In a press release published on March 31, 2020, the Fraunhofer Institute for Process Engineering and Packaging IVV announced the publication of a study investigating the odors of post-consumer shopping bags made of recycled low density polyethylene (LDPE) originating from varying collection systems. Combined analytical methods were used to detect more than 60 odorous substances and develop a strategy for avoiding the presence of odors in recycled materials. This research aims to support meeting targets set by the new EU Packaging and Packaging Waste Directive (FPF reported), which calls for secondary raw materials for high-quality consumer products to have no off-odors.
The majority of the odorants identified by the study were identified as typical metabolites of microorganisms with a cheese- or feces-like odors, including carboxylic acids as well as sulfur- and nitrogen-containing compounds. This identification allowed the researchers to pinpoint pathways for odors to enter the recycling process and end up in the recyclate. The results can be used to adapt collection and process parameters to reduce existing odorants and avoid the formation of new ones. Recyclate produced from material previously mixed with other household waste found to cause more intense odors in the final recyclate, with odors increasing in response to higher organic fractions. Separately collecting LDPE waste was found to significantly reduce odors along with washing the separately collected material at 60 degrees Celcius before recycling.
Frauenhofer IVV (March 31, 2020). “Reduced off-odor of plastic recyclates via separate collection of packaging waste.”
Karen Laird (April 1, 2020). “What IS that smell?”
Cabanes, A. et al. (January 24, 2020). “Odorant composition of post-consumer LDPE bags originating from different collection systems.” Waste Management (104).