In the real world the
In the real world the temperature of the soil varies between 0 and 50°C depending on the location. The rate of molar-mass reduction and biodegradation can be extrapolated for any soil temperature by means of the Arrhenius relationship 3 . I have read many independent laboratory test reports on oxobiodegradable materials supplied by Symphony and by other manufacturers, which are entirely consistent with the published scientific literature 4 and with my own research. These manufacturers are not surprisingly unwilling to disclose their data to their competitors, but having seen the reports I am satisfied that if properly manufactured, oxo-biodegradable products will totally biodegrade in the presence of oxygen. I am aware of suggestions that fragments of plastic (whether oxobiodegradable, compostable, or normal plastic) attract toxins in a marine environment and are ingested by marine creatures. I am not however persuaded that fragments of plastic are any more likely to attract toxins than fragments of dead seaweed or any of the other trillions of fragments which are always present in the sea. I regard it as a positive factor that oxo-biodegradable plastics are made from naphtha - a by-product of oil, which used to be wasted. For so long as the world needs petroleum fuels and lubricants for engines it makes good environmental sense to use this by-product. I agree with the June 2009 report from Germany’s Institute for Energy and Environmental Research, which concluded that oil-based plastics, especially if recycled, have a better Life-cycle Analysis than compostable plastics. They added that “The current bags made from bioplastics have less favourable environmental impact profiles than the other materials examined” and that this is due to the process of raw-material production.” (see eg. www.bioplasticsmagazine. com/200906/1.pdf). Compostable plastics are designed to be deliberately destroyed in the composting process, but oxobiodegradable plastics can be reused many times and can be recycled if collected during their useful lifespan, which in the case of shopper-bags is about 18 months. Plastics of any kind should not be used for home-composting as they are often contaminated with meat and fish residues and temperatures may not rise high enough to kill the pathogens. Editor‘s note: This article is based on a counterstatement by Michael Stephen, Symphony Environmental in bM issue 03/2009 page 40, which included an offer by bM to contribute a scientifically based paper and to present data (e.g. ‘reports’ as required in section 7 of ASTM D6954-04). However, no data using the referenced standard was provided. The literature we received, is a list of publications that can be seen at www.bioplasticsmagazine.com/200906/3.pdf MT It is not desirable to send otherwise recoverable plastic to landfill, as plastic is a valuable resource. Nor is it desirable for anything to degrade in landfill unless the landfill is designed to collect the resulting gases, which most are not. However if oxo-biodegradables do end up in landfill, they are designed to disintegrate and partially biodegrade at or near the surface. Any particles deep in anaerobic landfill are minimal, and will remain inert indefinitely. They can never emit methane – unlike compostable plastics, paper, etc. So far as recycling is concerned, oxo-biodegradable plastic can be recycled in the same way as ordinary plastic (see www. bioplasticsmagazine.com/200906). By contrast, ‘compostable’ plastic cannot be recycled with ordinary plastic, and will ruin the recycling process if it gets into the waste stream. Please see www.bioplasticsmagazine.com/200906/3.pdf for a comprehensive list of Key scientific papers on the biodegradation of polyolefins. 30 bioplastics MAGAZINE [06/09] Vol. 4
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