The linear economy has resulted in environmental challenges such as air pollution, biodiversity loss, climate change and resource depletion. In response to these challenges, the circular economy emerges as a promising pathway to sustainability. By embracing efficiency consumption (i.e. consumption oriented toward achieving the same level of affluence with lower material and energy inputs through technological improvements) as well as sufficiency consumption (i.e. consumption oriented toward lowering the level of affluence through changes in consumer attitudes and behaviors), the circular economy enables the generation of not only economic value but also environmental value and even social value. To catalyze the transition to a more sustainable circular economy, researchers, practitioners and policymakers point to actor engagement. This dissertation therefore aims to provide insight into actor engagement with efficiency consumption and sufficiency consumption in the circular economy and the sharing economy (i.e. the subset of the circular 
economy that focuses on sharing under-utilized resources).

Chapter 1 provides insight into actor engagement in the circular economy by focusing on the role of engagement platforms. It discerns that the circular economy encompasses business models that vary in terms of servitization (i.e. the extent to which the circular business model embraces a service rather than a product as unit of exchange) and collectivity (i.e. the extent to which the circular business model requires collective action and collaboration). Furthermore, this chapter expresses that actors engage with these business models in return for benefits, and groups them into four categories: (1) short-term individual benefits, (2) long-term individual benefits, (3) short-term collective benefits, and (4) long-term collective benefits. Moreover, it integrates illustrative examples to underscore the critical role of engagement platforms in connecting actors who seek similar benefits in the circular economy. Finally, this chapter proposes three gaps, inspired by the gaps model. Addressing these gaps can boost the engagement potential of engagement platforms in the circular economy. These gaps lay the foundation for the subsequent chapters of the dissertation.

Chapter 2 provides insight into actor engagement in the sharing economy by responding to the gap related to understanding actor expectations. In particular, it examines engagement with business-to-consumer car sharing business models among Maghrebian and Turkish minority consumers and majority consumers in Western Europe. Furthermore, this chapter embraces social exchange theory to investigate perceived economic value, perceived environmental value, perceived social value, and trust as underlying mechanisms that vary among these minority and majority consumers. Based on a survey design, it finds that Maghrebian an Turkish minority consumers perceive more environmental value of sharing and have less trust in sharing compared to Belgian majority consumers.

Chapter 3 provides insight into actor engagement in the sharing economy by responding to the gap related to translating and meeting actor expectations through business model design choices. It employs a systematic literature review to identify five dimensions along which sharing business models vary: (1) ownership transfer, (2) professional involvement, (3) compensation, (4) digitalization, and (5) community scope. Moreover, this chapter relies on social exchange theory to examine how these dimensions affect engagement with fashion sharing business models among consumers with varying levels of sustainability orientation. Based on a discrete choice conjoint experiment, this chapter finds that ownership of tangible resources elicits more engagement than access to tangible resources for both consumers with a low sustainability orientation and consumers with a high sustainability orientation. Community scope also affects consumer engagement as reflected in more engagement toward sharing business models with a local rather than a global 
scope. The presence of professional service providers, monetary compensation and a digital platform only induces engagement among consumers with a low sustainability orientation. 

Chapter 4 provides insight into actor engagement in the circular economy by responding to the gap related to external communications. Specifically, it embraces terror management theory to investigate the influence of reminders of death on efficiency consumption and sufficiency consumption among consumers with varying levels of sustainability orientation. In doing so, this chapter distinguishes between reminders of one’s own death and reminders of the planet’s death. Based on a between-subjects experimental design, it finds that reminders of the planet’s death result in increased attitudes and intentions toward efficiency consumption among consumers with a low sustainability orientation but does not find similar effects for sufficiency consumption. Finally, the conclusion summarizes the main findings of this dissertation and elaborates on its theoretical and practical implications, limitations and avenues for future research.