Beyond theory of planned behavior: A meta-analysis of psychological and contextual determinants of household waste separation

Household waste separation plays a critical role in supporting recycling and sustainability goals, yet the psychological drivers of this behavior across diverse contexts remain insufficiently synthesized. This study presents a comprehensive meta-analysis of 46 studies (50 independent samples, N = 30,250), grounded in the Theory of Planned Behavior (TPB) and its extensions. The results confirm that waste separation behavior is most strongly associated with perceived behavioral control, intention, infrastructure, publicity and education, and attitude. Intention is positively associated with attitude, perceived behavioral control, moral norm, subjective norm, consequence awareness, and past behavior. Significant heterogeneity was detected, with meta-regression identifying age, gender, Human Development Index of the study region, and study quality as key moderators. Building on these findings, we identify a range of influential external factors—such as moral norms, past behavior, consequence awareness, and contextual enablers like infrastructure and education—as well as heterogeneity factors, including socio-demographic and contextual moderators that shape the strength and direction of TPB relationships. To integrate these dimensions systematically, we propose a novel theoretical framework: TPB + E(xternal) + H(eterogeneity), an extended behavioral model that expands the Theory of Planned Behavior by incorporating External influences (E) and Heterogeneity (H). This framework challenges the assumption of universality inherent in traditional TPB applications and underscores the need to account for individual and contextual variation in pro-environmental behavior. These findings thus provide not only theoretical refinement but also clear implications for developing targeted psychological and contextual interventions—such as raising awareness and improving infrastructure—to effectively promote household waste separation worldwide.