Bioplastics would seem to be a positive development in many ways. Rather than needing to have petroleum extracted and processed to supply the feedstock for making plastic, plant-based materials are used instead. However, a study by University of Pittsburgh researchers finds that plant-based plastics are not necessarily greener than petroleum-based ones.
To reach this conclusion, the researchers looked at several life-cycle factors. Factoring in side effects of farming needed to produce the feedstock needed to produce bioplastics, there are issues such as eutrophication of waterways, ozone depletion, and even carcinogens where some bioplastics fared poorly.
Twelve different plastics were evaluated in the study. In addition to the life cycle analysis, the plastics were also ranked according to green design principles. The production of some petroleum plastics had a better score than the bioplastics did. "Once in use, however, biopolymers bested traditional polymers for ecofriendliness." Polypropolene, for example, dropped from 1st place for production to 9th place as a sustainable material.
"Each polymer is also assessed for its adherence to green design principles using metrics generated specifically for this paper. Metrics include atom economy, mass from renewable sources, biodegradability, percent recycled, distance of furthest feedstock, price, life cycle health hazards and life cycle energy use. A decision matrix is used to generate single value metrics for each polymer evaluating either adherence to green design principles or life-cycle environmental impacts. Results from this study show a qualified positive correlation between adherence to green design principles and a reduction of the environmental impacts of production. The qualification results from a disparity between biopolymers and petroleum polymers. While biopolymers rank highly in terms of green design, they exhibit relatively large environmental impacts from production."
It should be pointed out that this study is based on current methods of production. So, while the bioplastics are not necessarily the greenest option at present, improved production practices could improve their relative ranking. Farming methods that reduce fertilizer use could help decrease the eutrophication scores, for example.
The results of this study should not necessarily be used to bash bioplastics or to make the contrarian argument that petroleum ought to continue to be used. Petroleum is, after all, a finite resource, and alternative stocks will eventually need to be embraced. Producers of both petroleum-based plastics and bioplastics could work with this study to identify the most damaging aspects of their methods in order to reduce their environmental impacts.
via: Building Green
written by renewable energy, December 04, 2010
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