Do bioplastics really work as a substitute for conventional plastics?

What are Bioplastics?

Bioplastics, which refer to plastics manufactured from plant sources, present a feasible alternative to petroleum-based, conventional plastics.

Status of Bioplastics

The bioplastics field is nascent. Currently, these are replacing only a small portion of conventional plastics.

The world uses about 300 million tons of plastics every year in diverse products. That’s a heck of a lot of plastics. As of 2016, less than 1% of this is bioplastics – from what I last estimated, it is only about 2.1 million tons of bioplastics in an ocean of 300 million tons of plastics.

So, a question arises: Can bioplastics really replace or substitute conventional plastics on a much larger scale?

This is an important question that can decide the extent to which bioplastics can play a role in solving the plastic pollution.

And the answer to the above question is:

Yes and no.

Why such an ambivalent answer? To explain this, you need to know a bit more about plastics.

A bit about plastics

There are all sorts of plastics.

Some are thin. Some others are hard and thick.

Some are flexible. Some are rigid.

There’s even a class of plastic called thermo plastic elastomer that can be said to be in between rubber and plastic – it has properties of both.

Some plastics have a very low melting point (Polycaprolactone is a biodegradable polyester with a melting point of around 60 °C). Other plastics are stable even at 200 deg C (a class of plastics called polyimides can easily withstand temperatures up to 300 °C).

Most plastics do not biodegrade, but hang on for perhaps a 1000 years. But not all. Yes, there are conventional, petro-based plastics that are biodegradable. Even more interesting, there are petro-based plastics that almost instantaneously dissolve in water.

You get the point – plastics are a diverse lot.

It is hence a no-brainer that it will be difficult to replace plastics with anything!

Bioplastics is trying. But will it be possible for bioplastics to come up with products exhibiting such a vast diversity of properties?

Well, it is not impossible, because, bioplastics can be made with significant diversity as well.

And now, a bit about bioplastics.

Bioplastics today are made from a variety of feedstock, using diverse processes.

Some bioplastics hence can be thin and flexible, similar to the thin flexible plastic films we use in packaging. These are also biodegradable – that is, they are converted into water, CO2 and some harmless substances when they are disposed to a composting environment.

Some other bioplastics, especially those made from vegetable oils such as castor oil, can replace high strength nylons and industrial polyurethane. These bioplastics are typically not biodegredable.

So, it does look as if bioplastics can take on plastics, don’t they?

Not so fast!

Even though bioplastics also present significant diversity in properties, the bioplastics technology is still in its initial stages of development. As a result, given the vast diversity of applications of conventional plastics, it is unlikely that now, or in the near future, every plastic can have a commercial equivalent from the bioplastic sector.

The qualifying word here is “commercial”. Technically, perhaps 90% (or even higher) plastics can have a bioplastic replacement even today, given the diverse plant based resins and the numerous blends of bioplastics attempted. But at what cost? In 2016, most bioplastic replacements for equivalent plastics cost 3-4 times that of the conventional plastic product. For instance, most PLA (poly lactic acid) based resins today sell at about $5/Kg for small-medium quantities, while their petrochemical equivalents (say polyethylene or polypropylene) sell at $1.5-2/Kg – something that makes bioplastics hardly appealing to the typical end user.

So, the summary is: Don’t wait with bated breath for bioplastics to take over conventional plastics anytime soon in the commercial sense, though functionally they are closing in on the properties.

What is more likely is that select categories and applications of plastics will start getting replaced by bioplastics to begin with. These will typically be segments where either governmental regulations and mandates force them to use bioplastics (even at a higher cost) or for premium segments where the extra cost of “going green” is acceptable, and sometimes even welcome, by the end user segment. An example of such a premium segment could be packaging for the organic foods segment, where the typical end user is a sustainability-minded individual or a group, willing to pay much higher prices for aspirational, rather than tangible, benefits.

As in any new technology/concepts, bioplastics will start dominating these niche segments in the beginning. With improvements in technology, and decrease in their costs, more mainstream categories of plastics will start being replaced.

I recall meeting a company that sold bioplastic containers cups made from PLA. The promoter, somewhat known to me, said I could have anything in the cup as long as it was not hot. I thought he was joking – he was not. The resin from which the cup was made was made from starch, and its melting point was not far above 50 deg C! Sure, there are bioplastics that can stand much higher temperatures, but they cost a neat pile.

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Do bioplastics really work as a substitute for conventional plastics? - Cleantech Guide

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