these words mean?
Are you puzzled about what happens to a ‘plastic’ bag when you throw it away? You should be! The words to describe different kinds of bags are confusing, and can trick you into thinking you have found a ‘good’ alternative to the plastic bag.
Degradable
This is a confusing term because it is used in different ways. Degrade just means to break something down. You can degrade something by tearing it up into smaller and smaller pieces. So, most things are degradable. All of the processes below are forms of degradation. When it comes to degradable or 'photo' degradable plastic bags, what is left in the end are lots of small pieces of plastic.
EPI 'Degradable' bags are PLASTIC BAGS- They may have fully 'bio-degradable plastic additives', but these are just there to make the process of going from a plastic bag into a pile of tiny plastic pieces quicker. The benefit to these bags is that they don't hang around getting caught in trees and tangling up birds etc. for so long. But they do still contribute to the ever growing and forever remaining, pile of indigestible, polluting bits of plastic in the world!!!
This description is often used to make people think that they are using an environmentally friendly bag, they’re not!
Bio-degradable
Bio-degradable bags will break down from the action of naturally occurring micro-organisms, such as bacteria, fungi etc BUT bio-degradable material is not necessarily compostable, since what is left when the bag has totally bio-degraded may not be a safe and healthy addition to the soil.
For the bags to bio-degrade they need oxygen and moisture- the conditions have to be right for a bag to bio-degrade, if the conditions aren’t right the bag won’t bio-degrade well. Conditions are generally not right in your bin, landfill sites, the local river, at sea or up a tree. Typically it can take years for bio-degradation to occur in a landfill site, if it happens at all. So bio-degradable bags are not the answer to plastic bag litter.
Bio-degradable plastic is also bad news for recycling. It is not recommended to mix bio-degradable plastic with ‘normal’ plastic. If plastic recycling is contaminated with bio-degradable plastic, the subsequent product could be corrupted and weakened.
Compostable
Compostable bags are usually made from corn or potato starch, and will rot down completely, and relatively quickly, into the soil in a compost site; they turn into carbon-dioxide, water, and non-toxic raw materials. They create a safe and healthy contribution to the soil. But, these bags should be composted rather than landfilled. In a landfill site rubbish breaks down anaerobically (without oxygen), which produces methane, a much stronger greenhouse gas than carbon dioxide.
Compostable bags are a good idea in Bristol, particularly, as they can go in our brown food bins once they are not strong enough to reuse any more. To be accepted in Bristol’s food waste bins they must carry the looped seedling symbol.
Compostable bags must be certified as such and are labeled with the following: American standard ASTM #D6400-99 or the European standard EN-13432 or DIN V-54900.
For more information see: www.plasticbagfreehebdenbridge.co.uk