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In response to a news release that OWS Organic Waste Systems (OWS) in Ghent, Belgium and the Institute of Polymer Technology, University Stuttgart (IPT) are planning a multi-client study on oxo-degradable plastics, the Australasian Bioplastics Association (ABA) has placed its position on record with PKN.

The ABA says claims for biodegradability made by proponents of oxo-degradable plastics are misleading and do not conform with global standards, and such claims are being disputed and challenged by the bioplastics industry both here and overseas. 

Bioplastics are a family of products that are biodegradable, biobased or both. 

Biodegradability can be confirmed by certification to various internationally recognised standards such as EN 13432, ASTM D6400, or in Australia, AS 4736-2006, where biodegradability in industrial composting facilities is desired. Biodegradability is not affected by the source of the raw material, so fossil-based raw materials can be biodegradable as can some renewable raw materials. These materials, once having passed the standards-required level of testing are certified compostable and therefore biodegradable. 

Biobased refers to renewable raw material content in the material or product. For example, biobased-polyethylene (Bio-PE) can be produced from sugar cane, but it is not biodegradable and certainly not compostable. This material is not designed to end its functional life in composting. 

In the global market today, there are many offerings of derivative plastics claiming to be biodegradable such as those termed by their proponents as oxo-degradable or oxo-biodegradable. These materials are not and probably never will be certified compostable according to the internationally recognised standards.

Biodegradation requires consumption by microorganisms, such as in industrial composting or home composting, but time, heat and other critical factors that affect the biodegradation and disintegration of the product or material, are measured against a performance standard [such as Australian Standard AS 4736-2006 (amendment 1, 2009), referred to above and Australian Standard AS 5810-2010 for products designed for home composting] with pass or fail criteria, as prescribed by the relevant standard. 

The science behind the argument 

According to the ABA, products that cannot claim conformance to such standards, but only to 'test methods' for example, such as the oxos, almost certainly do not and will not biodegrade in a composting facility in any desired time frame. 

President of the ABA, Rowan Williams, discussed the ongoing claims in the marketplaces around the world with Professor Ramani Narayan, of Michigan State University, Distinguished Professor, Department of Chemical Engineering and Materials Science in the United States and a world renowned expert in the field of bioplastics and plastics generally. 

Professor Narayan gave a very scientific and simple explanation of why certified compostable plastics undergo biodegradation whereas some that claim “biodegradability” are somewhat short of the mark. 

“Biodegradation is a measure of the ability of microorganisms present in the target disposal environment to utilise/assimilate the test carbon substrate. Basic biology teaches how to measure the rate and extent of this microbial utilisation, and forms the basis for all the ASTM, ISO, Australian (AS) and European standards (EN) for measuring biodegradability (irrespective of what the initial degradation is – oxo, hydro, chemo or abiotic),” Prof Narayan says. 

“Under aerobic conditions, the carbon is biologically oxidised inside the cell to carbon dioxide (CO2), releasing energy that is harnessed by the microorganisms for their life processes. Under anaerobic conditions, CO2 + methane (CH4) (biogas) are produced.

“Terms such as ‘oxo’, ‘hydro’, ‘chemo’ and ‘photo’ describe potential abiotic (non-biological process) mechanisms of degradation. They do not constitute or represent ‘biodegradability’ − the biological process by which microorganisms present in the disposal environment assimilate/utilise carbon substrates as food for their life processes. 

“Because it is an end of life option, and harnesses microorganisms present in the selected disposal environment, one must clearly identify the ‘disposal environment’ when discussing or reporting the biodegradability of a product, e.g., biodegradability in a composting environment (compostable plastic), biodegradability in a soil environment, biodegradability under anaerobic conditions (in an anaerobic digester environment or even a landfill environment) or biodegradability in a marine environment.

“Reporting the time to complete biodegradation or more specifically the time required for the complete microbial assimilation of the plastic, in the selected disposal environment, is an essential requirement − so stating that a plastic will eventually biodegrade based on data showing an initial 10−20% biodegradability is not acceptable and is misleading, especially since the percentage biodegradation levels off and reaches a plateau after the initial rate and level of biodegradation − drawing a dotted line extrapolation from the initial rate and value to 100% biodegradation is scientifically untenable.

“Specification standards with specific pass/fail criteria exist only for biodegradability in composting conditions − compostable plastics. There are a number of standard test methods for conducting, measuring and reporting biodegradability; however, they do not have pass/fail criteria associated with it. Therefore, an unqualified claim of biodegradability using a standard test method is misleading unless the biodegradability claim is qualified by the rate and extent of biodegradation in the test environment, and validated by an independent third-party laboratory using internationally adopted standard test methods. 

“Claims of degradable, partially biodegradable or eventually biodegradable are not acceptable, because it has been shown that these degraded fragments absorb toxins present in the environment, concentrating them and transporting them up the food chain.

“Therefore, verifiable scientifically valid evidence from an approved third-party laboratory is needed to document complete biodegradability in a defined disposal system, such as composting or anaerobic digestion, in a short time period using the specified international standards”. 

Many of Professor Narayan’s published articles and contributions are available via the ABA website. 

ABOUT THE ABA

The Australasian Bioplastics Association (ABA) is the peak industry body for the bioplastics industry in Australia and New Zealand. The association is incorporated as a not for profit in Victoria, and has been in existence since 2005.

The ABA represents members in the promotion of and advocacy for, member’s products and materials. The association works with government, composters, industry groups, NGOs, brand owners and retailers, amongst others, to further the understanding and appropriate use of bioplastics in many different applications.

Membership of the ABA covers raw material manufacturers, converters and distributors of bioplastic products and materials throughout Australia and New Zealand.

ABA members represent some of the world’s largest bioplastics producers.

 

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