Sustainability, as a complex competence, has been approached through various frameworks, including the European Competence Framework for Sustainability. This outline defines competency areas such as embodying sustainability values, embracing sustainability complexities, envisioning sustainable futures, and acting towards sustainability. Additionally, other authors have proposed key competencies for sustainability, encompassing systems thinking, values, anticipation, strategy, interpersonal sub-competencies, and integrated complex problem-solving. Collectively, sustainability competencies are essential in educational programs to help students acquire knowledge and skills that foster sustainable thinking, planning, and acting with empathy, responsibility, and planet care.

Prior studies have highlighted the benefits of collaboration between university and vocational training, which can be understood through Vygotsky's sociocultural theory and his concept of the "zone of proximal development." Whereas students had previous experience developing sustainability as a complex competency, particularly in systems thinking, anticipatory, and strategic sub-competencies, they lacked experience in interpersonal and complex problem-solving.

To address this, an interdisciplinary, collaborative learning activity was implemented within Elkarhezi project. This initiative involved undergraduate students in Human Nutrition and Dietetics Degree from the University of the Basque Country (UPV-EHU) and students from a vocational education training course in Culinary Management at Gamarra Hospitality and Catering School. The methodology followed a challenge-based approach, focusing on the creation of different gluten-free breads that met nutritional safety and inclusivity standards, thus promoting sustainability in a holistic manner.

Thirty students participated in this pilot study, and validated and/or published surveys were used to assess interpersonal and problem-solving sub-competencies. Pre- and post-activity comparisons showed improvement in collaborative learning areas, including social skills, group processing, positive interdependence, and promotion of interaction. Social skills and group processing displayed the most relevant improvement, as both scored low on the initial 0-20 scale but increased after the activity. Problem-solving competency data remain descriptive, providing insights into which areas benefitted most from the joint activity. Overall, the average performance rating in the gluten-free bread creation report was 7.12 ±1.47, indicating a medium-high level of achievement.

These findings suggest that this collaborative activity is relevant and effective in its current format. While it represents an isolated activity, it forms part of the broader Elkarhezi networking and coeducation program aimed to fostering sustainability competencies through collaborative learning.

Keywords: Sustainability competence, interdisciplinary collaboration, challenge-based learning, problem-solving competency.