Biodegradability and the packaging industry

As market demand for environmentally friendly plastics grows, CSIRO is helping the packaging industry assess product biodegradability.

With the knowledge that ecological damage can be bad for business, many industries these days are looking for technology that embraces existing industrial processes while minimising their environmental impacts. Petroleum-based plastics that pollute land and water ecologies are a case in point. The fact that these polymers are indestructible adds a further cumulative debt to the environment. The response to date has been to replace, conserve or recycle plastic.

While these approaches are proving acceptable to consumers, CSIRO wants to push the envelope a step further by addressing the current core ecological limit: the lack of biodegradability in plastics.

Most petroleum-based plastics never fully decompose. Over time, photo-degradation breaks down plastic products into smaller pieces, but the polymers themselves cannot be decomposed by any known microorganisms. Meanwhile, the annual consumption of plastic shopping bags alone has been estimated to be more than 500 billion units, equivalent to 60 million barrels of oil in the manufacturing process.

In response to the scale of the problem and the complexity of natural decomposition processes, Dr Dong Yang Wu, from CSIRO Manufacturing and Materials Technology, has assembled 60 scientists into a multidisciplinary team whose key goal is to introduce sustainability to plastics. In addition to developing new materials, her Sustainable Polymeric Materials Group has established a biodegradation test facility to service researchers and industry.

"With pressure mounting, especially on the packaging industry, we need the ability to assess the biodegradability of plastic products — be they from renewable or non-renewable sources — and to do so against local and international standards," Dr Wu says. "This is an important issue if the plastics industry is to operate in markets that are becoming more willing to protect the environment."

With petroleum a limited resource and plastics posing a mounting disposal problem, there is a global trend towards bioplastics. However — surprisingly — even though bioplastics are biodegradable, the environmental impact problem still extends to these materials. "When you make bioplastics as strong as petroleum-based plastics, you turn off the biodegradability during the product's service life," Dr Wu says. "These products will eventually decompose but the timeframe required may be longer than desired."

At the new testing facility, industry can access the same techniques used in CSIRO's R&D work, with the tests clarifying how efficiently a product decomposes once it is tossed out. For the scientists, the facility is one aspect of a broader program that ultimately seeks to develop understanding of the biodegradation mechanisms, in order to design materials with superior performance and triggered biodegradability at the end of their service life.

"For the industry client, the data can provide a competitive edge, even helping them to export," says Dr Wu. "It allows them to know how their materials perform against their competitors and with regards to national standards. Additionally, if Australia wants to exploit its agricultural advantage and develop a manufacturing base for bioplastics using crop starch and waste fibres, then the availability of the testing facility can be integrated with new product development."

The tests provide information about the trade-off between the strength and biodegradability of plastics, the toxicity of breakdown compounds, the timeframe for decomposition, the ecological destination of the decomposed matter and the mechanism of biodegradation for different polymers and compositions. Some of these areas were usually neglected by industry, Dr Wu says, yet there is an emerging, ready-made market for materials with innovative performance traits.

The team draws on expertise from across CSIRO divisions to decipher the complexity of decomposition systems, and involves materials scientists, microbiologists, chemists, physicists and surface scientists.

Integral to decomposition processes are communities of microbes that use waste as food, and it is these tiny organisms that are the focus of microbiologists such as Dr Parveen Sangwan.

"The microbe community that decomposes waste — bacteria, fungi and other microorganisms — is subject to a lot of synergistic variables," Dr Sangwan says. "That's one source of complexity. The other issue is that 99% of microorganisms, especially bacteria, have never been cultured in laboratories and little is known about them."

In response, Dr Sangwan is applying molecular techniques to probe and identify microbes that initiate and propagate the biodegradation of different polymers.

"The strength of this approach is that we can produce information about the microbe's feeding activity as readily as we can determine which genes are being expressed, without distorting the behaviours with artificial culturing systems or oversimplifying the environmental variables that affect metabolic activities," he says.

The marriage with materials science occurs when knowledge about how microbes degrade waste builds a platform for designing plastic polymers with altered biodegradability traits that nonetheless perform well during a product's service life.

"We can't afford to be driven exclusively by commercial applications," Dr Wu says. "Part of our mission is to also build up capability for the future needs of the industry and advancement of science. So on one hand, the team is maximising the value of petroleum-based plastics through nanotechnology to deliver to industry more functions from fewer inputs, while creating less waste.

"The other part is to work on developing the next generation of plastics from renewable resources and build new technology platforms for society."