The global sustainability crisis, marked by ecosystem damage, resource depletion, and widespread poverty, necessitates enhanced sustainability literacy. The UN's 2030 Agenda emphasizes Education for Sustainable Development (ESD) to foster informed decision-making for a sustainable future. Higher education institutions (HEIs) are crucial in promoting ESD, equipping students across disciplines to become agents of change. Composition studies, with their cross-disciplinary nature, offer a unique platform for integrating sustainability into the curriculum. While some curricular initiatives exist, research assessing the impact of curriculum design on sustainability understanding is limited. This study aimed to enhance students' sustainability literacy by implementing a structured curriculum in a first-year writing course, examining the benefits of using CBI to introduce students to the three dimensions of sustainability and the UN Sustainable Development Goals (SDGs). CBI, a popular approach in language education, effectively combines content and language learning, creating a meaningful context for language use and improving fluency. Although CBI has been explored in various contexts, its impact on sustainability literacy remains under-researched. This research, employing a case study approach, sought to address this gap by investigating the effect of CBI on students' sustainability literacy levels and their perceptions of sustainability challenges and solutions in Kuwait.

The concept of sustainability, while not entirely new, has gained prominence due to population growth, increased consumption, and resource depletion. While there's no universally accepted definition, it generally encompasses environmental, economic, and social aspects. The Brundtland Report's definition, 'development that meets the needs of the present without compromising the ability of future generations to meet their own needs,' remains influential. Sustainability solutions require both organizational and individual decision-making, highlighting the crucial role of individual choices and consumer behavior. Education plays a pivotal role in achieving sustainability goals by fostering informed decision-making and empowering individuals to take action. Various assessment tools for measuring sustainability literacy have been developed, such as the SULITEST and the STARS framework. Kuwait, heavily reliant on oil revenues, faces significant sustainability challenges, including air pollution, water scarcity, and waste management. Despite government initiatives like the Kuwait National Development Plan (KNDP) and the adoption of SDGs, Kuwait's overall sustainability score remains relatively low, indicating a need for greater public awareness and implementation of sustainable practices.

This study utilized a true experimental research design with random assignment of students to control and experimental groups (100 and 121 respectively). A mixed-methods sequential explanatory approach was employed, starting with quantitative data collection and followed by qualitative data analysis. The quantitative phase involved a pretest and a post-test using an adapted version of the Sustainability Literacy Assessment, measuring knowledge, skills, attitudes, and familiarity with sustainability topics and concepts. The qualitative phase involved collecting essays from 60 students in each group, focusing on identifying major sustainability challenges in Kuwait and proposing solutions. Quantitative data were analyzed using SPSS, employing descriptive statistics, chi-square analysis, independent t-tests, dependent t-tests, and one-way ANOVA. Qualitative data were analyzed using MAXQDA, employing quantitative and qualitative content analysis to identify recurring themes and keywords related to sustainability.

The experimental group showed statistically significant improvements in their sustainability literacy levels compared to the control group. Post-test scores revealed significantly higher knowledge scores for the experimental group (p < 0.05). Independent t-tests also demonstrated significantly higher post-test scores in skills, attitudes, and familiarity with sustainability topics and concepts for the experimental group. Qualitative content analysis of the essays revealed that students in the experimental group identified a wider range of sustainability challenges and proposed more solutions, particularly within the social dimension. Specifically, the experimental group more frequently identified social issues such as corruption, gender inequality, and the quality of education as major sustainability challenges, while the control group primarily focused on environmental issues. The experimental group also utilized significantly more sustainability-related keywords in their essays, as determined by dictionary-based content analysis, despite having a slightly lower overall word count compared to the control group.

The findings strongly support the effectiveness of CBI in enhancing students' sustainability literacy. The significant improvements in knowledge, skills, attitudes, and the identification of social sustainability challenges demonstrate the course's impact. These results are consistent with previous research highlighting CBI's effectiveness in language learning. The study's findings also emphasize the importance of integrating sustainability into language education, aligning with a growing trend in EFL and other contexts. The higher frequency of social sustainability issues identified by the experimental group indicates the CBI's success in broadening students' understanding beyond environmental concerns, addressing a gap in current sustainability education research. The increased usage of sustainability-related keywords indicates improved comprehension and application of relevant terminology. Overall, this study provides evidence of the positive impact of focused interventions for improving sustainability literacy.

This study demonstrates the effectiveness of incorporating sustainability into a first-year composition course using content-based instruction. The significant improvement in students' sustainability literacy, particularly their awareness of social sustainability issues, highlights the potential of interdisciplinary approaches to enhance sustainability education. Future research could explore the long-term impact of CBI on students' sustainability knowledge and behavior, investigate the effectiveness of CBI across diverse student populations, and expand the scope of sustainability topics covered in the curriculum.

The study's relatively short duration (6 weeks) and focus on a specific student population limit the generalizability of the findings. The reliance on a single faculty member's course design and materials may limit the transferability of the results. Furthermore, the lack of long-term follow-up prevents assessment of knowledge retention and behavioral changes over time. Future studies could address these limitations by incorporating longer-term evaluations, diverse settings, and alternative pedagogical approaches.