Explaining a plastic waste reduction behavior: An extended model of the Theory of Planned Behavior applied to refillable bottle use in university students and nonstudent adults

The study aimed to examine the psychosocial determinants of using refillable bottles in Italian students and nonstudent adults, testing the Theory of Planned Behavior (TPB) integrated with past behavior and self-identity as a person who uses refillable bottles. So far, few studies exist on this specific behavior, which may have a relevant impact on plastic waste reduction connected to the widespread use of single-use plastic bottles, and other sustainability issues. A two-wave prospective online survey design was implemented. At Time 1, measures of TPB primary constructs (i.e., attitude, subjective norm, perceived behavioral control, and intention), past behavior, and self-identity were collected. At Time 2, the self-report target behavior of using refillable bottles was measured. After verifying the psychometric properties of the instruments employed, data were submitted to structural equation modeling through reliability estimates and confirmatory factor analysis. Results endorsed that the extended TPB model adequately explained and predicted intention (73% of variance) and target behavior (68% of variance). At Time 1, attitude, perceived behavioral control, and self-identity were associated with intention which, in turn, was linked to refillable bottle use at Time 2. Past behavior predicted intention at Time 1 and target behavior at Time 2 both directly and indirectly. Multi-group analysis showed that the effect of self-identity on intention was stronger in the nonstudent adults than in the student sample, thus raising interesting questions for scholars and practitioners related to the possible self-presentation strategies mediated by these items. Concerning mean differences, students showed higher scores on attitude toward refillable bottles, perceived easiness of use, and intention of using them than adults. All this aligns with younger people being portrayed as more committed to promoting eco-friendly ways of life, starting with their habits. The results offer insights for designing interventions to promote the investigated pro-environmental behavior.