[Article from Tara's Blue Book for the Mediterranean sea]
Stéphane Bruzaud, Laboratory of Materials Engineering of Brittany (LIMATB),
University of South Brittany
Are bioplastics a solution for the future? Can they replace petrochemical-based plastics?
The term “bioplastics” evokes two completely different notions, depending on whether one refers to its origin or its end-of-life.
A plastic qualifies as “bio-based” when at least a fraction of it comes from a renewable raw material of plant or animal origin. At present, the plastics industry is still dependent on fossil resources, since over 99% of plastics are petrochemical. This dependence on one resource can eventually lead to disastrous economic, ecological and political consequences — hence the need to find alternatives through the use of renewable resources.
As for their end-of-life, all organic materials are likely to be degraded over time by physical, chemical or biological means and reduced to simple molecules like water, carbon dioxide or methane. However, biodegradability is highly dependent on environmental factors such as temperature, humidity, oxygen and microbes. To be considered biodegradable, packaging must be ultimately bio-assimilated in the presence of water and oxygen via microorganisms in a time period defined by the European Standard EN 13432.
The development of new plastic materials from renewable and biodegradable sources is therefore a major challenge for the chemical industry. In fact, 299 million tons of plastic were produced worldwide in 2013, 40% of which was destined for the packaging market. These figures illustrate the very small part of the current bioplastics market (less than 1% of annual plastic production) and also the magnitude of its potential progression.
Some examples of bio-based and biodegradable plastics
Among plastics, both bio-based and biodegradable, there are two main families.
The first consists of polymers extracted directly from plant biomass (starch, cellulose, etc). The starch extracted from potatoes, corn or wheat can be converted into a thermoplastic material, using conventional plastic processing methods. Similarly, cellulose — the most abundant molecule on earth – can be used to manufacture transparent and flexible films that are barriers to moisture and oxygen.
The second family includes polyesters obtained mainly by biological fermentation (PHA) or by biomass polymerization (PLA). A wide range of PHAs is foreseeable, including both rigid thermoplastic and more elastic materials that would cover a huge number of potential applications. PLA is chemically obtained by fermentation of sugars extracted from various plants like maize and beets. Having mechanical properties similar to conventional plastics such as polypropylene or polyethylene terephthalate (PET), PLA is also “biocompatible”, thus expanding its application to biomedical and pharmaceutical fields, and also to the production of fibers for making clothes, fishing nets, etc.
The biomass of plants and animals is an almost infinite reservoir which can be used for the production of many products, and in particular bioplastics. The management of end-of-life bio-based products is also a crucial issue in limiting waste accumulation. Bioplastics are generally considered as an eco-friendly alternative to petrochemical plastics because of their production from renewable resources and their biodegradability. However, to better understand the environmental impact of this type of material it will be necessary to analyze the complete life cycle by rigorous and unbiased means. This will allow us to precisely quantify the environmental impacts generated by these products and processes throughout their life cycle.