Current plastic bags take thousands of
years to break down and are made from
non-renewable resources.
Image: iStockphoto
Associate Professor Enzo Palombo fingers a plastic bag labelled as ‘degradable’: “… in 5000 years,” he quips, before shifting his focus to the slightly silkier texture of a true biodegradable plastic bag.
It’s all in the rustle – one of the only things that immediately distinguishes a biodegradable plastic bag from a regular plastic bag.
Biodegradable plastic bags are still a rarity and a long way from replacing the tough conventional plastic variety manufactured from non-renewable resources.
It is this toughness, or durability, that still makes conventional bags the norm and a worsening environmental headache. Plastic packaging accounts for up to 25 per cent of Australia’s municipal landfill.
Researchers at Swinburne University of Technology believe science might offer a solution.
The university is supporting two research projects investigating bioplastics: one into the use of ingredients from renewable sources, and another into the properties of biopolymers that determine their ‘compostability’.
The two projects have brought together Swinburne PhD students Suchetana Chattopadhyay and Cameron Way, who are examining the properties of bioplastics as part of their respective PhD studies.
The Director of Swinburne’s Environment and Biotechnology Centre, Associate Professor Palombo, is co-supervisor for both students and describes their work as among the most exciting applied projects he has encountered during his 20-year research career.
He says much of the excitement at the university has been generated by a composting machine (respirometer), which allows students to gauge how a project’s applications function in real time, over the course of an experiment.
Anchored to a bench at Swinburne’s Hawthorn campus with heavy chains, the jumble of glass jars and tubes that form the composting machine is used by Ms Chattopadhyay to test novel, chitin-based polymers.
Chitin is the world’s second-most abundant natural polymer and is mostly derived from shellfish waste, but also includes the exoskeletons of crustaceans, insects and spiders.
In collaboration with an industry partner, Ms Chattopadhyay has provided the first direct evidence of true biodegradability in novel, chitin-based polymers.
“Fungi from compost have grown on the chitin-based biopolymer, proving that this material is biodegradable,” she says.
Fungi plays a key role in degrading the most abundant biopolymers found in nature.
Ms Chattopadhyay’s objective to reduce inorganic landfill has the added aim of finding a biopolymer suitable for food packaging that is derived from raw materials that do not compete with food crops.
Up to now, the most common source of bioplastics has been starch from grains, but there is concern that food production is already under enough pressure from environmental stresses and the emergence of biofuels, without adding a new resource competitor.
External supervisor and the industry collaborator who developed the project’s bioplastic formula, Dr Myrna Nisperos from a specialty food business, says the research is driving the second generation of bioplastics, characterised by plastics biopolymers derived from non-food materials.
“Finding a biopolymer that is not derived from food production is especially significant in developing countries where people depend on starch as a staple food,” Dr Nisperos says.
“And we can prove that this second-generation bioplastics material will degrade in soil within six months or less, which means it can degrade anywhere in landfill conditions.”
Dr Nisperos says the project’s future direction and universal commercial potential are encouraging, with prototype biodegradable plastics possibly just months away.
In a parallel project, Swinburne student Cameron Way helped develop a sophisticated composting machine at CSIRO’s Materials Science and Engineering division in Clayton, Victoria, under the supervision of Dr Katherine Dean. Mr Way’s machine has allowed him to examine the composition, and mechanical and biodegradation relationships of polylactic acid (PLA)–lignocellulose biocomposites.
Since completing the new respirometer at CSIRO, Mr Way has been refining a technical balancing act between a biopolymer’s competing mechanical and biodegradability properties. In other words, ensuring the bioplastic is strong enough to be used in plastic packaging and then composts when discarded.
His research has led him to use a corn-starch-based biopolymer that is reinforced with lignocellulose fibres.Mr Way says the project exploring the properties of biopolymers since mid-2006 focused on the larger biodegradable plastics picture.
“Overall understanding of consequences for the future design of biodegradable plastics is frontier science which improves understanding to encourage more direct applications.
“An ideal balance of the competing mechanical and biodegradable properties in the biocomposite would involve improvements in both areas and finding a key bacteria or enzyme that kicks off biodegradability,” he says.
Mr Way says biodegradable plastics are essential to reducing the mounting dilemma of plastics waste: “The petrochemicals used to create plastic packaging will run out one day and we need to find alternatives that are sustainable.
“From an environmental perspective, both the PLA and wood fibres are 100 per cent sustainable, so they reduce the need to use crude oils and conventional plastics, and potentially eliminate long-term waste issues with landfill.
“With very strong uptake into the market and demand outstripping supply in the US, the best use for polylactic plastics is food and beverage packaging because it can be simply thrown into the compost,” he says.
Editor's Note: A story provided by Swinburne Magazine. This article is under copyright; permission must be sought from Swinburne Magazine to reproduce it.
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