An integrative model of project-based learning for sustainability in engineering capstones: insights from students across industry-based and service-learning contexts

This study investigates how engineering capstone projects influence students’ academic motivation and understanding of sustainable development. Drawing on qualitative interviews with twenty final-year engineering students, it examines how course design, basic psychological need satisfaction, and project contexts shape students’ capstone learning experiences. The findings indicate that perceived competence gaps, structured autonomy, and interdisciplinary collaboration serve as powerful motivators. In contrast, time constraints, competing academic priorities, limited budgets and resources, and insufficient stakeholder engagement constrain opportunities for deeper learning, experimentation, and critical reflection. Although most participants initially viewed sustainability primarily through an environmental perspective, those involved in service-learning projects developed a broader understanding that encompassed engineers’ social responsibilities and the Sustainable Development Goals. Based on these findings, the study proposes a transferable integrative model of project-based learning that demonstrates how contextual factors, basic psychological need satisfaction, and motivational regulation interact to foster academic motivation and sustainability-oriented learning in engineering capstone education.