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Compostable plastics: What are the problems with biodegradable plastics?

compostable plastics


A term that is often (and mistakenly) equated with the definition of "biodegradable" plastic. The only plastic that can decompose into CO2, and biomass without special conditions and in a short time can be called compostable.

Some types of biodegradable plastics are also capable of this, but they take an order of magnitude longer and still leave behind a chemical trace, so they cannot be considered compostable. This always means biodegradable, but not vice versa.

Bioplastic (biopolymers) is a general name for several types of industrial composting facility materials. It should be distinguished:

Bio-based polymers compostable plastics

For example, compostable material plastics are not always biodegradable, and compostable products made plastics are not always made from biomass.

Types of bioplastics

Type 1: Compostable (Biobased + Biodegradable)

Bioplastic (bio-based plastic) is made from biomass. Over time, under certain protocols, they decompose into natural elements: biomass, carbon dioxide, methane. This plastic can be composted.

bioplastics Pros and Cons

After the end of their service life, they can be recycled to obtain compost or biogas; agricultural areas and resources are required to grow raw materials;

Contribute to the elimination of fossil fuels food is used to make disposables when millions of people are hungry;

Decomposition is possible only under certain circumstances;

Must be collected separately from other types of plastics

bioplastics most common types of plastics and products

PLA = polylactic acid - polylactide. The most widespread and cheapest fully bio-based plastic to manufacture. Suitable for the manufacture of cases for items, as in terms of consumer properties, it is similar to PET. It can be used to make the lining of disposable cardboard cups and plates.

PHA = polyhyroxyalkanoate

PHB = polyhydroxybutyrate

Under composting conditions and in the natural environment. Their production costs are 5-10 times higher than those of conventional plastics.

Bio-PBS (A) = Polybutylene Succinate (Adipate)

Used for films, disposable bags, or cases for food and cosmetics.

Starch blends Rank

second among all bioplastics in terms of production. Can be used in a mixture with other bio-based product.

Biodegradable and oxo-degradable petroleum-based plastics

Biodegradable plastic is made from fossil fuels and is subject to accelerated environmental degradation due to its chemical formula. There are some composting facilities that use crude oil too. Using crude oil in petroleum-based plastics will enhance carbon dioxide related issues.

Although there are various laws relevant to petroleum-based manufacturing and composting facilities, but they are not universal rather each country comes with its own PLA regulations. The best solution against traditional plastics is to use biodegradable plastic bags.

It will not only prevent food waste but also encourage people to avoid using traditional plastics. So we can expect numerous environmental benefits.

Oxo-degradable plastics

There are also oxo-degradable plastics. They are not technically biodegradable. These are the types of plastic we are accustomed to, the accelerated destruction of which is achieved thanks to special additives that accelerate oxidation. The most popular additive is d2w (you can find its mention right on the packaging). Such plastic does not decompose but breaks down into smaller particles - microplastics.

Oxo-degradable plastics Pros & Cons

  • No must be collected separately from the general flow of plastic compostable materials
  • Cannot be processed into similar manufacturing
  • Break down into microplastics
  • Doesn't help reduce trash and pollute the oceans with less plastic
  • only applies to oxo-decomposable plastics

Oxo-degradable type of plastics and products

PBAT = Polybutylene adipate terephthalate Market

leader in biodegradable plastic products made, very durable, and flexible. It does not dissolve in water, which is why it is often used to cover the cardboard, such as disposable cups.

It is also used to make flexible films (including carrying bags and mulch) and is also included in medical cases.

PBS (A) = polybutylene succinate - polybutyl succinate

Can be made 100% from petroleum products or 100% from biomaterial. It is used for the manufacture of films, bags, packaging for food and cosmetics, agricultural films, and fertilizers with a delayed expiration date.

PCL = polycaprolactone - polyethylene glycol

It is not widely distributed on the market, it is used in medicine.

PVA = Polyvinyl Alcohol - polyvinyl alcohol (PVA)

Soluble in water, so it is used as a coating for dishwasher tablets and a coating for bait when fishing. It is oxygen-permeable and is often used as a liner in feminine hygiene items and diapers.

Type 3: Non-biodegradable plant-based plastics

Oxo-degradable Pros & Cons

  • Bio-PET, bio-PE, bio-PP are recyclable there is no commercially available 100% bio-PET packaging materials technology yet, but the Plant PET Tech Collaborative is working on it;
  • retain their properties for a long time in the environment
  • require additional agricultural areas for growing raw materials

Oxo-degradable Most common types of plastics and products

  1. Bio-PET, bio-polyethylene, bio-PP of them produce flexible packaging, bottles, bags.
  2. Bioplastics labeling

Biopolymers should have markings that will help you understand how to properly dispose of the material: compost, recycle or throw it into a regular waste bin. Trust only existing labels, not labels like "100% eco", "100% biodegradable", etc. Also, check the markings by the certificate code, sometimes they are used illegally.

The notion that these products are more natural because they are derived from plants is also false: in the production of plant growth alternatives, chemical additives can be used, similar to those used in the manufacture of plastics based on fossil fuels.

Compostable plastic is another confusing marketing term that indicates the suitability of a disposable item for composting.

Compostable plastic is designed to degrade completely (as opposed to breaking down into small pieces) under certain situations, which are found either in industrial composting installations or, less commonly, in-home composting systems.

But not all municipalities have industrial composting, and many cannot recycle compostable plastic packaging. This is why it is more likely to be buried or burned - just like regular biodegradable and compostable plastics.

What packages should I use?

Unfortunately, even reading a ton of reference material and understanding the recycling process for each type of compostable plastics will not help answer this question.

The fact is that bag manufacturers rarely indicate the composition of their products, and biodegradable bags are not accepted at waste collection points for recycling, because there is no suitable infrastructure for them.

The Complexity of Biodegradable Materials

Biodegradable Materials

The complexity of the disposal of all biodegradable materials is most clearly demonstrated by a study conducted by scientists from the University of Plymouth in the UK.

In this study, biodegradable, oxo-biodegradable, compostable, and plastic bags were placed in different environmental situations for three years: left out in the open, buried in the ground, submerged in liquid, and tested under controlled laboratory protocols.

In the open air, all the packages disintegrated into fragments after nine months, and with those that were submerged in soil, almost nothing happened. Only the compostable bag in the liquid completely dissolved in three months but remained in the soil for 27 months. Biodegradable and oxo-biodegradable bags retain their durability even after three years.

The experiment showed that none of the packets disappeared without a trace, no magical decomposition occurred - even the decomposed packets left behind particles.

How to degrade biodegradable items?

Biodegradable materials can only be degraded through industrial disposal. In the natural environment, this is important for the effect of microbes, oxygen, humidity, and other factors that cannot be reproduced in everyday life.

In countries without developed infrastructure to ensure proper disposal of biodegradable materials, the introduction of compostable and biodegradable bags can increase plastic pollution.

Is there a difference between biodegradable and compostable?

Composting is the process of breaking down organic waste by recycling it with microbes to create compost. Home compost is widely and successfully used to improve the quality and fertilization of the soil.

For the higher temperatures process to take place, the waste needs the right temperature, water, and oxygen. The organic waste heap contains millions of tiny bacteria that consume the waste by processing organic matter into compost.

Certification of compostable products. How is it going?

Biodegradability is the property of plastic to degrade during the lactic acid composting process.

The general government standard requires the following tests to determine the compostability of plastic packaging:

  • Testing for biodegradation;
  • Compostability single-use testing;
  • Testing for ecotoxicity;
  • Determination of the chemical composition.

The final processing of the test results leads to an unambiguous conclusion whether the given plastic packaging is compostable or not.

Compostable plastics are part of a closed system, where organic waste is stored in these plastics and is destined exclusively for industrial composting plants.

When these expensive compostable plastics end up in the environment, in landfills or dumps, they will not biodegrade in accordance with regulations and will remain as plastic pollution.

And if they end up in recycling, confused with ordinary plastics, they will destroy the entire batch of biodegradable and compostable plastics that would be recycled.

Compostable plastics Shocking Facts

Conventional plastics are usually made from petroleum. However, oil is a resource that is becoming scarce and therefore increasingly expensive.

Often it ends up initially even where it absolutely does not belong: in forests, on roads edges, or in the sea. That is why the manufacturing of compostable plastic has been used internationally for several decades, something that has been possible in research for 20 years.

And the industry standards for this have also existed since the 1990s. However, degradable plastics is available to consumers in all over the world not yet sufficiently accepted that the question arises why this is so.

Therefore it has not been possible to prove in any study that "oxo" degradable bags are really in the environment. Let it decompose without leaving any residue. This is why the term "oxo-degradable" is misleading because many people equate it with "bio".

The British Environment Ministry even denies the oxo-plastic any advantages. British experts even believe that it could harm the environment more than it would. Because it is still unclear what will happen to the plastics remains once they get into the ground and whether these remains could not even poison birds, fish or mammals.

Biodegradable types of material

Plastic bags with the label "Bioplastic" denote a type of plastic that is made from the renewable raw product. It has not yet been established whether this variety degrades like a plant. The "Plantbottle" that Coca Cola temporarily advertised consisted of corn and sugar beet. However, it decomposed just as badly as a conventional petroleum PET bottle.

Compostable types of material

Plastic declared as compostable can really break down into compost. However, this only works in special large-scale plants. As a result, compost plastic is sorted out and burned with conventional plastic.

So compostable plastic is good for the environment, right?

It is true that CO² is saved in the creation of bio-based plastics and also in their disposal. So our climate is less polluted.

And our finite oil reserves are also conserved.

However, bio-based plastics are not always biodegradable, don't forget.


This is where things get really interesting!

  1. Compostable plastic is only really compostable under the conditions of industrial/home composting plants. It has no business being on your compost heap.
  2. While compost is full of high-quality soil components, what comes out of composting bioplastics is worthless (CO² and water). Combustion is, therefore, the better alternative, because it creates at least reusable energy.
  3. For the cultivation of corn, sugar cane, and potatoes on a large scale, monocultures are created with all the ecological disadvantages. The soil is mostly overfertilized and oil is often required for cultivation, fertilization, and harvesting.
  4. The big cheating on compost is that some bio-based or biodegradable plastics say compostable, but that they are in fact not composted!

In search of these claims, various studies were held in the United States. The main purpose was to check the connection between greenhouse gas emissions, the speed of the waste stream, and its impact on relevant companies' economy.

According to the green guides, landfill sites started growing in numbers. Though some experts took these landfill sites as alternatives but this was not a perfect way to enhance greenhouse gasses' speed.

What is the market share of bio-based and compostable plastics?

According to estimates by industry experts, the global production capacity for bio-based and compostable plastics is around 2.27 million tons (European Bioplastics, 2018). For comparison: in 2016 335 million tons of conventional plastics were produced (Plastics Europe, 2017).

Europe accounts for approx. 11.6% of the generation of bio-based and compostable plastics, which corresponds to approx. 263,000 tons. These capacities have been increasing at a low level for several years. The market share varies depending on the industry.

Bio-based plastics

Can bio-based plastics be recycled?

It depends. There are bio-based plastics that have the same chemical structure as their fossil-based counterparts. Therefore, they can be recycled just like this one. One example is PET bottles with bio-based components, which are recycled together with conventional PET bottles.

Recycling in closed product cycles can lead to bottles with an average of 26% up to 100% recyclate. Regardless of the raw material source, high-quality recycling should take place as far as possible.


It is more difficult for bio-based plastics, which do not have the same chemical structure as fossil-based plastics. Many of them can be thermoformed, which is an important prerequisite for recycling. However, sorting systems, for example for light packaging from the yellow sack/bin, are not designed to sort these plastics. Exceptional plastics therefore mostly end up in energy recovery.

Generally, consumers tend to buy a product that does not involve them in the single-use of any item. They want to reuse products. It is the government that can ensure the single-use of low-quality plastics.