Breaking down bioplastics: The biodegradability conundrum

Iranpolymer/Baspar Only nine per cent of all plastic produced worldwide is ever successfully recycled, meaning most ends up in landfill. Therefore, the need to develop and rollout bioplastic alternatives that biodegrade in natural conditions is intensifying.

Here, Dr. Ashlee Jahnke, head of research and development at biodegradable biopolymer developer Teysha Technologies, explores the complexities of bioplastics, their environmental impacts and the pressing need for innovation in sustainable plastics.

Challenges with plastics and biodegradability

While most bioplastics are biodegradable, most do not do so in natural conditions. Instead, specific conditions are required, including high heat and humidity. Therefore, most bioplastics must be processed in industrial composting facilities to break them down.

Industrial composting facilities maintain controlled environments with specific conditions optimised for microbial activity and decomposition. In these facilities, organic waste, including food scraps, yard trimmings and compostable packaging, undergoes rapid decomposition due to high temperatures of 60 degrees Celsius, a humidity of up to 60 per cent and microbial activity. This includes specific microbial communities including fungi like Agaricus bisporus, Actinobacteria and Sordariomycetes.

However, not all bioplastics are suitable for industrial composting. Biodegradation requires the presence of specific enzymes, like hydrolase, lipase and oxidoreductase, and microorganisms, such as Sordariomycetes, that break down organic matter.

Some bioplastics, particularly those engineered for durability and stability such as bio-polyethylene terephthalate (PET), may not easily break down in these environments. Additionally, the lack of standardisation in composting facilities and regulations on acceptable materials further complicates the biodegradation process.

Furthermore, even if bioplastics are labelled as compostable or biodegradable, their degradation rates and end products may vary depending on factors such as thickness, composition and environmental conditions. Some bioplastics may require prolonged exposure to industrial composting conditions to fully break down, while others may only partially degrade or persist as microplastics in the environment.

As a result, the term biodegradable in the context of bioplastics should be approached with caution. While some bioplastics may biodegrade under specific conditions, including industrial composting as with polylactic acid (PLA), others may require alternative disposal methods such as landfilling based upon the plastic’s durability and potential for hydrolytic degradation.

Without proper infrastructure and standardised regulations for organic materials the environmental benefits of bioplastics may not be fully realised. As of 2024, the only regulations in place for bio-based plastics is that it’s organic carbon content must be clearly stated and calculated using CEN/TS 16137:2011. Instead, products labelled as bioplastic or bio-based plastic must truly adhere to sustainable principals and meet stringent standards. These standards would specify a minimum threshold for biodegradability and bio-based content that products must meet to qualify for the label.

Establishing clear definitions and criteria for what constitutes a bioplastic is essential. Through robust life cycle assessments, certification processes and labelling requirements, the integrity of bioplastic claims can be upheld.

Current bioplastics and their limitations

Many bioplastics, despite being derived from renewable resources, are engineered to be non-biodegradable and share similarities with conventional plastics in their manufacturing process.

The production of non-biodegradable bioplastics typically begins with the selection of renewable feedstocks, such as corn, sugarcane and cellulose. These feedstocks undergo processing to extract or convert the desired polymers, which are then polymerised using various methods, including condensation polymerisation or ring-opening polymerisation.

Bio-PET, derived from plant sources, is synthesised from monoethylene glycol and terephthalic acid, or its derivatives. With a composition similar to traditional PET — 70 per cent terephthalic acid and 30 per cent monoethylene glycol — it boasts comparable properties and is commonly used in bottles and packaging due to its durability. However, this durability renders it non-compostable, necessitating landfill disposal.

Similarly, PLA, derived from fermented glucose or sucrose, can be tailored for various applications by adjusting its L and D-lactide ratios. Increasing L-lactide enhances stiffness but also accelerates degradation. However, post-polymeric modifications will further increase stiffness while reducing the biodegradability, making PLA suitable for packaging, textiles and biomedical devices.

While bioplastics like PLA can be engineered to have varying degrees of biodegradability, others are designed to be non-biodegradable. They are manufactured using processes similar to those of traditional plastics, with renewable feedstocks serving as the starting materials. While these bioplastics offer advantages in terms of reduced reliance on fossil fuels and lower carbon footprint, their non-biodegradable nature poses challenges in terms of end-of-life disposal and environmental impact.


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