In theory, bags labelled as 'compostable' are made from vegetable matter like potato or corn starch which fully break down. However, the conditions have to be right for them to break down and often it isn't hot enough in a home compost situation. It might need centralised composting facilities where the compost is guaranteed to reach high temperatures.
If a bag is labelled as 'home compostable' and it has been approved as compostable by the Composting Association in the UK it should bear the seedling logo.
Some retailers are heralding the use of compostable packaging as a solution to landfill problems.
However, sceptics argue that most compostable packaging will be put in the normal waste for disposal in a landfill, with the result that, as with any other organic matter in a landfill, as it degrades it will give off methane.
And, if compostable packaging is put into the recycling stream, it can contaminate all the other materials, meaning that the whole batch cannot be recycled.
A key worry about the use of compostable packaging is that it promotes recycling, rather than reducing the amount of waste produced in the first place. It is always better to reduce and reuse than to recycle.
Waitrose has replaced its plastic fruit and veg bags with home compostable ones whilst it is getting rid of its 5p plastic carrier bags. Co-op carrier bags are home compostable.
Emma Priestland, a plastics campaigner at Friends of the Earth, said: “It’s good to see big companies like Waitrose looking for ways to reduce the plastic in their stores. But compostable, bio-based bags aren’t necessarily the gold-star solution they first appear. This is a case of swapping one kind of single-use plastic for another, when actually removing the packaging entirely would be the best option."