The Paradox Of Eco-Friendly Plastic

Over the past few years, “eco-plastics” have been gaining increasing popularity.  With certain biodegradable additives such as pro-oxidants and starch, these plastics could degrade within five years when provided with the appropriate microorganisms and setting. Although biodegradable plastics are potentially more sustainable than plastics, however, there are a few points to bear in mind when purchasing or using them.  

Biodegradable plastic only decompose when they are properly composted.


Firstly, biodegradable plastics only decompose when they are properly recycled and treated under the right temperature, humidity, chemical and microbial conditions. If they are left in the ocean, or disposed of with other plastics in a landfill, degradation is not possible.  Even organic waste such as apple peels will decompose much slower in a landfill as opposed to a composter. Hence, the recycling of biodegradable plastics relies heavily on local infrastructure.

In addition to this, robust evidence shows that some of these so-called degradable plastics, more specifically, oxo-biodegradable plastics, will only break down into smaller pieces rather than decomposing.  These smaller pieces will eventually become microplastics and, as mentioned in the “life cycle of plastics” page, can have a detrimental influence on the eco-system.  

Plastics must be compostable to truly decompose without leaving traces of plastic in the environment. Biodegradable and compostable materials are not exactly the same. Compostable materials produce useful products once they break down, providing nutrition to the soil or generating biogas. Only plastics that decompose with other compostable materials in a composting environment in a defined period of time, usually within six months, are considered compostable.

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Compostable plastics such as PLA and PHB can be properly composed when treated in industrial composters. Globally, the proportion of compostable plastics that finish their life cycle in qualified composters remain unknown, and so far, the large-scale facilities available in Hong Kong are not able to compost them. The degradability of these plastics greatly varies under the composting environment. Efficient composting of these plastics usually requires aerobic environments, while currently the Hong Kong Organic Resources Recovery Centre only uses an anaerobic organic waste digestion system.  It must also be noted that at the moment ORRC prohibits any packaging from entering the composting process, regardless of their compostability, since it’s difficult to differentiate them.

In summary, while eco-plastics are a potentially great innovation, one must bear in mind that any disposable product takes resources to produce and may not be recycled/degraded as efficiently as we hope. Although this may make you want to switch over to Tetra Paks or paper cups, it's more important to remember that they are not necessarily eco-friendly either. These items take resources to create and are made from mixed materials, which makes them difficult to recycle. Hence, the best option is to ditch disposable and choose reusables instead.  

Research by Sustainability Office Intern Bingo Xu 2018