Citizen Science-Based Waste Diaries: An Exploratory Case Study of Household Waste in Switzerland

Sustainable Development Goal 12 (SDG 12) and national waste reduction goals require frequent waste analyses for monitoring and governance decisions. We developed and tested a citizen science (CS)-based household waste diary for ten consecutive days with 89 volunteer households in Switzerland as a complementary monitoring option to official composition analyses. Discrepancies between the CS-based household diary data and the official composition analyses ranged between 55–65% less reported waste quantities for minerals, compound products, and plastics and 80–90% less for paper, avoidable food waste, and glass. Household waste diaries should be digitalized and prolonged to 21–28 days, and volunteers from different demographic groups are needed to produce stratified, representative results. We conclude that a hybrid CS study design involving waste composition analyses and waste diaries could reduce self-reporting biases while increasing the monitoring frequencies of household waste compositions. CS-based hybrid household waste projects can be a powerful means to complement the measures identified in the 2022 Swiss action plan against food waste and for data reporting for the SDG 12.3 Food Waste Index.