Canada – study looks at compatibility of biodegradable and traditional plastic bags

A recent study from Recyc-Quebec, entitled Evaluation of the Impact of Bidegradable Bags on the Recycling of Traditional Plastic Bags, shows that there are incompatibility problems with three of the four biodegradable bags reviewed in the study in terms of their recyclability with traditional plastic bags.



The study was funded by CPIA‘‘s Plastic Film Manufacturers Association of Canada (PFMAC), the Oxobiodegradables Products Institute (OPI), the City of Montreal and Recyc-Québec. It was undertaken by the Centre de recherche industrielle du Quèbec (CRIQ).



Overview



The study objective was to evaluate the potential impact of various biodegradable bags with the recycling of traditional plastic bags and on the quality of the recycled plastic. It was conducted in response to the growing interest in biodegradable bags and to the many such products that are slowly making their way to market.



Conventional bags used in the study were virgin high-density polyethylene (HDPE). Two types of oxo-biodegradable and two types of hydro-biodegradable bags were evaluated in the study. The oxo-biodegradable bags were "NeoSac" by the NeoSac Association and the Omniplast EPI additive bags. The hydro-biodegradable bags were "BioBag" manufactured by Polar Gruppen and "Eco Film" by Cortec Corporation.



Each of the biodegradable bags was mixed with conventional bags in proportions of five, 10, 25 and 50 per cent, using a high shear rate mixer kept under an inert atmosphere. Profiles of 0.25 x 0.50 inches were produced by extrusion; then films of thicknesses between 0.003 and 0.005 inches were blown from granules of the 16 mixtures and from granules of the conventional bags alone.



Measurements of bending and impact resistance were done on the extruded profiles. Measurements of tensile properties, flexibility and tear resistance were done on the films. The same tests were repeated on the profiles and films, following aging using heat, humidity and UV rays.



Conclusion



In summary, the testing showed that the hydro-biodegradable bags are not compatible with the traditional plastic bag recycling stream, primarily because of numerous problems presented during the preparation of the mixtures and extrusion of profiles and films. Additionally, the mixture of these bags with traditional ones induces an important drop in the mechanical performance of films, principally related to tear resistance.



Although the oxo-biodegradable bags showed excellent compatibility with traditional plastic bags during the preparation of mixtures and the extrusion of profiles and films, the films using "NeoSac" show rapid and considerable degradation after only a few days of accelerated aging. As a result, the "NeoSac" bags are not compatible with the traditional plastic bag recycling stream.



The EPI bags, however, can be considered as compatible with the traditional plastic bag recycling stream.



"Finally, this has also permitted the illumination that biodegradable bags do not all behave the same when they are mixed with traditional bags," states the study report. "The chemical nature of biodegradable bags (oxo and hydro) has a clearly significant influence on the final performance. Also, biodegradable bags of the same category likewise show significant differences, as it has been possible to show in comparing the performance of mixtures of NeoSac and EPI oxo-biodegradable bags with traditional bags following exposure to UV rays in a hot and humid atmosphere." As a result of the study conclusions, EPIC recommends that a certification process be established whereby a third-party certifies a biodegradable bag, if used as a shopping bag, for its compatibility with conventional recycling, where there is the possibility of mixing those bags with bags collected for recycling. EPIC also believes that a simplified v