Plastic bags are made from crude oil, which is made into a hard or a soft material. Plastic bags have only existed for one generation. In this short time, their extreme convenience has made them widespread all aspects of life, making them the synonym of waste. However, their decomposition is a very long process; in fact, they never fully decompose in seawater.
Plastic bags can be classified into 3 main groups according to decomposition:
1. Polyethylene plastic bags
These are the most common plastic bags that are made from crude oil. Their decomposition takes 700 – 1000 years, and in unfavourable conditions they never decompose.
Plastic bags decompose into smaller pieces, emitting toxic compounds in the process. They also make deadly decoy food for fish, birds, and animals. For example, plastic bags have clogged the sewage drains in Bangladesh, resulting in a flood that killed thousands of people.
Although polyethylene plastic can be recycled, only an estimated 1 – 3% of this reaches the recycling process.
2. Plastic bags with an accelerated decomposition process
These plastic bags are often mistakenly called biodegradable plastic bags. In addition to polyethylene, these plastic bags contain molecules of vegetable origin. In favourable conditions, the plastic is colonized by bacteria. They eat the filler and thus, make several holes in the plastic, resulting in its decreased porosity, which, in turn, contributes to its further decomposition in various ways, including by bacteria.
There have been many disputes about the environmental sustainability of this type of plastic bags, because although the decomposition process is accelerated, the bags are sometimes never really destroyed. They only disintegrate into smaller pieces that are a burden for the environment and a threat to birds and animals. Through the food chain, plastic even makes its way onto our table. The organism of a modern human being contains about 100 synthetic chemical compounds that were not there 50 years ago.
This type of plastic bags is definitely unsuitable for organic waste containers and also not really appropriate for plastic waste containers, because they impair the entire recycling process.
3. 100% biodegradable plastic bags
These plastic bags are made of 100% bacterial degradable material, such as corn, coconut, or rice starch, soya protein, etc. However, this type of plastic bags is less resistant to wear and tear and also more expensive compared to polyethylene plastic bags. Nonetheless, they are 100% biodegradable in favourable conditions and the decomposition process only takes a short amount of time. However, their production costs increase the world market prices of food products. These plastic bags can be cumulated in compost heaps.