Plastic fantastic

Arguably, the disposable nature of the plastic bag; more than any other consumer item; epitomises our throw-away culture. For decades we’ve treated thermoplastic packaging materials such as carrier bags as disposable commodities to be produced, consumed and thrown away in their billions.

In the UK alone, nearly 10 billion plastic carrier bags are distributed each year*; that’s about 400 per household. Consumers have come to rely on plastic bags, and it’s easy to see why. They are lightweight, strong and water-resistant, and it is these attractive properties which have secured their wide-spread use.

Breaking entrenched consumer habits has been at the heart of initiatives from the Government and private sector, which were aimed at limiting consumer reliance on the ‘single use’ carrier bag. A number of leading supermarkets voluntarily pledged to reduce their carrier bag distribution by 50%**, whilst other retailers charge for their plastic bags. Offering alternatives, such as the ‘bag for life’ has also become common practice.

Whilst such initiatives have raised public awareness and helped reduce the numbers of bags distributed, consumer attitudes in the UK and other Western economies have been slow to change. Meanwhile, this product of modern convenience poses a growing problem for authorities at both local and national level, with the bulk of waste plastics headed for municipal landfill at an unsustainable rate.

Long-term legacy

Most plastic bags, being petroleum-based, rely on costly, dwindling supplies of fossil fuels for their production, leaving both businesses and consumers vulnerable to fluctuations in the price of crude oil. If this wasn’t reason enough to reduce their usage, there’s the environmental impact of plastic waste to consider. Nature isn’t equipped to deal with synthetic plastics.

Although we can’t accurately estimate rates of decomposition – thermoplastics simply haven’t been around for long enough to be certain – most scientists agree it’s likely to be a very, very long time indeed, with 100-500 years commonly quoted. Although it’s obvious that the accumulation of petrochemical plastic waste in the environment cannot continue at its current rate, we continue to bury the problem.

In 2010, the decision by DEFRA not to enforce a landfill ban on items such as used plastics was met with relief by the plastics industry. According to the British Plastics Federation this is not due to a lack of will on the part of the industry, which it claims is keen to divert used plastics from landfill, but because the UK’s recycling and energy from waste capacity simply cannot keep pace with demand.

With no large-scale alternatives to landfill on offer, there is increasing pressure on the scientific community to provide a solution. One area of exploration is the potential to alter the composition of thermoplastic to hasten the decomposition of thermoplastic waste. A University of Wolverhampton team headed by Dr Iza Radecka has been looking at this in detail, and in particular, the potential for developing a natural, renewable and biocompatible bioplastic from bacteria.

A bug in every bag

Bugs could be the answer. For some time, professionals working in the polymer field have been aware of the potential of bacteria known to produce poly-hydroxyalkanoates (PHA) for the manufacture of biodegradable plastics. Iza’s own research specialises in PHAs as a replacement for many of the non-biodegradable petrochemical derived plastics currently in use.

Although the initial cost attached to the production of these bioplastics has caused them to be neglected, growing environmental concerns have injected new urgency into research, as Iza explains:

"There has been increased interest amongst the research community to investigate the potential applications for PHAs. This research could render shopping bags and other packaging material more effectively biodegradable, helping reduce its negative environmental impact. Through our research, we also hope to fully realise the other extraordinary abilities of certain bacteria to synthesise commercially useful and important biomaterials."

Commercial applications

Bacterial bioplastic such as PHA can not only contribute to a solution for the disposal of manufactured plastics, their unique properties make them suitable for many other commercial uses. Because PHA is immunologically inert and is slowly degraded in animal or human tissue, this property can be exploited for the slow release of drugs in the body. Agricultural applications include encapsulation of seeds for increased shelf-life and improved germination rates, encapsulation of fertilizers for slow release, manufacture of biodegradable transparent plastic films for crop protection and biodegradable containers for hothouse facilities.

Commercially, this area is ripe for development and companies that do so stand to gain a competitive advantage in the marketplace. The International Symposium on BioPolymers 2010, in Stuttgart reported encouraging advances in PHA production:

"Currently, several companies in different parts of the world are expanding fermentation capacities for PHA production… The currently low oil price caused by the financial/economic crisis probably will increase again in near future. Therefore, development of sustainable alternatives to petrol-based polymer chemistry such as production of biopolymers or bio-based polymers will become economically feasible."

Iza, who attended the International Symposium, is excited about the potential commercial applications for bacterial bioplastics:

"There are still challenges in developing biodegradable, high performance bacterial plastics, however significant progress has been made in different labs around the world. Bioplastics are a rapid growth area; it is a very interesting time for research in this area."

Working within the Research Institute in Healthcare Science (RIHS), Iza is a member of the Food Biology, Medical Microbiology and Disinfection Research Group. To find out more about this and other research being carried out within RIHS, visit: www.wlv.ac.uk/rihs.

 

* Department for Environment, Food and Rural Affairs (DEFRA), 2008
** In December 2008, seven of Britain’s leading supermarkets pledged to cut the number of carrier bags distributed by the end of May 2009 by 50% (against 2006 levels).