ODOUR REDUCTION | INNOVATION


New research is showing the high level of contaminating odours that can be present in post-consumer PE waste. Mark Holmes looks at current initiatives and technical developments


Identifying and tackling odour contaminants


Due to global and national sustainability strategies, as well as changes in legislation, plastics recycling will increase significantly over the next decade. As a result there will be an expected rise of recycled materials used in the packaging sector in particular, where new markets and applications will be developed. This will place significantly higher demands on the sensory qualities of recycled polymers; odour being the most prominent of them. The Department of Sensory Analytics at the


Fraunhofer Institute for Process Engineering and Packaging (IVV) in Germany is leading research into odour reduction in plastics recycling. “Apart from optical and process-relevant proper- ties, the overall odour of recyclates is increasingly the main focus, because it limits their further use in consumer goods,” says Fraunhofer IVV’s Miriam Strangl. “After successfully tackling issues with PET, recent developments have been concentrated on


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polyolefin recycling. Polyolefins show different sorption and diffusion characteristics compared to PET. Therefore, contaminated polyolefin waste from mixed post-consumer collections presents a particular challenge to the circular economy because the materials produced by existing cleaning and recycling processes often do not meet the high quality standards of the industry. “In order to improve overall smell, it is necessary to understand the molecular structure and the physico-chemical properties of the odourants. Based on the chemical identity of the volatile organic compounds (VOCs) responsible for the overall odour of the recyclate, formation pathways and sources of the respective odourants can be determined. Effective avoidance strategies, odourant scrubbers and/or purification strategies can then be developed.” However, characterising the odourants responsi-


July/August 2018 | PLASTICS RECYCLING WORLD 15


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