Abstract
The accelerating consumption of single-use plastics (SUPs) poses an urgent environmental challenge, demanding innovative strategies that influence both individual behaviours and systemic conditions. This thesis investigates how social marketing can contribute to reducing SUPs, with a specific focus on milk bottles in Aotearoa New Zealand, where dairy packaging represents a critical yet underexplored dimension of plastics waste. Building on the recognition that behavioural change requires both individual-level (I-level) and system-level (S-level) interventions, this research develops and applies a comprehensive social marketing approach that addresses the interdependencies between citizens and the systems that shape their everyday choices.
The thesis unfolds across four interrelated studies. The first presents a systematic synthesis of I-level and S-level interventions designed to reduce SUPs consumption globally. The review highlights the predominance of downstream, individual-focused campaigns and the relative neglect of system-wide reforms, while underscoring the complementary value of integrating both approaches. The analysis demonstrates that durable change occurs when motivated individuals are supported by enabling infrastructures, policies, and market designs.
The second study explores the barriers and enablers influencing consumers’ capability, motivation, and opportunity to reduce SUPs milk bottles, guided by the Capability-Opportunity-Motivation-Behaviour (COM-B) model. Qualitative findings reveal that while many consumers express willingness to adopt sustainable practices, constraints such as limited infrastructure, convenience culture, and economic considerations inhibit behaviour change. This study advances understanding of how motivational and contextual factors intersect to shape consumer decisions in packaging use.
The third study introduces the Theory-Individual-System-Intervention (TISI) framework, a novel social marketing model designed to guide citizen mobilisation for a circular plastics economy. TISI integrates theory application with dual-level change strategies and intervention planning, positioning citizens not merely as passive consumers but as active participants in shaping system transformation. Using SUPs milk bottles as an illustrative case, the framework demonstrates how marketing can align behavioural insights with systemic levers to build collective action.
The fourth study examines public opinion on strategies to reduce SUPs milk bottles, employing mixed methods including interviews and best-worst scaling. Results show that citizens value interventions that combine communication and incentives with systemic reforms such as refill infrastructure and regulatory measures. Importantly, the findings affirm that public support for change is contingent on perceiving fairness, feasibility, and shared responsibility across consumers, industry, and government.
Together, the studies provide a coherent account of how social marketing can bridge the gap between individual intentions and systemic constraints in the context of SUPs. The thesis contributes theoretically by extending the application of the Behaviour Change Wheel and COM-B to dual-level interventions, and by introducing the TISI framework as a tool for marketing-led citizen mobilisation. Practically, it offers evidence-based recommendations for policymakers, businesses, and advocacy groups seeking to design interventions that are citizen-centred, system-enabled, and socially legitimate.
Overall, this research demonstrates that reducing single-use plastics requires moving beyond isolated consumer campaigns or regulatory bans toward an integrated social marketing approach. By engaging both individuals and systems in co-creating solutions, this thesis advances the potential for marketing to serve not only markets but also society, contributing to a circular economy and a more sustainable future.