Biodegradable plastics: A green promise or a complex environmental challenge?

The earliest plastics were modifications of natural materials. Animal horn, amber, shellac, and tortoiseshell were manipulated into various forms by heating to produce a mouldable material. In the 19th century, synthetic chemistry in the chemical, dye, paper, and textile industries led to the discovery of cellulose nitrate or celluloid. It was used for photographic negatives, billiard balls and even false teeth. Very quickly, the demand for mass-produced items made from this easily mouldable material at an affordable price drove the rapid growth of the plastics industry.

Cellulose acetate was even adopted by the movie industry for making film rolls. Bakelite was introduced into popular use in the 1920s for radios. The 20th century saw the invention of Styrofoam, PVC, acrylic, polyurethane, epoxy, cellophane, nylon, synthetic rubber and textile fibers.

Plastics became popular — they were just cheaper and more readily available, especially during World War II, when natural raw materials were difficult to obtain. The global plastic consumption grew from 5.5 million tonnes in the 1950s to 110 million tonnes in 2009. Currently, approximately 60 million plastic bottles in the world end up in a landfill, incinerator, or the oceans every day.

Relatively very little plastic in the world is recycled. The top reason for this is the consumer’s inconvenience in separating waste. However, another major reason is also that the recycling process is tedious and labour-intensive — various types of plastic with different chemical compositions first need to be sorted, separately shredded, purified of impurities, then melted and formed into pellets, which can be used to create other plastic products. Recycling plastics also needs infrastructure development of recycling processes and facilities - for instance, consumers throwing plastic waste into a recycling bin in no way guarantees it is actually going to be recycled, unless the logistics of recycling is in place. 

But most of all, mainstreaming the recycling or reusing of plastics needs a mass shift in behaviour amongst consumers. Successfully changing human behaviour at scale is often more challenging than scientific advancement, which is why scaling the production, affordability and consumption of biodegradable plastics might be easier. 

Biodegradable plastics, designed to break down into natural substances over time, currently represent a small fraction, about 1%, of the total global plastic production. These are plastics that can be broken down by microorganisms into substances such as carbon dioxide, water, and biomass. However, to determine if a plastic is truly biodegradable and under what conditions, it must be tested. Adherence to standards like EN13432 are indicators of biodegradability. Much of the biodegradable plastic in the market is uncertified.

Further, the production process of biodegradable plastics can often have a high environmental footprint. The nature of raw materials, the supply chain of its raw materials, waste, including heat generated during manufacturing, determine if the biodegradable plastic is indeed environmentally friendly. For instance, if the raw materials being used to manufacture a biodegradable plastic are being transported from halfway around the world, then the emissions or air pollution from the shipping, flights, and last-mile transport add up to harm the environment. Life cycle assessments of biodegradable plastics, even when certified for end-of-life degradation, are a necessity to ascertain their environmental footprint.

In fact, the ‘end of life’ of a biodegradable plastic can be polluting too. For instance, those that degrade with oxygen typically produce carbon dioxide, water, and biomass, while those that degrade without oxygen may result in methane production. It is also undesirable for the end of life of such plastics to yield microplastics, which are very small non-biodegradable plastic particles less than 5mm through mechanical degradation. Life Cycle Assessments that measure the footprint from ‘cradle to grave’ can determine the waste generated once biodegradable plastics degrade. 

We also tend to overlook that degradation of different biodegradable plastics occurs under various specific conditions, including exposure to air, moisture, and microbes. If a product is labelled biodegradable does not necessarily mean that its degradation will occur in natural conditions without assistance. 

While returning to the earliest forms of plastic by mainstreaming bioplastics might be easier than coercing humankind to 100% recycle, it also requires large doses of responsible behaviour on the part of biodegradable plastic manufacturers. Testing for biodegradability and life cycle environmental footprint must be carried out carefully to avoid unintended consequences and encourage the development of high-quality biodegradable materials. 

The author is the CEO of Sustain Labs Paris. 

The opinions expressed in this article are those of the author and do not purport to reflect the opinions or views of THE WEEK.