PLA starch bags are described as a compostable plastic.Which can be confusing as they are a very different product from conventional, oil-derived plastics. Many people dismiss the compostable claim despite them being certified compostable See plastics and introduction for more on this.
PLA plastic is made from plant-based materials such as corn starch. You can find about more about starch derived plastics here .
Once again they are compostable and certified as such.
Same, same but different?
PLA bags are almost but not quite the same as conventional plastic bags. However they share enough similarities to make them a very useful substitute and can be a great tool in your plastic free armoury.
They are not quite as strong as conventional plastic bags so are not good as carrier bags but they are water proof for a limited amount of time, ( eventually there is seepage), but you can certainly use them to carry fish or meat home.
They are compostable and despite what folks might say they can be composted in a garden compost bin. Read more about PLA and composting here
Biobags & Others
One example of PLA bags is sold by the company Biobags. Back in the early days they were amongst the first to sell in the U.K. They have very good credentials. Their bags are certified to BS N13432 standard and are manufactured sustainably at facilities certified to ISO 9001 and ISO 14001. BioBag is the world’s largest brand of certified biodegradable and compostable bags and films made from Mater-Bi®. Biobags are the bags used in Modbury the plastic free town.
These days many companies make and sell PLA bags and you can buy the from supermarkets.
NB do check you bag is certified compostable.
What is compostable? To be classed compostable, items must biodegrade within a certain time (around the rate at which paper biodegrades), and the resulting biomass must be free of toxins, able to sustain plant life and be used as an organic fertilizer or soil additive. For a man-made product to be sold as compostable, it has to meet certain standards. One such is the European Norm EN13432. You can find out more here.
What For & Which Size?
If you can get it, I find the 6 liter size best to take shopping. The 8 litre is obviously bin liner size, and eyebrows are raised when you ask to have your steak put in a bin liner..
PLA bags can be bought from most big supermarkets. Biobags and other PLA bags can be found in hundreds of online shops including Amazon & Ebay. Some suppliers are listed here.
Composting PLA Plastic At Home
While most agree that PLA plastic is indeed compostable, many say that it can only composted in large scale municipal schemes. As we don’t have many large scale municipal schemes this they say is a pointless advantage.I say the days of large scale municipal schemes is fast approaching as governments aim to divert biodegradable rubbish from landfill sites.
AND I have been composting my PLA plastic for years. We have used and composted a number PLA plastic products (including Biobags , Deli pots and disposable Cutlery)
It does take longer than other products and sometimes I have found shreds of it in my compost but I dig it into the soil where it quickly disappears.
Read more about compostable plastics here
And never forget that bio-degradable plastic bags do not biodegrade where as compostable plastic bags do compost. Not all bio-plastics (plant derived plastics) are compostable. Read more here.