As of 2017, the world has produced 8,3 billion metric tons of plastic and this number is increasing fast. To put this into perspective, the weight equals 822 000 Eifel Towers. To make matters even worse we have only recycled 9% of all these plastics. One of the recent and supposed sustainable solutions is bio-degradable plastic packaging, let's see if it is.
First, it is important to define biodegradable; the European Chemicals Agency defines the biodegradation process as ‘the biologically mediated degradation or transformation of chemicals usually carried out by microorganisms. The European standard for biodegradable packaging is EN 13432. This standard requires the packaging to break down under industrial-scale composting conditions within 12 weeks and leave no more than 10% of the original material behind. This means it is allowed to leave behind 9% (!) of its original material.
The next questions that arise are, how do we measure whether a substance is bio-degradable and to what degree a substance is bio-degradable. A plastic bag will take 500 years to degrade but the plastic bag has only been around for 50 years; so how do scientist know this? To make these estimates scientists use a method called respirometry. This method asks scientist to place an object like an apple core in a container with soil and microorganisms. To start the process, aerating the mixture is necessary which means to supply oxygen to the mixture. Then after a few days, the microorganisms start to digest the sample little by little, this produces carbon dioxide. Then the CO2 levels are measured which give you an indicator of degradation.
If you would like to measure the degree to which a plastic bag is bio-degradable using this test you would come to a very simple conclusion, it does not. This is because most plastic bags are made out of polyethene (PE), which the microorganisms do not recognise as food. After all, it is not a natural substance but man-made. If plastic bags don’t biodegrade, what do they do? Plastic bags photodegrade. Photodegradation is a process where solar UV weakens the polymers that compose the plastic bag until it breaks down into tiny pieces called micro-plastics. These microplastics are a big problem because they are light and easily distributed into nature by the wind. This is how microplastics enter our food chain, by for example ending up in our oceans where the microplastics are eaten by plankton who are in turn eaten by the fish we eat. Our fish is not the only place where small plastic particles enter our body, research shows that there is an average of 1.9 microplastic fibres in 500ml of tap water in Europe.
According to the Plastic Soup Foundation, biodegradable plastic is made entirely from renewable resources. This means that it can be made from a wide variety of sources such as potato starch or sugar cane. It also means that they will decompose fast and with no side effect in nature just like paper. When looking at the aforementioned characteristics of these alternatives the only question we should be asking is why are we not using these everywhere and what is the catch?
The issue with biodegradable and compostable packaging is that even though it could potentially decompose naturally in nature, the truth is that this rarely happens. Why is this? The first issue is that most of the biodegradable/compostable materials are designed to be decomposed together with food waste in high temperature industrial composting conditions. However, the preferred way to decompose food is by using a technique called Anaerobic digestion (AD). This is a technique that allows processors to decompose all their materials and simultaneously collect methane (a greenhouse gas) which is a more sustainable form of gas when collected using AD. This does not happen in the landfills where biodegradable plastics mostly end up and are decomposed, here it is released into the air and consequently into the environment. Another by-product of AD is the very rich fertilizer that can be used in the agricultural sector and it does not pollute the air and water around the compost side. Unfortunately, biodegradable plastics rarely make it to be decomposed using AD. Then there is also the issue of quality biodegradable packaging, you have real biodegradable packaging that could decompose with minimal environmental impact but there is also the greenwashing type. These seem sustainable but do not decompose properly, leaving the consumer think they are contributing to the environment when in fact they are not.
Another issue with biodegradable plastics is that the resources needed to produce them are renewable and produced by the agriculture sector. Ironically this takes up a lot of farming land and if we were to use biodegradable plastics as an alternative, we would not have enough land. Even worse, we could see a rise in the price of basic nutrition products because the cost of land will increase drastically.
These are some of the scientific disadvantages of biodegradable plastics, but the consumption behaviour is what makes it least attractive. The fact that biodegradable packaging is mainly single-use, is another problem. It does not solve the problem of trash ending up in our nature. A good example of this is the recent use of personal protective equipment (PPE). It has been widely documented that there are tons of disposable facemasks and latex gloves to be found throughout nature worldwide. These, just like most biodegradable packaging will take years to decompose. For a plastic face mask, this can be up to 450 years for biodegradable plastic this could be up to 30 years. Waste management is another tricky aspect, due to the increase in biodegradable plastics, there has been an increase in virgin plastics at composting facilities. In turn, this means that most of the biodegradable plastics will still end up in landfills or the incineration oven.
To conclude, biodegradable plastics could help with some of the plastic pollution problems but is not a long term solution. To be a viable solution it would need to stop ending up in our oceans and land as trash, thus leaving microplastics behind. This, however, seems far away, history has shown that our current consumption behaviour consisting of a surplus of disposable (plastic) packaging and our inability to distribute our waste correctly. Luckily it is not all negative, companies like Novamont have been able to produce biodegradable bags that fully degrade in the ocean within 1 year without any byproduct. Again, this does not mean it is acceptable to litter them around.