The Plastic Problem #1: Biobased and Biodegradable Plastic

Alessia Andreotti
September 1st 2015

People involved into plastic matters predict that in the next thirty years the consumption of this particular and malleable material will go from the current 300-400 million tons to the double amount, at least. Plastic, or rather plastics were born from petroleum-derived polymers and had immediate success thanks to their mechanical and chemical properties and the low purchase cost.

Today we are aware of the fact that plastic waste has become a big worldwide problem. Huge floating islands of trash are plaguing the oceans, slowly hacking into the marine food chain and into the aquatic ecosystems. Even in the so-called advanced civilizations we just recently started to recycle plastic and looking for solutions, such as designing bugs that eat plastic, developing a system to clean up the oceans and breaking down plastics with soil bacteria.

In the last few years, the scientific research has developed different ways to limit this kind of environmental impact  producing biodegradable plastics: plastics derived from renewable vegetable materials, that in the right conditions decompose and convert to carbon dioxide and water by the action of living organisms (mainly bacteria and fungi). These innovative materials are generally considered environmentally friendly.

Many researchers, however, pointed out that if all the petroleum-based plastics were produced from vegetable materials we would need at least two completely farmed Earths to fulfill the request.

These biobased plastics are usually produced  starting from cellulose to get a molecule identical to the one derived from petroleum (e.g. polyethylene, polypropylene).

So, the molecules of biobased plastics and the ones of olefin plastics (petroleum-derived) are identical. The difference consists in the base material, which in both cases is non-renewable.

What is the contribution of biobased plastics to sustainability if they are - being identical to the olefin - non-biodegradable? Do we clear our conscience just because they derive from vegetable material? Also these plastics are inevitably bound to end up in the floating islands of trash mentioned above.

Regarding truly biodegradable plastics, applied research is asking whether or not these materials are really transformed into carbon dioxide and water when placed in natural environments, such as rivers, lakes and seas. The enzymatic degradation of plastic is the result of a group of microorganisms contained in large amounts in the environment where the plastic is located. In seas or rivers the biomass is lacking and not able to break down anything, if not in very long time - tens or hundreds of years.

Therefore , biodegradable plastics and biobased plastics (features that may not co-exist in the same product) don’t solve the problem of plastic waste and it doesn’t seem correct to define them sustainable.

What are then the actions to foster for an effective sustainability? A second article will try to point this important topic.

Image: Shutterstock

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