Effect of Household Interventions on Promoting Waste Segregation Behavior at Source: A Systematic Review

Waste segregation at the source is one of the most important strategies of urban waste management and the first environmental priority. This systematic review study was conducted to determine the effects of various interventions to promote household waste segregation behavior. Studies were searched in the Web of Science, Scopus, and PubMed databases using the keywords "waste segregation, intervention, randomized controlled trials, and clinical trials". Through 2 January 2022, two researchers were independently involved in article screening and data abstraction. Inclusion criteria were as follows: experimental and quasi-experimental studies where primary outcomes of the studies included improvement in waste separation behavior, and secondary outcomes of the studies included increased knowledge and improvement in psychological factors. Articles that did not focus on households, studies that focused only on food or electronics separation, and studies that focused only on recycling and its methods were excluded. Of the original 5084 studies, only 26 met the inclusion criteria after reviewing the titles, abstracts, and full texts of the articles. The age of study participants ranged from 15 to 82 years. It seems that most of the studies that suggest higher efficacy consider older age groups for the intervention. Positive results of the interventions were reported in all studies with different ratios; in five studies, the improvement in results was more than 20%. Meta-analysis was not possible because of the diversity of study strategies and outcomes measured. In the studies that lasted longer than two months, people's waste separation behavior was more permanent. Approaches such as engagement, feedback, and theory-based interventions have been effective in promoting waste separation behavior. Interventions that considered environmental, social, and organizational factors (such as segregation facilities, regular collection of segregated waste, tax exemption, and cooperation of related organizations) in addition to individual factors were more effective and sustainable. For the comparison of studies and meta-analysis of data, it is suggested to use standard criteria such as mean and standard deviation of waste separation behavior and influential structures such as attitude and norm in studies. The results show that it is necessary to use environmental research and ecological approaches and intermittent interventions over time to maintain and continue waste separation behavior. Based on the results of the current research, policy makers and researchers can develop efficient measures to improve waste sorting behavior by using appropriate patterns in society and knowing the effective factors.