Green Matter: Bio-based Plastics Stand Up to Sustainability Scrutiny

Plastics Today
04/27/2012

By: Karen Laird

A new study published in the Journal of Cleaner Production has, for the first time, attempted to make a qualitative evaluation of the general sustainability of the different bioplastics that are commercially available or soon to be on the market. The authors looked at environmental, health and safety impacts throughout the life cycles of these materials within the context of the 12 principles for sustainable biomaterials compiled by the Sustainable Biomaterials Collaborative (SBC), a coalition of organizations that advances the introduction and use of biobased products.

Entitled "Sustainability of bio-based plastics: general comparative analysis and recommendations for improvement", the study reviewed each type of bioplastic according to a variety of sustainability criteria derived from SBC's 12 principles. These criteria included the use of genetically modified organisms and hazardous pesticides to grow the crops used as feedstock, the use of hazardous chemicals during production and processing, the use of untested nanomaterials, potential workplace hazards, disposal options, disposal options and efficiency in the use of water, energy and materials.

The results are summarized in two Bioplastics Spectrums: the Bioplastics Spectrum for Occupational Health and the Bioplastics Spectrum for the Environment, which run from red ("Avoid") to green ("Preferred") and thus offer a quick visual comparative overview of the occupational health, safety and environmental impacts of the different materials.

From a health and safety perspective, the polyhydroxyalkanoates (PHAs), polylactic acid (PLA) and starch all came in on the green end of the spectrum. In the environmental analysis, starch, PLA, urethanes, PHA, zein and soy protein fell into this "preferred" category. By contrast, nano-biocomposites were on the "avoid" end of the scale in both analyses, mainly because so little is known about the health effects of nanoparticles - bio or otherwise - in (bio)composites. And, while none of the bioplastics could be considered fully sustainable, in the sense that they were 100% compliant with the criteria derived from SBC's 12 principles, the report cited sustainability improvements relative to petroleum-based plastics in aspects such as biodegradability, lower energy consumption and lower CO2 emission during production and compostability, for nearly all the bioplastics studied.

Steve Davies, director of communications and public affairs at PLA manufacturer NatureWorks LLC, hailed the report as comprehensive and supportive of the comparative overall sustainability of biopolymers. It comes as no surprise that none of the bioplastics commercially available today could be classified as fully sustainable. After all, as the report points out, "the development of bio-based plastics is still in its infancy", and obviously, there is room for improvement. "At NatureWorks, we've already implemented a lot of the recommendations listed in the report," he said. " In 2008 for example, we introduced fundamental new fermentation technology that significantly improved our eco-profile and carbon footprint."

In his opinion however, it looks as if the researchers relied on outdated sources. "And that has resulted in a number of unfortunate inaccuracies in their findings regarding the environmental, safety and health impacts of our Ingeo PLA production," he declared. He cites as examples, "the report states that an organotin-based catalyst system is used during the industrial manufacturing of PLA, and that 1-Octanol is used in the ring opening catalysis step. That is certainly not the case at NatureWorks".

And although he cannot comment on the catalyst system which NatureWorks uses instead - "I'm not in the position to disclose trade secrets"- he pointed out that third party certification offers a formal process for independently verifying that a product meets specific requirements or criteria. "We have recently received Cradle to Cradle silver certification for our entire Ingeo grade slate," said Davies. "and with the C-2-C process including an assessment of products for safety to human and environmental health, that's an achievement that counts for something."

All in all, the researchers have done an amazing job in sorting through the myriad issues relevant to the sustainability of bio-based plastics in their evaluation. And what emerges very clearly is the fact that no material or process is impact neutral. However, the bioplastics industry is striving to improve. As Davies says: "We will continue to better our performance. We are moving away from food crops, and our new plant in Thailand will be able to satisfy the demand for non-GMOs. We've improved our fermentation technology, and that has significantly reduced the amount of co-product - gypsum - produced."

According to the report, more research is needed to produce "novel environmentally friendly and safer plastics." Compared to the impacts of fossil carbon plastics, I'd say that today's bioplastics manufacturers are already pretty much on the right track.

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