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What do you know about biodegradable plastic bags?

Since 2018 in Italian supermarkets are used only biodegradable plastic bags. What does “biodegradable” mean? Are they really eco-friendly?

January the first, 2018, came into force the Italian law regarding the use of ultra-thin plastic bags. This law imposes supermarkets and greengrocers to provide only 0,015 mm thick, biodegradable, compostable and certified plastic bags. In 2018 bags must be composed by at least 40% renewable raw materials, but in the further years it has to be increased (50% in 2020 and 60% in 2021). By this law, the receipt has to specify the prize of the bag, which is the same of previous plastic bags, but it could be not indicated anywhere.

What are renewable raw materials?

By "renewable materials" we mean resources that can be manufactured or generated quickly enough to keep pace with how fast they are used up. Petroleum is not an exhaustible resource since it is consumed to a rate much superior to which take place of natural form. Wood, meat, solar energy, etc. are renewable because they can rapidly regenerate so they are not depletable, therefore the usage of renewable materials does not affect natural resources and future generations. Not all types of bioplastics are renewable: the ones that derives from peat are not.

What is the difference between biodegradable plastics and bioplastics?

Bio-based materials (for instance bioplastic) consist entirely or partially of substances that derived from living matter (biomass) and either occur naturally or are synthesized. Bioplastics are made with corn starch, wheat, tapioca, potatoes, potato starch or vegetable waste such as potato peel. They can contain also cellulose, polyhydroxyalkanoates and other substances (such as PHA, PHB, PHV, PHH). “Biodegradable” indicates materials that can be degraded in water, air or biomass by bacteria or fungi.

Some types of bioplastics are biodegradable (for example polylactic acid), but others are not (as bio-PET, sometimes used to replace traditional plastic for bottles). Moreover, also some fossil fuel-derived polymers can be biodegradable (for example Pbs, used to produce some types of packaging). The reason is that biodegradability depends on four factors: how long rubbish remain in a specific place, its environmental conditions, temperature and presence of oxygen and microorganisms.

Are biodegradable plastics really eco-friendly?

According to German Federal Environment Agency, biodegradable plastic does not provide more ecological benefits than traditional plastic.

First of all, natural resources used to produce plastic bags (corn starch, wheat, potatoes, etc.) come often from conventional agricultural systems: fields are abundantly fertilized and sometimes they use genetically modified seeds.

Secondly, biodegradable plastic bags often finish in wrong waste disposals, such as dry sites or landfills. Dryness inhibits biodegradation but if they end up in landfills the outcome is even worse: during degradation process this type of bags will release carbon dioxide and methane, that pollute rainwater and soil.

In conclusion, the famous marine biologist Richard Thompson studied biodegradable plastic bags decomposition in nature: Most of the bags after three years in different kind of soils were still intact and could even carry 5kg objects.

In response to Thompson study, Assobioplastica (Italian association of bioplastic producers) reminds the importance of correct disposal of all kind of rubbish, that biodegradable bags belong to organic waste and that if they end up in ocean will degrade in just three months.



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