Nudging proper recycling: An in-depth waste analysis


The study conducted by WART and a multi-disciplinary group of NUS students sought to better understand recycling behaviour, and develop solutions to improve the campus recycling programme


As part of the University’s push to create a greener and more sustainable campus, the Waste Minimisation and Recycling Taskforce (WART) under the NUS Sustainability Steering Committee partnered with a multi-disciplinary group of NUS students between January and March 2020, to conduct a study to uncover insights on the recycling behaviour of the NUS community, and examine the effectiveness of recycling bin ‘triggers’ in reducing the amount of non-recyclables in recycling bins.

Associate Director Mr Loo Deliang from the NUS Office of Estate Development, who co-designed the study with the students shared, “Even though recycling rate in NUS has risen from 17 to 25 per cent between 2016 and 2019, the recycling for plastic, metal and paper waste streams have declined by 60 per cent in the same period due to the contamination in recycling bins caused by food and liquid waste, making them unsuitable for recycling. This same problem persists across Singapore.”

“Having a better understanding of the recycling behaviour of our community will therefore help us design new and improved strategies to encourage more effective recycling habits,” he added.   

A detailed waste contamination analysis, the first in NUS, was carried out as part of the study. The research team, comprising students majoring in industrial design, statistics and engineering, spent about 120 hours over 42 days ‘dumpster diving’ to sort the contents of more than 2,150 recycling bags in UTown and NUS Engineering to determine the proportion of non-recyclables and recyclables in recycling bins.


The research team conducting a waste composition analysis of recycling bin contents

The team’s analysis revealed that the contamination rate (proportion of non-recyclables vs recyclables) for plastic recycling bins before any recycling intervention was introduced, was high at an average of 57 per cent and 46 per cent for UTown and NUS Engineering respectively. The metal recycling bins, on the other hand, had a lower contamination rate of 37 per cent and 15 percent at UTown and NUS Engineering respectively.

Contamination was also found to be higher in recycling bins placed near food establishments, and lower when the recycling bins were paired with rubbish bins without lids.


The typical contents of a plastic recycling bin with a high level of contamination, such as unfinished bubble tea and unrinsed beverage containers

NUS Engineering Masters student Bao Xinjing, who led the contamination analysis said, “From this project, I have learnt how to conduct behaviourial experiments, and the data collection process was thought provoking to me. Even though the project was tedious, it was interesting and meaningful.”

Leveraging the data and insights gathered from the contamination analysis, the industrial designers from the research team then test-bedded new recycling bin features aimed at reducing the amount of non-recyclables thrown into recycling bins. These included a recycling ‘speedbump’ to slow down the act of disposal to encourage proper recycling, and an educational ‘Recycle Right’ banner highlighting the common wrong items thrown into recycling bins based on the contamination analysis conducted.   


Recycling ‘speedbumps’ designed by Industrial Design students from NUS Design and Environment

It was observed that the recycling ‘speedbumps’ reduced the contamination rate in the metal recycling bins by about 14 per cent, but both the ‘speedbumps’ and ‘Recycle Right’ banner interventions had no impact on reducing contamination in the plastic recycling bins.

In addition, the students carried out a face-to-face survey with over 350 staff and students who used recycling bins in UTown. Their survey revealed that while the respondents had good knowledge on what could be recycled, about 25 per cent were not aware that used food packaging with some oil stains or bubble tea cups with a few drops of liquid cannot be recycled. These findings explained why the contamination persisted despite the new interventions.

The overall findings from the in-depth behaviourial study have facilitated the research team in proposing recommendations to help improve NUS’ campus recycling programme. These recommendations included a new intuitive recycling bin design, stepping up “Recycle Right” education efforts, and the gradual phasing out of single-use plastics on campus.


A sleek “Recycle Right” bin design featuring a clear display that showcases actual items in the bin and a slide-able opening to reduce mindless throwing of non-recyclables

Tommy Cheong, Year 4 Industrial Design student from NUS Design and Environment who designed the new recycling bin concept, shared his experience. “Testing and iterating my prototypes through experimentation provided valuable insights on how users actually behave as compared to what they say. These insights were then used to develop the new recycling bin to get people to recycle right.”

Year 2  NUS Statistics and Applied Probability student Hemashree A, who conducted the analysis for the project, reflected, “This project has taught me how to apply the quantitative methods I have learnt in my statistics class to a real-world practical setting to produce evidence-based recommendations to decision makers.”

Senior Director (Operations and Maintenance) Mr Chew Chin Huat from NUS University Campus Infrastructure said, “The study conducted by our students provided robust, valuable insights and recommendations to improve our campus recycling programme. We look forward to implementing these recommendations in the new semester to continue encouraging the NUS community to recycle right and reduce waste.”

By the Waste Minimisation and Recycling Taskforce, with support from the NUS Offices of Estate Development and Facilities Management


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