Distinctions between biopolymers and bio-based polymers important (Media review).

Posted by Evan Beach at Nov 08, 2010 04:00 AM | Permalink

The origins of bio-based plastics need to be clarified in a Vancouver Business Journal article that highlights the use of the materials in industrial applications.

A recent story in the Vancouver Business Journal provides an overview of the challenges manufacturers face when trying to work with plastics that incorporate natural molecules – so-called bio-based plastics. Companies are exploring new ways to handle the raw materials and optimize the molding process.

The article draws attention to an important trend in the world of plastics and green chemistry, but could have been more precise in the language used when referring to the polymers involved. Polymers are large molecules made of smaller, repeating molecules that are chained together.

The reporter does a good job of explaining the difference between two major types of bio-based polymers: “biodegradable” and “compostable” polymers. The distinction can be important  when manufacturers or consumers choose an environmentally friendly disposal method for a particular material. International standards define a biodegradable polymer as one that breaks down into smaller fragments due to the action of bacteria and other microorganisms. To be “compostable,” a polymer must degrade completely into carbon dioxide, water, minerals and biomass; and it has to do this quickly without hurting the overall compost process.

He could have also clarified that biopolymers and bio-based polymers are different.  “Biopolymer” refers to polymers that occur in nature or are produced by biological action. Cellulose, starch, proteins and polyesters made by bacteria (known as PHAs) are examples of biopolymers.

Then there are the synthetic polymers – like polylactic acid (PLA). These materials usually biodegrade and are made from biological raw materials, but are prepared by chemical methods.  PLA is made up of small molecules found in nature, but the polymerization process is a human invention. Similarly, nitrocellulose, which was historically used in photographic film, is a chemically modified version of a natural material, but does not occur naturally. PLA and nitrocellulose would be more accurately referred to as “bio-based” or “bio-derived” polymers.

These distinctions may seem minute, but they help clarify for manufacturers, regulators and consumers to what extent a material is truly natural.