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Biodegradable plastics: The solution to traditional plastic waste?

Updated: Apr 26, 2021

Over the last few years, you may have heard the term “biodegradable plastic” as the average consumer and other stakeholders within the supply chain become more environmentally aware of the packaging and goods they consume, and the environmental detriments associated with traditional plastic consumption. Thus began the development and use of biodegradable plastics and bioplastics, in the hope of building a more sustainable solution for goods and packaging. But are biodegradable plastics the solution to the problems of traditional plastic? Well, the short answer is no... but there are options to explore.

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Since the mid 1900s over nine billion tons of plastic has been produced worldwide and around 91% of this plastic remains unrecycled (1). Therefore, in response there has been a large interest into reducing the plastic deficit and since the early 70s, the alternative “bioplastic” was commercialised and over a million tons are produced each year worldwide (2).

The conceptual understanding of biodegradation is somewhat misunderstood as the common assumption is that “biodegradable” material will just degrade naturally or it can be easily recycled and that’s the end of the story. However, biodegradability isn’t as simple as you think.

What is Biodegradation?

A biodegradable product can be decomposed in idealistic environments (light, temperature, humidity etc.) by biological organisms (bacteria, fungi, invertebrates) in aerobic (in presence of oxygen) or anaerobic (lack of oxygen present) conditions (3).

The process of biodegradation is made up of phases of fragmentation and assimilation:

- Fragmentation is where biological organisms (commonly insects, earthworms etc.) decompose and breakdown (hydrolysis by extracellular enzymes) the material to be then biodegraded by microorganisms in the assimilation phase

- Microorganisms then attack the material (soluble intermediates) to produce water, carbon dioxide, methane and environmentally friendly biomass which adds nutritional value to soil.

Another common misunderstanding is the interchangeability of the terms “Bioplastic” and “Biodegradable plastics”. It is important to understand the differences as they each possess unique qualities.

Classifying different plastics

Firstly, all plastic is degradable in the sense that all can be broken so let’s clarify:

- Traditional Plastic: These plastics are synthetic are made from non-renewable petrochemicals and possess long hydrocarbon polymer chains which are extremely resilient to naturally breaking down – they can last for hundreds of years. The degraded plastic material does not always return to nature.

- Biodegradable Plastics: Like traditional plastics, these are synthetic plastics created from petrochemicals but with a difference – niche additives added during manufacturing process result in traditional plastics that can breakdown quicker in the presence of sunlight and heat (photodegradable plastics/ oxydegradable plastics). This process is significantly faster than traditional plastic breakdown.

- Bioplastics: Unlike the former, bioplastics are made from renewable, organic resources such as corn, grain, vegetable oil etc. However not all bioplastics are biodegradable. As mentioned above, biodegradability is the decomposition of plastic into biomass, and this is seen in a type of bioplastic known as “Compostable Plastics”. The degradation and decomposition of these plastics occurs in a range between weeks and months however, other bioplastics that do breakdown but not in the same time frame are considered “Durable Bioplastics”.

You would think it’s a good thing now that the new standard commercial practice is “Biodegradable” plastic products and packaging, right? Not so fast.

Is bioplastic necessarily biodegradable?

No! The biodegradation of materials is not based upon the source of the plastic (synthetic petrochemical polymer chain or bio-sourced biomass polymer chain) but rather on the chemical composition of the plastic. A bio-sourced plastic does not equate to being biodegradable and in contrast a traditional plastic can be biodegradable, and bioplastic can be non-biodegradable. In the case of polylactic acid (PLA) it is both; a bio-sourced plastic made from renewable resources (starch, sugar cane etc.) that is also biodegradable.

Are there standards for biodegradation?

Yes! For packaging there is an accepted European standard for packaging and packing waste in which there are requirements for biodegradation and composting:

– Composition: The regulation sets limits for volatile solids, heavy metals, and fluorine in the initial material.

– Biodegradability: The acceptable biodegradability threshold is at least 90% in total, or 90% of the maximum degradation of cellulose.

– Disintegration: The ability of the product to break into small fragments during composting. The threshold for refusal is when more than 10% of the initial material cannot pass through a 2 mm sieve.

– Final compost and ecotoxicity: the composted material must not be modified by the packaging added to it and must not harm to the environment. The standard requires ecotoxicity tests on the final compost with performance levels no less than 90% of the control compost.

Biodegradability and Plastics: The benefits

Bioplastics are not all that bad as their main benefit is cutting down on the world’s petrochemical consumption. This is key as fossil fuels are an unsustainable, unrenewable fuel source resulting in environmental, political and economic implications as dependence develops on the use of foreign oil.

In addition, bioplastics produce significantly less greenhouse emissions than traditional plastics as plants synthesised from bioplastics absorb the same carbon dioxide emitted hence, there are no net emissions of carbon dioxide. Current research shows that using renewable resources such as corn-starch in biodegradable plastic production, greenhouse emissions could be reduced up to 75%.

Compostable plastics are truly revolutionary as not only do they reduce greenhouse emissions, but they have added nutritional benefits to soil. The produced humus adds minerals key to soil growth and likewise the soil can absorb carbon dioxide further reducing emissions. Most governments have regulations in place for household compost to be sent to compost facilities which possess the ideal conditions for decomposition - a pure win for the environment.

Biodegradability and Plastics: The issues

As mentioned above, there are bioplastics are better than traditional plastics and more ‘eco-friendly’ but they are not the answer to the puzzle of long-term plastic sustainability.

Although biodegradable plastics and bioplastics are made from renewable natural agricultural products, a 2010 study from University of Pittsburgh concluded that the number of pesticides and fertilizers used to grow the raw materials for biodegradable plastics significantly offsets the plastic pollution they eliminate. Likewise, the extensive amounts of land are required to supply the current demands of plastic; this in turn would take away the space available for agriculture and crop production.

Moreover, not all bioplastics and other plastics cannot be grouped and degraded together as each release toxic metals and other traces in addition to greenhouse gases. If biodegradable plastics are incorporated into a batch of plastic recycling, it can ruin the batch, causing it to be sent to landfills.

Another significant issue with biodegradable plastics is their cost. Polylactic acid (PLA) is a biodegradable plastic that typically costs 20 to 50% more than comparable materials (4).

So what is the current state of affairs with plastic and where do we go from here?

Current and Future Plastic State

The current state of biodegradable and bioplastic use is that polyethylene terephthalate (PET) is the standard for packaging and consumer goods. PET is recyclable however it mostly serves a single-use purpose as it mostly cannot be recycled properly; this is due to its ease of contamination and recycling systems being inadequate to solve this. PET also poses a concern for human consumption as it known to leach antimony trioxide and phthalates and present health risks such as stunted growth, reproduction issues, low energy levels, body balance issues, and inability to process stress.

Whilst PET is the most recycled plastic worldwide and is the only plastic rated #1, the accumulation of waste, lack of degradation and other environmental detriments from manufacturing and logistics make PET highly unsustainable and not the answer to the plastic issue. Thus, companies are continuing to research and develop sustainable alternatives for consumer goods and packaging.

Biodegradable plastic alternatives and substitutes are a conundrum for large-scale commercial companies as these small changes have big business implications. For example, switching from bioplastic to glass packaging would reduce landfill sizes vastly as glass can be recycled and reused with much easier in comparison to bioplastic. However, the transportation of glass releases substantially more emissions as more fuel is needed to transport heavier glass due and, the overall costs increase significantly.

The future of plastics could be revolutionised with the shift from the linear economy to the plastic circular economy, where the key change is from single-use to multiple re-use. The way packaging is consumed is already changing as different industries are switching from PET to rPET, a much more sustainable as it can be 100% completely recycled: bottle, label, and cap. This means that RPET bottles have a lower carbon footprint than PET bottles, and it takes less energy to recycle and create an rPET bottle than to manufacture a PET one.

In the meantime, we’ll have to keep an eye on progress and do our best with what we have: reducing our reliance on petrochemical based plastics and bioplastics and searching for new better alternatives.


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