Integrating Project-Based and Community Learning for Cross-Disciplinary Competency Development in Nutrient Recovery

Abstract

This study presents a vertically integrated Project-Based Learning (PBL) and Community-Based Learning (CBL) framework that connects postgraduate and undergraduate programs in Applied Chemistry and Agricultural Engineering. Postgraduate students synthesized zeolite-based materials for nutrient recovery, which were subsequently applied by undergraduate students in field trials conducted in collaboration with rural farming communities. The project was evaluated using rubrics, surveys, focus groups, and reflective journals. Results demonstrated substantial development of technical, communication, and critical thinking skills, with students highlighting the value of linking theory to practice. Community feedback confirmed the perceived benefits of the material for soil improvement and fertilizer efficiency, while also underscoring the need for sustained engagement. Despite challenges such as curricular coordination and resource constraints, the model effectively fostered interdisciplinary learning and social impact. These findings highlight the contribution of this sequentially instructional design to STEM education by connecting research, teaching, and outreach within a constructivist, sustainability-oriented approach.

1. Introduction

1.1. Pedagogical and Methodological Foundations

Higher education faces critical challenges in preparing professionals capable of effectively addressing complex, real-world problems [1,2]. The demands of today’s labor market increasingly require interdisciplinary competencies that bridge academic instruction with practical application [3,4,5]. However, many students struggle to translate theoretical learning into applied critical thinking within their respective fields [6,7]. A key challenge in contemporary higher education, therefore, lies in developing core competencies that enable students to engage with authentic problems in real-life contexts [8,9]. Traditional educational models have often prioritized theoretical content at the expense of professional preparation [10]. Without opportunities to apply learning in authentic settings, students frequently lack the confidence, technical expertise, and adaptability required for professional success [11,12].

Project-Based Learning (PBL) is a student-centered pedagogical approach that emphasizes active participation in real-world projects [13]. Unlike traditional models focused primarily on theoretical instruction [14], PBL fosters the integration of theory with practice by involving students in the resolution of authentic problems [15,16]. This methodology encourages motivation and deep learning through meaningful, collaborative activities, supporting the development of research, critical thinking, and problem-solving abilities [17,18]. PBL has been widely adopted in higher education for its proven effectiveness in promoting academic achievement and in strengthening the professional and personal competencies necessary for career success [19]. By engaging in project-based tasks, students not only apply theoretical knowledge but also adapt it to real-life contexts, thereby addressing practical challenges [14].

Numerous studies confirm the success of PBL in enhancing student engagement and learning outcomes across disciplines, particularly in engineering and applied sciences [20,21]. In this study, PBL is integrated with Community-Based Learning (CBL), a methodology that promotes ongoing collaboration with local stakeholders. This approach enables students to co-create and implement contextually relevant solutions, strengthening the connection between academic theory and professional practice [22,23]. CBL situates learning within community contexts, reinforcing the alignment of academic training with societal impact [24,25]. Universities, as institutions of knowledge production and social transformation, are particularly well positioned to incorporate CBL in ways that enhance student learning while addressing community needs [26,27]. Through the curricular integration of CBL, institutions not only support community development but also foster civic responsibility, strengthen professional competencies, and generate meaningful social impact [28]. Within this framework, Participatory Action Research (PAR) further supports CBL by enabling inclusive collaboration between students, faculty, and community members throughout all phases of a project. PAR enhances the social relevance of knowledge and fosters mutual learning and transformation, recognizing local stakeholders as co-researchers in the development of sustainable, context-appropriate solutions [29,30,31].

To respond effectively to today’s interconnected societal challenges, a multidisciplinary educational framework is essential [32,33]. This study exemplifies such a framework by integrating students from the undergraduate Agricultural Engineering program and the master’s program in Applied Chemistry in a joint academic initiative grounded in a combined Project-Based Learning (PBL) and Community-Based Learning (CBL) model. Students were actively involved in all stages of the project, from problem definition through implementation to results dissemination. This integration of teaching and research enabled students to acquire both technical and professional competencies while addressing pressing local needs [34,35]. Such community-engaged academic experiences not only enrich student learning but also deliver practical solutions to real-world challenges [36,37].

This work presents a case study illustrating how the combination of PBL and CBL was employed to foster both technical and social competencies among students. By engaging in a real-world project with clear societal relevance, students applied their theoretical knowledge in practice while contributing to local development, thereby reinforcing their professional purpose and social responsibility. The project was embedded within the curricula of both the master’s program in Applied Chemistry and the undergraduate program in Agricultural Engineering, establishing a collaborative platform between the two. The outcomes of this project generated tangible benefits for a rural community [38]. Specifically, the project focused on the synthesis and application of modified zeolites for nutrient recovery from treated wastewater. These recovered nutrients were evaluated as alternative fertilizers in agricultural soils in the rural community of San Cayetano, where food security and sustainable production are critical concerns. The project enabled students to engage in the development and application of sustainable technologies, benefiting the community while equipping students with essential professional competencies [39].

The educational framework of this study is firmly grounded in constructivist theory and the principles of social learning. Constructivism asserts that knowledge is not passively absorbed but actively constructed through learners’ experiences and interactions with their environment [40,41]. In this context, the combined use of Project-Based Learning (PBL) and Community-Based Learning (CBL) closely aligns with constructivist principles, immersing students in real-world problem solving and encouraging deeper understanding through active participation. Social learning theory further reinforces this approach by emphasizing the critical role of interaction and observation in the learning process [42]. By engaging in collaborative work in both laboratory and field settings, students were able to learn from peers, instructors, and community stakeholders. These peer-to-peer and student-to-community interactions facilitated the co-construction of knowledge and strengthened interpersonal skills essential for professional development.

Project-Based Learning (PBL) and Community-Based Learning (CBL) foster environments where students actively participate in their learning through scaffolding, reflection, and collaboration, principles rooted in constructivist and social learning theories. The integration of Participatory Action Research (PAR) further reinforces this by positioning stakeholders as co-creators of knowledge, bridging academic theory with real-world practice, and generating more relevant and impactful learning outcomes [29]. Although numerous studies have applied community-based learning (CBL) and project-based learning (PBL) strategies in STEM education, most remain limited to a single academic level or emphasize pedagogical development over technical applications. For example, PBL models often stress real-world problem solving but are usually confined to one educational stage, even in an interdisciplinary context [43,44,45,46,47,48]. Doğantan et al. (2025) report positive outcomes from integrating PBL with information and communication technologies in a Tourism Management undergraduate program, which enhanced students’ higher-order thinking, collaboration, and problem-solving skills; however, the initiative was restricted to undergraduates and primarily pedagogical in scope [43]. Similarly, Naseer et al. (2025) propose industry-enriched PBL frameworks to improve employability and professional readiness [44]. Their findings show that involving external stakeholders fosters authentic problem solving and career-oriented learning, yet they also note that such approaches require sustained partnerships and institutional commitment, conditions often difficult to achieve in resource-constrained contexts. Sánchez-García et al. (2025) emphasize the need to align project-based learning frameworks with curricular structures to enhance sustainability education [45]. Their review highlights the benefits of integrating cognitive, socio-emotional, and interdisciplinary dimensions, but also identifies limitations such as uneven fidelity to PBL principles, insufficient reflection opportunities, and limited teacher training. Novalia et al. (2025) demonstrate that while PBL fosters metacognitive skills, self-confidence, responsibility, discipline, and readiness for lifelong learning, cross-level initiatives remain rare [46]. They also underline persistent challenges, including time management difficulties, uneven student engagement, and dependence on external support. Bolick et al. (2024) demonstrate that authentic interdisciplinary projects increase motivation, collaboration, and relevance, confirming the pedagogical value of real-world tasks [47]. Yet, they caution that faculty workload, the lack of continuity once funding ends, and rigid curricula threaten long-term sustainability. Similarly, Mutanga (2024) highlights students’ perspectives, showing how PBL enhances autonomy, critical thinking, and problem solving, but also brings adaptation challenges related to group dynamics, workload, and inconsistencies when blended with traditional instruction [48]. Mahmud et al. (2024) reinforce the societal relevance of community-centered engineering projects, noting that they build technical competencies and stakeholder engagement but rarely integrate postgraduate research or material development, limiting scalability [49]. Complementing this, PAR-based initiatives often demonstrate strong community involvement but lack structured curricular integration. Tremblay-Wragg et al. (2025), Smith et al. (2024), and Mitwalli et al. (2025) document impactful collaborations, yet these remain confined to either undergraduate or postgraduate contexts, without mechanisms for cross-level articulation or structured knowledge transfer [50,51,52]. Tremblay-Wragg et al. (2025) demonstrate how participatory action research (PAR) can support the professionalization of emerging scholars by fostering project management, collaboration, communication, and digital literacy, while reducing the isolation often associated with graduate research [52]. However, they also note persistent challenges, including unequal access due to financial or workload constraints, the sustainability of participation, and the persistence of hierarchical dynamics despite horizontal governance strategies. Smith et al. (2024) extend this perspective by applying youth participatory action research to adolescent mental health, showing how positioning students as co-researchers strengthens empowerment, reflection, and transferable skills such as collaboration and communication [51]. Nonetheless, their study highlights barriers such as unequal power relations, intensive resource requirements, and the difficulty of embedding PAR within formal curricula. Complementing these works, Mitwalli et al. (2025) focus on marginalized youth with disabilities in the Israeli-occupied Palestinian territory, demonstrating how full involvement in the research process enhances self-confidence, leadership, and policy influence [50]. Yet, this study also underscores critical constraints, including high resource demands, limited funding, and contextual challenges linked to political instability and infrastructural deficits, all of which threaten long-term sustainability.

Collectively, these studies highlight the transformative capacity of PAR to foster empowerment, professional identity, and social impact, while simultaneously exposing systemic barriers that restrict scalability and integration across academic levels. To date, few documented cases exist in which postgraduate and undergraduate activities are scaffolded within sequential, interdisciplinary instructional models that combine direct community outreach with measurable technical outcomes. The approach presented in this study addresses this gap by linking postgraduate material development with undergraduate field implementation through coordinated curricular designs, offering a distinctive contribution to evolving literature on PBL, CBL, and PAR in STEM education.

Building on these precedents, this study introduces a sequenced Project Based-Learning (PBL) and Community Based-Learning (CBL) model that integrates postgraduate and undergraduate levels within an interdisciplinary, community-oriented framework. While similar initiatives have been reported, to the best of our knowledge, this is among the first systematically documented cases in which postgraduate students in Applied Chemistry developed and characterized nutrient-enriched zeolites that were subsequently implemented and evaluated in agricultural contexts by undergraduate students in Agricultural Engineering. This vertically integrated design supports scaffolded learning, cross-level collaboration, and tangible community outcomes, contributing an innovative model to the literature on sustainability education. The approach not only reinforces competency-based education and translational research but also aligns with broader sustainability goals and the needs of local farming communities. By prioritizing the academic and pedagogical experience alongside technical outcomes, this study provides valuable insights into how interdisciplinary models can effectively connect theoretical knowledge with real-world application in higher education. The study was guided by the following research questions:

• How does participation in an integrated PBL–CBL initiative enhance students’ interdisciplinary technical skills and professional competencies across the Applied Chemistry and Agricultural Engineering programs?
• To what extent are students satisfied with the PBL–CBL model, and which components (e.g., laboratory experimentation, fieldwork, community engagement) do they find most impactful?
• How do participating farmers, based on focus group feedback, evaluate the relevance, practicality, and benefits of the student-developed nutrient-recovery zeolite for sustainable agriculture?

1.2. Technical Rationale and Project Relevance

1.2.1. Environmental Sustainability Challenges in Agriculture

Modern agriculture is increasingly challenged by environmental issues, particularly those associated with the excessive use of synthetic fertilizers. These inputs often result in nutrient leaching and eutrophication in nearby water bodies, leading to ecological degradation and reduced nutrient-use efficiency in soils [53,54]. The depletion of essential elements such as phosphorus and nitrogen not only hinders crop productivity but also exacerbates environmental deterioration [55,56]. With global phosphorus reserves projected to reach critical limits within the coming decade, the search for alternative nutrient sources has become an urgent global priority [57,58]. This project addresses these concerns by exploring nutrient recovery from treated wastewater using zeolites, naturally occurring aluminosilicate minerals recognized for their high adsorption and retention capacities [59,60].

1.2.2. Zeolites for Nutrient Recovery

The use of zeolites as soil amendments is well established in the scientific literature. Natural zeolites, such as clinoptilolite and mordenite, exhibit a strong affinity for nitrates and phosphates, making them highly effective for wastewater treatment and as slow-release nutrient sources in agriculture [61,62,63]. This project builds on previous research conducted by the Advanced Materials and Pharmaceutical Prototyping Innovation Group, which demonstrated that both natural and chemically modified zeolites can efficiently recover nutrients from wastewater while simultaneously improving soil quality and promoting plant growth.

1.2.3. Local Context in Ecuador

Despite their demonstrated benefits, zeolite-based nutrient recovery technologies remain largely underutilized in Ecuador. For example, the wastewater treatment plant in the city of Loja lacks tertiary treatment stages dedicated to nutrient removal. Consequently, nitrogen and phosphorus are discharged untreated into natural ecosystems, contributing to water pollution and limiting agricultural productivity. This situation is compounded by farmers’ limited confidence in alternative practices, due to inconsistent crop yields and a lack of access to sustainable methods. Zeolite-based adsorption technologies offer a cost-effective and scalable solution for nutrient recovery that can be integrated into existing infrastructure [64]. This project aims to close the gap between academic research and practical implementation by transferring laboratory-developed technologies into community contexts. Master’s students in the Applied Chemistry program were trained in material synthesis, water treatment through adsorption technologies, and the development of value-added products. In parallel, undergraduate students from the Agricultural Engineering program conducted field trials with the recovered nutrients. This collaborative educational model reinforced the practical relevance of academic learning in addressing community-based sustainability challenges.

1.2.4. Curricular Impact of Technical Methodologies

From an academic perspective, integrating postgraduate students from the master’s program in Applied Chemistry with undergraduate students from the Agricultural Engineering program created a meaningful, practice-based learning experience that linked theoretical knowledge with real-world challenges. This pedagogical approach not only enhanced student learning outcomes but also benefited rural communities through knowledge transfer and technical support for improved farming practices. The project aligns with the broader mission of higher education to prepare professionals capable of addressing complex social and environmental challenges by combining theoretical training with applied practice [8]. The combined use of Project-Based Learning (PBL) and Community-Based Learning (CBL) provided students with experiential learning opportunities embedded in authentic, real-world contexts.

By addressing critical environmental issues such as eutrophication and sustainable agriculture, students gained direct experience in applied fields essential for their professional development. At the same time, the project’s community-oriented focus promoted the adoption of sustainable agricultural practices. Through this integrated PBL–CBL framework, students strengthened their technical, analytical, and research competencies while contributing to the design and implementation of nutrient-recycling solutions tailored to smallholder farming systems. This innovative educational model, linking postgraduate and undergraduate curricula through community-engaged research, represents a novel contribution to interdisciplinary STEM education. These pedagogical and technical foundations informed the design of project activities, as described in the methodology section. A dedicated technical manuscript will separately report the synthesis, physicochemical characterization, and adsorption performance of the modified zeolite materials. However, a concise technical summary has been included in the Supplementary Materials section of this manuscript (Section S1: Brief Technical Report on Zeolite-Based Adsorbent Preparation and Field Application).

2. Materials and Methods

2.1. Structured Planning for the Project-Based Learning Experience

A planning matrix was developed to guide the implementation of the Project-Based Learning (PBL) methodology applied in this study (

Table 1. PBL planning matrix detailing structured steps for interdisciplinary learning and community engagement.

Step 1. Determine Learning Outcomes	Step 2. Restate the Driving Questions		Step 3. Determine the Details of the Culminating Event
Academic content—theoretical knowledge Agricultural Engineering program: Edaphology: soil science, sustainable agricultural practices, and nutrient management. Topics: Soil origin and evolution Rocks and minerals Importance and profile of soil Physical and chemical soil properties Soil organic matter Soil sampling Soil ecology Applied chemistry program: Catalysis: chemical properties of zeolites, and adsorption processes. Topics: Introduction to catalysis Basic principles of catalysis Adsorption on solid surfaces Kinetics of catalyzed reactions Heterogeneous catalysis Preparation of heterogeneous catalysts Techniques for catalyst characterization Application of catalysts across various industrial sectors Study of reaction types: chemical and petrochemical Selective adsorbents for water decontamination Applications in decontamination: dyes, heavy metals, and organic and inorganic contaminants Skills and competencies: Teamwork Research and critical thinking. Collaboration and communication. Project management Goal: enable students to connect theoretical concepts with practical applications and collaborate effectively on real-world problems.	Research questions: How does participation in an integrated PBL–CBL initiative enhance students’ interdisciplinary technical skills and professional competencies across the Applied Chemistry and Agricultural Engineering programs? To what extent are students satisfied with the PBL–CBL model, and which components (e.g., laboratory experimentation, fieldwork, community engagement) do they find most impactful? How do participating farmers, based on focus group feedback, evaluate the relevance, practicality, and benefits of the student-developed nutrient-recovery zeolite for sustainable agriculture? Product: A comprehensive pedagogical model demonstrating the integration of theory and practice through PBL. Guidelines for implementing an interdisciplinary learning experience, linking academic content with community-centered environmental and agricultural challenges. Purpose: Bridge academic with experiential learning, enabling students to acquire transferable skills directly applicable to sustainability issues in their local context. Audience: University stakeholders (faculty, curriculum designers, academic coordinators). Educators interested in interdisciplinary, community-based models. Institutions promoting project-based learning methodologies. Local farmers and members of the San Cayetano community. Local government and environmental agencies.		Community workshop: students present findings and demonstrate the application of modified zeolite in local farming, with recommendations for broader adoption. Field demonstration: comparative showcase of zeolite-amended plots versus conventional fertilizer use.
Step 4. Sequence the calendar and milestones	Step 5. Plan scaffolding and assessments	Step 6. Plan the entry event	Step 7. Plan for productive group work
Timeline and Milestones Project launch: introduction of guiding questions, formation of interdisciplinary teams, and clarification of expected learning outcomes. Literature review: topics include soil science, eutrophication, zeolite chemistry, and key performance indicators. Laboratory work: zeolite modification (e.g., metal doping), and initial adsorption experiments. Field setup: coordination with local farmers and establishment of pilot plots. Application and monitoring: zeolite use in test plots and monitoring of soil and plant performance. Data analysis: integration of laboratory and field results, with refinement of methodologies as needed. Workshop preparation: development of presentations and materials for community outreach. Community workshop and feedback session. Final assessment: reflection reports, student self-assessments, and project evaluation.	Scaffolding Mini-lectures and technical workshops on key theoretical concepts. Hands-on experiments and collaborative data analysis. Peer feedback and problem-solving sessions. Assessment methods: Formative: laboratory journals, quizzes, and iterative feedback on experimental work. Individual: exams testing comprehension of core chemical and agricultural concepts. Group: compilation of project results, lessons learned, and scalability evaluation. Overall Experience: self-assessment focused on connecting theory with real-world problem-solving.	Entry event Immersion activity: guided visits to wastewater treatment facilities and nutrient-depleted farms. Visual stimulus: case studies on eutrophication and nutrient recovery innovations. Problem framing: group discussions addressing issues such as reduced yields and water pollution. Objective: stimulate engagement and contextual awareness, motivating students to take ownership of the project.	Productive group work Team formation: based on shared interest and complementary skills. Collaborative infrastructure: tutors monitored progress, managed tasks, and ensured adherence to deadlines. Shared platforms (e.g., Google Drive) were used for data, references, and presentations. Reflective journals encouraged personal development and teamwork. Outcome: a collaborative learning environment that maximized student participation and promoted shared responsibility for the project success.

), adapted from the 7 Steps for PBL Planning [49]. This framework was tailored to the interdisciplinary scope of the project, which involved students from both the Agricultural and Applied Chemistry programs. It ensured a cohesive learning experience by integrating academic content, skill development, and community engagement. The planning phase began with a needs assessment in the San Cayetano community, where the Technical University of Loja, through the Faculty of Exact and Natural Sciences, had previously conducted research and outreach activities. Community needs were identified using a participatory approach that included direct consultations with residents. During these discussions, community members emphasized the importance of improving agricultural practices, citing the absence of technical support and institutional guidance, which had forced many families to rely solely on local resources for subsistence farming.

Aligned with the curricular objectives of the master’s program in Applied Chemistry and the undergraduate Agricultural Engineering program, key issues such as soil degradation and the high cost of conventional fertilizers were identified. These insights shaped the project’s objective and action plan, which was integrated into an ongoing research initiative evaluating modified zeolites as low-cost adsorbents for tertiary wastewater treatment in the city of Loja. Students participated actively from the project design stage through to its field implementation.

2.2. Project Description

This project was implemented over two academic terms: October 2021–February 2022 and April 2022–August 2022. Each term addressed a distinct phase of the initiative. The project fostered interdisciplinary learning by engaging postgraduate students from the master’s program in Applied Chemistry together with undergraduate students from the Agricultural Engineering program. The institution’s ongoing research in this field provided an ideal platform to bridge academic inquiry with educational practice and community-based challenges.

2.2.1. Phase One (October 2021–February 2022)

This phase involved nine postgraduate students enrolled in the Catalyst course of the master’s program in Applied Chemistry. The project was embedded within their coursework, emphasizing theoretical foundations of material synthesis and adsorption processes. Laboratory activities focused on the chemical modification of natural zeolites, adsorption kinetics, and material characterization techniques. As part of the practical component, the modified zeolites were evaluated for their capacity to adsorb phosphate and ammonium from treated effluent collected at the Loja Wastewater Treatment Plant through batch adsorption experiments. Adsorption capacities were quantified, and the zeolitic materials were subsequently characterized and stored for later application in field trials. This phase provided students with hands-on experience in the synthesis and application of functional materials for environmental remediation.

2.2.2. Phase Two (April 2022–August 2022):

In the second phase, the project was carried out with twenty-four undergraduate students enrolled in the Edaphology course of the Agricultural Engineering program. The nutrient-loaded zeolites synthesized during the first phase were applied as alternative slow-release fertilizers in experimental plots located in the San Cayetano community. Students conducted practical evaluations of soil quality and plant development, integrating these findings with the theoretical content of their course. They actively monitored crop growth and documented performance indications, gaining direct experience with real-world agricultural processes. The results were shared in a dissemination workshop, where students presented the potential benefits of adopting this sustainable practice, effectively linking academic learning with practical assessments of soil fertility and crop yield.

2.3. Implementation Timeline

The project was structured in sequential stages, each aligned with the academic calendar of the participating cohorts. The postgraduate stage was conducted within the master’s program in Applied Chemistry (Catalysis module), spanning four intensive weeks focused on material synthesis and laboratory evaluation. This was followed by an undergraduate stage in the Agricultural Engineering program, carried out across a full academic term and centered on field application, agronomic monitoring, and community engagement.

Table 2. Project implementation timeline: sequential stages, participants, and key activities.

Stage	Timeline	Participants	Key Activities
Postgraduate stage	October 2021–February 2022	Master’s students in Applied Chemistry (Catalysis course)	- Presentation of the needs assessment conducted in the San Cayetano community. - Project induction and team formation - Synthesis of Fe-Mn-Zn-modified mordenite zeolites - Physicochemical characterization (XRD, FTIR, BET) - Adsorption tests with wastewater (NH4+ and PO43− removal) - Preliminary reporting and 3 kg material scale-up - Consolidation of synthesis protocols, characterization data, and application guidelines - Coordination with Agricultural Engineering faculty
Transition stage	February–March 2022	Faculty coordinators and both student groups	- Handover of materials and data - Instructional alignment between courses - Planning for field application protocols
Undergraduate stage	April–August 2022	Agricultural Engineering undergraduate students (Edaphology course)	- Engagement with San Cayetano farmers - Pilot field setup and soil sampling - Crop planting and monitoring under three treatments - Soil and water quality analysis (INIAP and UTPL) - Fertilization plan design and poster preparation
Community outreach and closure stage	August 2022	Undergraduate students and local stakeholders	- Dissemination of results in a participatory workshop - Technical presentations and discussion with farmers - Distribution of fertilization plans and feedback collection

summarizes the chronological progression and key milestones of each implementation phase, highlighting the interdisciplinary interactions among students, faculty, and local stakeholders.

2.4. Project Evaluation

This stage involved a systematic, multi-method evaluation of the project’s effectiveness and impact, as outlined in the planning matrix. Both academic performance and community engagement were assessed through a combination of formative and summative evaluations, direct faculty observations, focus group discussions, and a tailored student satisfaction survey adapted from validated educational instruments.

2.4.1. Formative and Summative Assessments

Student performance in both the Catalysis and Edaphology courses was evaluated based on the intended learning outcomes of the Project-Based Learning (PBL) methodology. The project began with the pretreatment of raw zeolite, followed by granulometric classification into powdered and granulated forms. These materials underwent adsorption experiments to assess their capacity to remove phosphate and ammonium from treated urban wastewater, thereby identifying the most effective particle size for nutrient recovery. Each student group synthesized approximately three kilograms of modified zeolite, with the adsorption capacity of each batch meticulously recorded, thus overcoming typical small-scale synthesis constraints. In addition, the physicochemical properties of the synthesized materials were analyzed using X-ray fluorescence (XRF, Bruker, Billerica, MA, USA), X-ray diffraction (XRD, Bruker, Karlsruhe, Germany), and Fourier-transform infrared spectroscopy (FTIR, Jasco 4100, Easton, MD, USA) to identify structural modifications and underlying adsorption mechanisms. A regeneration study was also performed to assess the reversibility of phosphate and ammonium adsorption, providing insights into the material’s potential reusability. As a final deliverable, each group submitted a detailed technical report documenting the synthesis process, adsorption outcomes, material characterization, and proposed agricultural application of the nutrient-enriched zeolites.

The evaluation framework followed the university’s established model, which includes three core learning modalities: faculty-guided learning, experiential practical learning, and autonomous learning. Each modality comprised specific activities with predefined weightings contributing to the final course grade (total of 10 points), distributed as follows:

Learning through faculty contact (35%):

Case study report (20%): At the beginning of the course, students analyzed published case studies or simulated scenarios related to nutrient recovery technologies, particularly within the San Cayetano community. This task strengthened their ability to apply catalytic principles to real-world environmental challenges.

Discussion forum participation (15%): Students led and contributed to thematic forums discussing the efficiency of various adsorbent materials and design parameters of zeolites for nutrient recovery. This activity promoted scientific communication and critical thinking.

Experimental/practical learning (30%):

Laboratory workshops (15%): Students conducted sessions involving material pretreatment, synthesis of metal oxy(hydroxides)-modified zeolites, ion-exchange reactions, and physicochemical characterization. The activities emphasized the connection between experimental procedures and applications in water treatment and sustainable fertilization, fostering technical autonomy.

Laboratory practical exercise (15%): Students compared phosphate adsorption capacities of powdered versus granulated metal-modified zeolites. A final experiment using real urban wastewater assessed the practical effectiveness of these materials, reinforcing data interpretation and technical skills.

Autonomous Learning (35%):

Laboratory report (10%): Students submitted detailed written reports describing their experimental work, highlighting reproducibility, encountered issues, and data analysis. This task strengthened their scientific writing and reporting abilities.

Demonstrative project presentation (15%): Each group presented their nutrient-recovery system orally, demonstrating understanding of adsorption results and system operation. This activity was designed to enhance innovation skills, communication, and project design.

Final written evaluation (10%): Although not directly tied to fieldwork, this exam assessed students’ foundational knowledge of catalysis, adsorption mechanisms, and their applications in environmental remediation and nutrient recovery.

A standardized grading rubric was used by faculty mentors across all evaluation components to ensure consistency, objectivity, and fairness (see

Table 3. Evaluation rubric—Catalysis course project.

Criteria	Excellent (10–9)	Good (8–7)	Satisfactory (6–5)	Needs Improvement (<5)
1. Understanding of the problem and alignment with objectives (15%)	Demonstrate a clear and thorough understanding of the problem, fully aligned with project objectives.	Shows good understanding; objectives are mostly aligned.	Demonstrates a basic understanding; objectives are vaguely addressed.	Limited or poor understanding; objectives are unclear or missing.
2. Experimental execution (20%)	Applies a well-structured, innovative methodology with accurate execution.	Sound methodological design with only minor issues.	Lacks depth; execution is inconsistent.	Methodology is flawed or incomplete; major execution errors present.
3. Data analysis and interpretation (15%)	Analysis is comprehensive; conclusions are well-supported by data.	Analysis is adequate; conclusions are generally supported.	Basic or limited analysis; conclusions are weak or tentative.	Analysis is missing or incorrect; conclusions are unsupported.
4. Real-world application (15%)	Strong connection to environmental or agricultural applications.	Good understanding of practical relevance.	Limited connection to real-world context.	No demonstrated relevance or applicability.
5. Collaboration and interdisciplinary work (10%)	Actively contributes; demonstrates strong teamwork and collaboration across disciplines.	Participates effectively in group work.	Contribution is minimal; weak collaboration.	No evidence of collaboration or interdisciplinary engagement
6. Communication skills (written and oral) (10%)	Communicate ideas clearly and effectively through well-structured reports and presentations.	Communication is generally clear and coherent.	Communication is occasionally unclear or disorganized.	Communication lacks clarity and organization.
7. Reflection and critical thinking (10%)	Provided thoughtful, in-depth reflection on challenges, results, and learning outcomes.	Provides an adequate level of reflection.	Reflection is superficial or limited.	No meaningful reflection is evident.
8. Knowledge transfer and societal relevance	Effectively contextualizes scientific knowledge within community or societal needs.	Demonstrate some awareness of broader impact.	Relevance is briefly mentioned without depth.	No indication of societal or practical application.

).

In the Edaphology course, undergraduate Agricultural Engineering students participated in the implementation phase of the nutrient recovery project by applying modified zeolites to community field plots to evaluate their effects on soil quality. Students engaged directly with local farmers, with each group assigned to a specific farm. Student performance was assessed using a rubric-based framework focused on three core learning components:

Learning through faculty contact (35%):

Midterm and bimonthly evaluations measured students’ comprehension, analytical thinking, and ability to apply theoretical knowledge. Assessment included multiple-choice and essay questions covering key topics such as soil genesis, physicochemical properties, degradation processes, and soil management. These evaluations were administered through the institutional platform under supervised virtual conditions, with real-time guidance and clarification provided by the faculty mentor.

Experimental/practical learning (30%):

This component was carried out through active participation in the outreach project, combining fieldwork, laboratory analysis, and classroom instruction. Students were organized into teams of five, each assigned to a participating farm. Initial soil samples were collected to establish baseline fertility conditions, followed by repeat sampling after three months to assess treatment effects. Pilot plots were established in San Cayetano under three treatment conditions: (i) fertilizer and zeolite, (ii) zeolite only, and (iii) control (no amendment). Students collected agronomic data, including plant count, height, leaf number, and biomass, depending on the crop type (e.g., tree tomatoes, grasses, home gardens, and vegetables). Data were compiled in Excel spreadsheets for subsequent analysis. Biweekly visits were conducted to monitor agronomic indicators. Soil samples were analyzed at the National Institute of Agricultural Research of Ecuador (INIAP) for parameters such as texture, pH, organic matter, nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, zinc, copper, iron, manganese, and boron. Additional laboratory analyses were performed at UTPL. Each student group also carried out basic soil characterization (e.g., pH, bulk density, color, and carbon stock estimation), selecting and interpreting parameters relevant to their assigned crop. Parameters assessed included pH, sulfates, dissolved oxygen, saturation, phosphates, nitrites, boron, iron, copper, lead, manganese, zinc, aluminum, nickel, selenium, vanadium, and potassium. These data provided the technical basis for customized fertilization plans, which were discussed with farmers during site visits and formally presented at the final community workshop through technical posters, reinforcing knowledge transfer. Based on soil analyses and crop nutrient requirements, students developed fertilization plans. They prepared technical posters summarizing findings and recommendations, and managed logistical tasks such as preparing registration sheets, coordinating fertilizer distribution, and printing fertilization plans for each farmer. Evaluation of this component was guided by the rubric described in

Table 4. Evaluation rubric—Edaphology course project.

Criteria	Advanced (10–9)	Intermediate (8–6)	Basic (<5)
Field and laboratory work (30%)	Participated in more than 90% of scheduled activities.	Participated in approximately 50% of activities.	Participated in less than 50% of activities.
Organization and content development—PowerPoint presentation (10%)	Presentation is clear, focused, detailed, and didactic.	Presentation partially supports the central idea; some details are missing	Presentation lacks clarity and organization; key ideas are unclear.
Topic mastery (explains, discusses, details, exemplifies, argues) (20%)	Demonstrates deep understanding with clear explanations and appropriate references.	Shows moderate understanding with general explanations.	Demonstrates limited understanding; explanations are superficial or unclear.
Responses to questions (40%)	Provides accurate, complete, and well-articulated responses.	Responses are generally adequate and correct.	Responses are vague, limited, or incorrect.

This rubric contributes 35% to the final grade.

.

Autonomous learning (30%):

This component was designed to foster individual responsibility and reinforce both theoretical and practical skills. The first activity involved the critical review of three selected scientific articles covering topics such as soil conservation, analytical techniques, zeolite application in agriculture, and fertilization planning. Each student was evaluated based on their understanding of one article, which was randomly assigned.

The second activity focused on the submission and quality of weekly assignments. These tasks were closely aligned with class topics and project-related activities, aiming to encourage knowledge integration, strengthen scientific writing skills, and promote analytical thinking.

2.4.2. Community Feedback

To evaluate the community’s perception of the project and its relevance to local agricultural practices, qualitative data were collected through structured focus group discussions with participating farmers and community members. These sessions were conducted during the final dissemination workshop held at the community center, following the application of zeolite-based treatments in the demonstration plots. The primary objective was to gather stakeholder perspectives on the effectiveness of the modified zeolite in improving soil quality, enhancing crop productivity, and contributing to sustainable farming practices.

Each focus group was facilitated by faculty members and supported by student moderators, who guided the discussion using a semi-structured question guide. Key topics included the perceived benefits of the zeolite intervention, challenges encountered during field implementation, and the potential for long-term adoption of the technology. Feedback was documented through detailed observational notes, direct quotations, and photographic records of community engagement activities, including practical demonstrations and poster presentations.

This qualitative approach allowed for a comprehensive assessment of the project’s social and practical impact, ensuring that the voices and experiences of local beneficiaries were incorporated into the overall evaluation of the initiative’s effectiveness and scalability.

2.4.3. Student Satisfaction Survey

To assess Agricultural Engineering students’ perceptions of the integrated PBL–CBL experience, a tailored questionnaire was developed (Section S2. Survey instrument validation). The instrument was adapted from previously validated educational research tools and refined to reflect the interdisciplinary and community-based nature of the project [50,51,52,53,54]. The final version of the survey comprised five multiple-choice questions and was validated by a panel of 17 academic experts. The Content Validity Index (CVI) was calculated at 0.8980, indicating excellent validity (values ≥ 0.78 are considered excellent) [65]. Similarly, the Content Validity Coefficient (CVC) was 0.8974, confirming the instrument’s reliability (CVC > 0.9 is considered excellent) [66]. Additional details of the validation process [67] are provided in the Supplementary Materials section (Section S2. Survey instrument validation). The survey was administered online at the conclusion of the project, and responses were collected in both quantitative (closed-ended) and qualitative (open-ended) formats to provide a comprehensive understanding of the student experiences and areas for improvement.

2.4.4. Data Analysis

Quantitative data obtained from the summative assessments and student satisfaction survey were analyzed using statistical methods to identify trends and evaluate learning outcomes. Qualitative data collected from focus group discussions and observational records were thematically analyzed to extract deeper insights into student learning experiences and community impact. The combined results from all evaluation components were synthesized to inform recommendations for strengthening future PBL–CBL initiatives and academic–community partnerships.

An analysis of variance (ANOVA) was performed on the final grades from different academic terms (2020–2024) to determine whether statistically significant differences existed (p < 0.05). This comparison was feasible for the Edaphology course, as it had been delivered across multiple cohorts under similar academic conditions. Duncan’s multiple range test was subsequently applied to identify specific group differences. In contrast, no longitudinal comparison was conducted for the Catalysis course, as it was implemented for the first time during the 2021–2022 academic term. Therefore, only descriptive and performance-based evaluations were considered for this course.

For the student survey responses, descriptive statistics were used to examine response patterns. A chi-square test was conducted to assess whether the observed frequency distributions significantly deviated from a uniform distribution for each question. All statistical analyses were performed using GraphPad Prism 5 software (GraphPad Software, San Diego, CA, USA), with a significance level set at p < 0.05.

3. Results and Discussion

The integration of postgraduate and undergraduate efforts in this project was achieved through a dual-level Project-Based and Community-Based Learning (PBL–CBL) framework. Figure 1 illustrates the conceptual structure of this approach, highlighting the sequential and functional roles of master’s students (responsible for zeolite synthesis and characterization), undergraduate students (responsible for field application and crop monitoring), faculty coordinators, and community stakeholders. This representation contextualizes the interdisciplinary workflow and underscores the bidirectional exchange of knowledge between academia and the rural community.

3.1. Student Competency Development

3.1.1. Outcomes from Formative and Final Evaluations

Competency Development in the Catalysis Course

Master’s students enrolled in the Catalysis course were responsible for the synthesis, physicochemical modification, and laboratory evaluation of the zeolitic materials used in the project. Their work began with the alkaline activation and ion-exchange modification of the natural precursor to produce Fe–Mn–Zn-enriched zeolites, followed by advanced instrumental characterization using X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy (SEM–EDS), and Brunauer–Emmett–Teller (BET) surface area analysis. The modification process led to a substantial increase in surface area, from 65.56 m²/g in the raw material to 136.17 m²/g in the final product, reflecting successful enhancement of porosity and surface reactivity.

These zeolites were subsequently applied in batch-mode wastewater treatment experiments to assess nutrient recovery capacity. Students evaluated both granular and powdered forms, achieving removal efficiencies of up to 72.3% for ammonium and 49.2% for total phosphorus. Controlled nutrient release tests were also conducted under simulated field conditions using soil–zeolite mixtures. Phosphate release reached up to 2.15 mg/L, while ammonium concentrations (~0.03 mg/L) were sustained over time, confirming the dual role of the material as both adsorbent and slow-release fertilizer.

Beyond technical mastery, the practical application of catalytic materials within an interdisciplinary and community-based framework strengthened students’ competencies in experimental design, sustainability assessment, and scientific communication. Their work culminated in detailed project reports, laboratory notebooks, and oral presentations, which were evaluated through both formative and summative assessments. These outputs demonstrated not only proficiency in instrumental and analytical methods but also an understanding of real-world applicability and environmental relevance.

The integration of this technical component into the broader project ecosystem provided students with a unique opportunity to transition from laboratory innovation to social impact. By bridging advanced material development with field application, the course fostered a holistic approach to catalysis education, aligned with sustainability objectives and the principles of responsible science and engineering.

The Catalysis course, part of the master’s program in Applied Chemistry and delivered during the October 2021–February 2022 term, was designed to evaluate a broad range of competencies, including theoretical knowledge, laboratory execution, critical thinking, and independent learning.

Table 5. Average grades for the Catalysis course.

Assessment Component	Weight (%)	Average Score
Case study report	20	9.42
Discussion forums	15	8.63
Laboratory workshops	15	9.30
Practical laboratory exercise	15	9.00
Laboratory report	10	8.67
Demonstrative project submission	15	7.83
Final written evaluation	10	8.78
Overall	100	8.82

summarizes the average scores obtained across various assessment components. Overall, student performance was strong, indicating the effectiveness of the integrated Project-Based Learning (PBL) methodology.

The highest average was obtained in the case study report, reflecting students’ ability to integrate theoretical concepts with real-world catalytic applications. This outcome highlights the strength of the PBL approach in promoting critical thinking and contextual problem-solving, as students were required to synthesize scientific literature, chemical principles, and applied reasoning. Discussion forum participation yielded solid results, showcasing active engagement in asynchronous academic discussion and reinforcing the value of reflective learning and collaborative knowledge-building in interdisciplinary environments. Performance in the laboratory workshops was particularly strong, demonstrating the effectiveness of structured technical training in catalyst synthesis and characterization. These activities, carried out under academic supervision, reinforced procedural accuracy and technical confidence. Similarly, the practical laboratory exercise confirmed that students could independently apply experimental protocols to address specific challenges, successfully bridging theory and practice. The laboratory report component, while showing solid results, revealed opportunities for improvement in scientific writing and data interpretation. This may reflect difficulties in translating experimental findings into coherent technical narratives. The lowest average was observed in the demonstrative project submission, where students presented their practical implementation of a nutrient recovery system. This outcome may reflect the complexities of interdisciplinary coordination, real-world constraints (e.g., material availability and external collaboration), and the transition from controlled laboratory environments to field-based applications. These findings suggest a need for additional support in project planning, interdisciplinary communication, and real-world execution. Finally, the results from the final written evaluation confirmed that theoretical learning was preserved despite the active learning approach, reinforcing that PBL supports both academic rigor and experiential learning. Taken together, these outcomes highlight the effectiveness of the PBL methodology in fostering both technical and transversal competencies. The strong performance in applied and theoretical components reflects a comprehensive learning process, while the lower scores in project submissions underscore the need to reinforce planning, execution, and interdisciplinary integration within the curriculum.

Competency Development in the Edaphology Course

Undergraduate students in the Edaphology course worked directly with the nutrient-enriched zeolite materials previously synthesized and characterized by their Chemistry peers. Their tasks encompassed the full agricultural implementation process, beginning with soil sampling and analysis to establish baseline fertility parameters. Based on these diagnostics, students developed customized fertilization plans that incorporated the zeolitic material as a slow-release nutrient carrier.

The implementation phase involved preparing experimental plots, applying the zeolite-amended fertilizers, and conducting sowing trials with selected test crops. Throughout the growing cycle, students monitored plant growth, soil conditions, and nutrient retention or release using standard agronomic indicators. This process required consistent fieldwork, iterative observation, and systematic data recording over several weeks, enabling students to connect theoretical knowledge with practical outcomes. Technical observations were complemented by reflective exercises emphasizing the environmental, social, and economic implications of using low-cost, recovered materials in sustainable agriculture.

Student performance demonstrated significant improvement in applied agronomy skills, critical thinking, and the ability to communicate scientific results in a real-world context. This was evident in the quality of their final project reports and presentations, which reflected a strong integration of scientific reasoning, sustainability literacy, and community engagement. The interdisciplinary link, although sequential, provided valuable cross-learning by requiring Agricultural students to understand, trust, and build upon the technical results generated by their Chemistry counterparts.

All students enrolled in the Edaphology course achieved a final individual average above 7.5/10, as shown in

Table 6. Average grades for the Edaphology course.

Assessment Component		Weight (%)	Average Score
Learning through faculty contact		35	8.54
Practical—experimental learning		35	8.91
	Fieldwork	5	9.60
	Laboratory work	5	8.20
	Community workshop (closing session)	25	8.92
Autonomous learning		30	9.03
	Extracurricular tasks	20	9.25
	Scientific article review	10	8.60
	Overall	100	8.60

. A detailed breakdown revealed that 54.17% of students scored 9 or higher, 29.17% obtained grades between 8.0 and 8.9, and 16.67% were in the 7.5 to 7.9 range. The latter group suggests an opportunity for pedagogical improvement. Notably, no student required remediation or makeup assessments, suggesting widespread competency achievement.

These results show strong performance across both structured academic activities and autonomous learning tasks. Notably, the high scores in the community-based learning component (closing workshop) and extracurricular tasks reflect the successful integration of theoretical knowledge with applied fieldwork.

The outcomes demonstrate well-rounded acquisition of both disciplinary and transversal competencies among undergraduate students in the Edaphology course. The strong performance in the practical–experimental learning component, specifically fieldwork and laboratory activities, demonstrates the effectiveness of the PBL–CBL methodology in reinforcing technical competencies such as soil sampling, nutrient analysis, and the application of zeolite-based treatments in authentic agricultural contexts. The high scores in fieldwork reflect students’ ability to engage with real agronomic challenges, manage environmental variability, and apply soil fertility and nutrient management concepts to practical experimentation.

Likewise, strong performance in autonomous learning, particularly in extracurricular tasks, indicates students’ active commitment to consolidating knowledge beyond the classroom. These tasks include preparing fertilization plans and analyzing field data, which fostered critical thinking, technical reporting, and professional agricultural skills.

The outstanding results in the community-based component demonstrate student proficiency in science communication, stakeholder engagement, and teamwork. Through dissemination sessions and farmer-specific fertilization plans, students translated technical concepts into accessible formats, strengthening academic–community interaction. This experience not only enhanced their social competencies, civic responsibility, and sustainability-oriented thinking, but also cultivated key attributes required in modern agricultural education.

Taken together, these findings confirm that the integrative approach of the Edaphology course effectively developed comprehensive student competencies. The balance between classroom learning, field practice, independent study, and community interaction is clearly reflected in the strong overall performance. These results further validate the relevance and applicability of PBL–CBL methodologies in undergraduate agricultural training, especially when aligned with real-world problems and interdisciplinary collaboration.

Additional statistical analysis revealed significant differences across academic terms, with the April–August 2022 cohort, when the research project was implemented, showing the highest mean scores and the lowest standard deviation (

Table 7. Mean and standard deviation of grades across academic terms in the Edaphology course.

Term	Number of Students	Mean ± SD	Significant Difference
April–August 2020	10	7.48 ± 2.36	a
April–August 2021	22	7.59 ± 1.57	a
April–August 2022 *	24	8.84 ± 0.69	b
April–August 2023	13	7.65 ± 2.03	a
April–August 2024	22	7.07 ± 1.29	a

Letters a and b indicate statistically significant differences between groups according to Duncan’s post hoc test (p < 0.05). * Period during which the research was conducted.

). This indicates not only elevated performance but also greater consistency among students during that term.

Table 8. Comparative summary of competency development outcomes across postgraduate (Catalysis course) and undergraduate (Edaphology course) cohorts.

Dimension	Postgraduate (Catalysis Course)	Undergraduate (Edaphology Course)
Technical competencies	Advanced laboratory synthesis, zeolite modification, instrumental analysis (XRD, XRF, SEM–EDS, BET); adsorption/release experiments	Field-based agronomic monitoring, soil and crop analysis, fertilization plans
Research and problem-solving	Experimental design, sustainability assessment, critical data interpretation	Adaptive problem-solving in agricultural contexts, integration of soil diagnostics with crop needs
Communication	Scientific reporting (technical reports, lab notebooks), oral presentations, and formative and summative evaluation	Engagement with farmers, preparation of posters, participatory workshops, and presentation of fertilization plans
Professional and transversal skills	Critical thinking, systems perspective, independent learning, responsibility in material development	Teamwork, rural extension practices, empathy, and contextual understanding of sustainability
Community engagement	Indirect (materials delivered to Agricultural cohort for field use)	Direct interaction with local farmers, feedback collection, and participatory validation of results

provides a comparative summary of competency development outcomes across postgraduate and undergraduate cohorts, complementing the detailed results shown in Table 5 and Table 6. This synthesis highlights the differentiated yet complementary learning gains fostered through the integrated PBL–CBL framework.

3.1.2. Comparative Analysis and Pedagogical Reflections

The dual-level structure of the project, integrating postgraduate and undergraduate students through complementary academic modules, enabled differentiated yet synergistic competency development. Master’s students in the Catalysis course demonstrated significant gains in laboratory-based competencies, particularly in instrumental analysis, materials synthesis, and interpretation of adsorption behavior. These improvements are directly attributable to the research-centered instructional model, which emphasized experimental design, autonomous operation of analytical equipment, and scientific reporting. The instructional strategy fostered graduate-level cognitive engagement through scaffolded formative evaluations and alignment with real-world sustainability goals, such as nutrient recovery and circular resource use.

In contrast, undergraduate students in the Edaphology course exhibited greater improvement in field-based and interpersonal competencies. Their engagement with real agricultural systems, ranging from soil sampling and fertilization planning to crop monitoring and participatory farmer workshops, strengthened skills in communication, extension, and adaptive problem-solving. The instructional model, grounded in Community-Based Learning (CBL), emphasized experiential scaffolding, team-based implementation, and iterative interaction with stakeholders. As a result, students developed a strong sense of professional responsibility and a contextualized understanding of sustainable agriculture.

This contrast in competency development reflects intentional instructional differentiation. Rather than applying a uniform curriculum, the project adopted a distributed expertise model, whereby each student group contributed according to its disciplinary strengths and course learning outcomes. While this facilitated effective collaboration, it also revealed structural limitations, such as asynchronous calendars, that constrained real-time interdisciplinary co-learning.

Nonetheless, the integration of Project-Based Learning (PBL) and CBL methodologies effectively fostered key competencies across both cohorts. By aligning technical tasks with community challenges and embedding academic content within applied scenarios, the instructional design not only improved student performance but also enhanced the educational relevance and social impact of the project.

3.2. Student Satisfaction and Perceptions

Of the 24 students enrolled in the Edaphology course, 19 (n = 19) completed the post-project satisfaction survey, offering valuable insights into their learning outcomes, motivation, and overall experience. All respondents were Agricultural Engineering students between the ages of 20 and 23. The results revealed that approximately 61% of students (Figure 2A) identified limited community support as one of the main challenges faced during the implementation of the outreach project in the rural community of San Cayetano. Regarding skills development, teamwork was reported as the most improved competency (31%), closely followed by communication with the community (28%) (Figure 2B). In terms of perceived benefits, 29% of students highlighted the improvement of technical competencies, while another 29% emphasized the practical application of theoretical knowledge (Figure 2C). These results suggest that community-engaged projects not only contribute to addressing local issues but also foster the acquisition of key transferable skills such as collaboration, stakeholder communication, adaptability, and the contextualization of academic content. Moreover, 34% of respondents indicated that stronger community involvement is essential for the success of future outreach initiatives (Figure 2D), underscoring the importance of promoting active community participation from the early planning stages. This view was further supported by open-ended responses, which reflected a critical and constructive perspective from students regarding project design and implementation. Notably, 89% of students (Figure 2E) recommended incorporating more community-based projects into the academic curriculum, recognizing their value in reinforcing learning through real-world application.

A chi-square test yielded a value of 18.2 with three degrees of freedom, corresponding to a p-value < 0.001. Since this value falls well below the conventional significance threshold of 0.05, the null hypothesis of uniform distribution across the response categories was rejected. This indicates statistically significant variation in students’ preferences and perceptions across the survey dimensions.

In general, students’ open-ended responses reflected highly positive perceptions of the experience. One of the most frequently praised aspects was the strengthening of interpersonal relationships within the academic context. As one student remarked: “This helps to build better relationships with teachers and classmates”, highlighting improvements in classroom dynamics and fostering a more collaborative learning environment, essential elements in effective teaching and learning. Another student stated, “It helps to apply the knowledge acquired and to connect with society”, emphasizing alignment of the project with one of the university’s strategic goals: community engagement and contribution to solving local challenges. This form of experiential learning not only consolidates theoretical course content but also cultivates students’ sense of social responsibility as future professionals.

Similarly, one student noted that the experience “allows the development of more projects and gaining more experience for the future,” stressing the importance of providing opportunities that connect academic training with professional development. The skills and confidence gained through such community-focused projects are seen by students as valuable resources in preparing for real-world demands.

To enrich qualitative analysis, representative student quotes were integrated to illustrate their reflections on the learning experience. Undergraduate students consistently emphasized the value of applying theoretical knowledge in real-world contexts. One student remarked: “This project helped us apply what we learned in class and interact meaningfully with the community,” highlighting the transition from passive content reception to active, situated learning.

Others focused on the development of specific competencies, particularly in communication and rural outreach: “For Agricultural Engineering, it strengthened our understanding of rural extension practices and improved our ability to communicate with local farmers.” This response demonstrates how the project context fostered dialogical engagement, a key feature of constructivist learning environments.

The integration of classroom learning with practical fieldwork was frequently cited as a transformative component of the experience. As one student noted: “It complemented our studies by adding hands-on experience, which prepares us better for future projects.” This reflects a growing sense of professional preparedness, one of the core objectives of competency-based education models.

Another participant highlighted broader interpersonal and metacognitive outcomes: “It’s important to practice what we are taught in class so we can explain it to others. This also improves our relationships with instructors and classmates.” This statement underscores the dual value of PBL–CBL frameworks, not only in terms of technical knowledge acquisition but also in fostering confidence, empathy, and collaborative learning skills.

Taken together, these insights reinforce the effectiveness of combining Project-Based and Community-Based Learning approaches in fostering holistic student development. They also support the argument that community-engaged education serves not only academic objectives but also strengthens students’ civic responsibility and personal growth.

3.3. Community Engagement Feedback

3.3.1. Focus Group Themes

The thematic analysis of two focus groups involving 20 participating farmers revealed key insights into the community’s experience and perception of the outreach project. Feedback was collected systematically through semi-structured interviews and interactive sessions facilitated using participatory rural appraisal tools. These methods ensured the inclusion of diverse viewpoints and promoted open, collaborative dialog. A community representative and leader of the first group emphasized the agricultural potential of the area, stating, “The place lends itself to agricultural spaces.” This observation underscores the importance of aligning land-use strategies with the region’s physical and socio-environmental characteristics. It also reflects the community’s awareness of the need to preserve productive zones for agriculture while balancing residential development.

Another participant expressed a strong sense of ownership and responsibility regarding the project, stating, “There must be a counterpart; not everything has to be provided by the University, residents are committed to moving the project forward”. This testimony illustrates a fundamental principle of sustainable development: shared responsibility between academia and local stakeholders. The community’s willingness to act as co-creators, rather than passive beneficiaries, reinforces the feasibility and relevance of long-term collaborative initiatives. During the closing community workshop, an event held to disseminate project outcomes, a notable multiplier effect was observed. Verbal communication among attendees sparked growing interest from new community members, especially after the presentation of promising preliminary results. This peer-to-peer dynamic highlights the scalability of university-led projects in rural agricultural settings, particularly when outcomes are tangible and shared in accessible formats.

In addition to the perspective of the community leader, several farmers provided insights that highlight the perceived utility and relevance of the zeolite-based materials. One participant remarked, “We noticed the plants were greener and stronger in the plots where the powder was used. It didn’t burn the soil like some fertilizers,” emphasizing both efficacy and safety. Others appreciated the environmental and economic potential, as noted in the comment, “If this material is made from rocks and doesn’t harm the environment, I think it’s better than buying chemicals every month.” Practical field benefits were also noted: “It helped keep the moisture in the soil longer, especially during the dry days.”

Beyond agronomic performance, farmers emphasized the educational dimension of the collaboration: “At first, we didn’t understand what the material was, but after the students explained it, we saw the results and now we trust it.” This feedback validates the importance of clear science communication and sustained engagement, which was further reinforced by another statement: “The students came more than once, they followed up. That’s something we appreciate.” Collectively, these voices highlight both the pedagogical and technical effectiveness of the project, underscoring a strong foundation for future participatory research and technology transfer.

3.3.2. Recommendations for Wider Implementation

Despite the project’s initially limited scope, participants expressed strong enthusiasm and advocated for its continuation with broader inclusion. Specific suggestions included expanding the number of beneficiary households and improving dissemination materials. Participants recommended the development of practical educational resources, such as short video tutorials or illustrated brochures, to support farmers with varying levels of technical expertise. Additionally, farmers proposed establishing long-term institutional partnerships to enhance the project’s continuity and impact. These recommendations underscore the importance of designing outreach initiatives that combine technical depth with accessible communication strategies to promote meaningful and sustained adoption in rural areas. Findings from these focus groups confirm that integrating students into community-centered, problem-based learning (PBL) initiatives not only enriches their academic formation but also generates socially relevant, tangible outcomes for local stakeholders. The community’s positive reception further highlights the mutual benefits of linking higher education to real-world problem-solving in agricultural development contexts.

Follow-up observations conducted two months after project completion provided preliminary insights into community satisfaction and engagement. Several farmers who participated in the field trials reported visible improvements in soil condition and early crop development when using the zeolite-amended substrate. Their positive perception of the material’s agronomic performance suggests initial acceptance of the proposed innovation. These findings represent evidence-based observations that provide short-term validation of the intervention.

In contrast, the long-term sustainability of the initiative remains constrained by logistical and operational factors. In particular, the continuity of zeolite material production depends on the availability of trained personnel and laboratory infrastructure, which currently reside within the university. This limits both the frequency and scalability of future applications. Furthermore, transitioning the initiative toward a broader and more sustainable framework will require institutional support beyond academia.

Integrating the zeolite production process into the city’s wastewater treatment plant (PTAR) represents a strategic opportunity to ensure a stable material supply, valorize local residues, and align with circular economy principles. Such proposals constitute forward-looking recommendations intended to guide long-term sustainability and scalability. This model, however, requires coordination with municipal authorities and governmental agencies, stakeholders not currently engaged in the pilot project. While the university and community have demonstrated strong initial commitment, a broader multi-sectoral partnership will be essential for long-term implementation, scaling, and policy integration. This constitutes both a limitation of the current study and an opportunity for future work.

3.4. Faculty Reflections and Observations

The interdisciplinary nature of the PBL–CBL initiative required continuous mentorship and adaptive coordination, particularly given the curricular and logistical differences between the master’s program in Applied Chemistry and the undergraduate Agricultural Engineering program. Faculty mentors from both programs provided structured guidance through formative check-ins, applied evaluation rubrics, and adjusted instructional strategies based on student and project needs.

3.4.1. Mentor Insights

Faculty mentors observed distinct patterns in student development and project execution across the two academic cohorts. Master’s students focused primarily on laboratory research, specifically the synthesis and preliminary evaluation of modified zeolite materials. Their work was conducted in small groups due to time limitations and restricted access to laboratory facilities. As a result, synthesizing enough material for field application posed a logistical challenge, requiring incremental batch production and coordination beyond regular laboratory schedules.

Notably, master’s students did not directly engage with the community until the final dissemination event. Their efforts centered on material development and experimental validation in an academic setting. In contrast, undergraduate students from the Agricultural Engineering program were responsible for field implementation. They interacted with farmers, explained the application protocol of the zeolite-based material, and managed its deployment in soil trials. This delineation of responsibilities reflected both the distinct competencies of each academic program and practical constraints related to off-campus activities.

The instructional strategies employed in this initiative were grounded in constructivist and social learning theories. Constructivism posits that learners build knowledge through experience and reflection, particularly when addressing authentic challenges. Here, students engaged in hands-on experimentation, fieldwork, and stakeholder interaction to construct meaningful understanding. Simultaneously, social learning was supported through collaborative group work, peer interaction, and exposure to community dynamics, enabling students to observe, model, and internalize professional behaviors and problem-solving approaches in real-life contexts, thereby strengthening both cognitive and interpersonal skills.

Contrary to initial expectations, students did not provide detailed scientific explanations of nutrient recovery mechanisms to farmers. This pedagogical decision stemmed from two key considerations: (i) the limited experience of Agricultural students in scientific communication, and (ii) the community’s preference for practical, actionable formation. Instead, students focused on explaining the material’s usage, timing, expected benefits, and key differences from traditional fertilizers, ensuring the communication was both relevant and understandable.

Faculty also identified several challenges during implementation. First, coordination difficulties arose due to asynchronous academic calendars and schedules between student groups. Second, infrastructure limitations for large-scale material synthesis required staggered laboratory shifts and placed additional pressure on resources. Third, initial communication insecurity among undergraduate students when engaging with community members was observed; however, this improved over time as students’ confidence increased.

To ensure equitable and context-sensitive evaluation, distinct rubrics were developed for each academic group. These rubrics reflected the specific tasks of each cohort: laboratory-based synthesis and analysis for postgraduate students, and field-based implementation and communication for undergraduates. Weekly feedback sessions, particularly with master’s students in the Catalysis course, allowed for close monitoring of progress, early identification of technical challenges, and targeted mentoring. This differentiated approach ensured alignment between evaluation, learning outcomes, and program-specific expectations, while maintaining academic transparency and rigor.

The higher academic performance observed during the implementation cycle is attributable not only to the formal content delivery but also to the motivational boost from real-world community engagement [68]. The direct connection between classroom learning and social impact fostered a greater sense of purpose and accountability. Recognizing the real-world relevance of their work led students to demonstrate greater commitment and preparedness [69]. Moreover, operating outside the traditional classroom without constant supervision fostered autonomy, organization, and decision-making skills, deepening their engagement with the learning process and encouraging initiative-driven professional development.

3.4.2. Pedagogical Adjustments

To address the dynamic needs of the project and respond to instructional challenges, several pedagogical modifications were introduced to support student learning and ensure successful project execution. First, a redistribution of workload and adjustment of the project timeline were implemented. Although the project was originally embedded solely within the Catalysis module of the master’s program, the experimental workload, particularly synthesizing sufficient quantities of modified zeolite, posed significant logistical challenges. Given that the module spanned only four weeks, students were initially organized into smaller groups to carry out batch synthesis. However, as the required production scale exceeded initial estimates, timeline extensions and workload redistribution became necessary. These adjustments allowed students to complete synthesis tasks progressively and responsibly, even outside regular laboratory hours, without compromising academic integrity.

Second, efforts were made to clarify roles and enhance instructional scaffolding. To improve coordination and reduce redundancy, clear distinctions were established between the responsibilities of each student group. Master’s students focused on synthesis and characterization in the laboratory, while Agricultural Engineering undergraduates managed material application and community engagement. This division supported discipline-specific skill development and improved execution.

Third, additional support was provided to strengthen students’ science communication and stakeholder interaction capacities. Recognizing the importance of effective knowledge transfer, undergraduate students received targeted guidance on simplifying technical content, adapting language for stakeholder contexts, and communicating confidently during fieldwork and community workshops.

These instructional refinements underscored the importance of balancing academic rigor with operational feasibility in interdisciplinary, time-constrained projects. Faculty reflections emphasized the necessity of adapting teaching strategies to program structures, supporting evolving student needs, and maintaining a strong focus on social impact within the limits of practical implementation.

3.5. Responses to Research Questions

To evaluate the educational and social impact of the interdisciplinary PBL–CBL initiative, three research questions were formulated, addressing student learning outcomes, satisfaction, and community perceptions. This section synthesizes both quantitative and qualitative findings, providing an integrated analysis of how the project influenced technical skill development, professional competencies, and engagement with local stakeholders. The results offer a comprehensive perspective on the effectiveness, challenges, and pedagogical implications of the implemented model across both academic programs and community contexts.

Research question 1: In what ways does engagement in a combined PBL–CBL initiative enhance students’ interdisciplinary technical skills and professional competencies across the Applied Chemistry and Agricultural programs?

The project successfully promoted interdisciplinary learning by integrating technical competencies with real-world applications across the Chemistry and Agricultural domains. Master’s students in the Applied Chemistry program enhanced their laboratory skills through the synthesis, characterization, and adsorption evaluation of modified zeolites. Their performance, assessed through analytical rubrics, laboratory reports, and reflective journals, demonstrated significant improvement in experimental design, analytical accuracy, and scientific communication.

In parallel, undergraduate students from the Agricultural program led the field implementation, which included evaluating soil conditions, applying the synthesized zeolitic materials, and engaging with community stakeholders. This experience fostered adaptive planning, problem-solving, and stakeholder engagement, skills essential for professional practice in agricultural sciences. Notably, survey responses revealed that students identified “community communication” and “agricultural field techniques” as the most developed competencies, reinforcing the authenticity and relevance of their learning environment.

Survey analysis also highlighted disciplinary differences in perceived skill development: Chemistry students reported stronger growth in laboratory experimentation and data interpretation, while Agricultural students emphasized competencies related to fieldwork and practical engagement. Additionally, a chi-square test revealed statistically significant differences based on the local context of intervention, suggesting that the complexity and socio-environmental dynamics of each site influenced learning outcomes, particularly in collaborative decision-making, adaptability, and conflict resolution.

Although direct interaction between both student groups was limited, their coordinated efforts toward a common objective reflected the structure of real-world interdisciplinary collaboration. The project demonstrated that integrative learning can occur not only through shared tasks but also through complementary roles that converge to produce a community-relevant outcome.

Research question 2: To what extent are students satisfied with the integrated PBL–CBL model, and which specific elements (e.g., laboratory experimentation, fieldwork collaboration, community interactions) do they identify as most impactful?

Overall, student feedback reflected high levels of satisfaction with the PBL–CBL approach, particularly valuing the opportunity to apply theoretical knowledge in authentic, real-life settings. According to the satisfaction survey, 52% of students considered the real-world application of academic concepts to be the most valuable aspect of the experience, followed by the development of both technical and interpersonal competencies. Master’s students reported that laboratory experimentation was the most impactful component, whereas Agricultural students prioritized fieldwork and direct engagement with the community.

However, the survey also revealed several challenges, the most frequently mentioned being the lack of sustained community support. This issue was especially evident during the deployment and data collection phases, where coordination with local stakeholders was crucial. These findings emphasize the importance of building strong, early partnerships with community members in PBL–CBL projects to ensure alignment and smoother execution.

Students also highlighted the value of interdisciplinary collaboration, reflective practices (e.g., journal writing), and continuous faculty mentoring. Suggested areas for improvement included better time management, greater student involvement during the planning phases, and enhanced logistical and technical support. These recommendations stress the need for a well-organized, context-aware instructional framework to maximize the educational impact of PBL–CBL projects.

These findings align with constructivist and social learning theories, which emphasize that meaningful learning occurs through active participation in authentic contexts and social interaction. Constructivism posits that learners build knowledge by linking new experiences to prior understanding, particularly when solving real-world problems. In this project, both Chemistry and Agricultural students engaged in situated learning experiences that promoted reflection, critical thinking, and interdisciplinary knowledge integration. Social learning was further demonstrated in how students learned through observation, dialog, and collaboration, not only with peers but also with community members and faculty. The combination of fieldwork, community immersion, and laboratory experimentation created a dynamic environment in which students co-constructed knowledge, shaped their professional identities, and developed a sense of purpose rooted in social impact. This alignment between pedagogical design and human-centered outcomes strengthens the validity and replicability of the implemented PBL–CBL model.

Research question 3: How do participating farmers, via focus-group feedback, evaluate the relevance, practicality, and perceived benefits of the student-developed nutrient-recovery zeolite in their sustainable agricultural practices?

Focus group feedback indicated that local farmers found the use of zeolite-based fertilizers to be both practical and highly relevant to their agricultural needs. Participants acknowledged the potential of the material to reduce reliance on conventional fertilizers, lower production costs, and improve soil quality. The slow-release properties of the material were especially appreciated, as was its compatibility with local farming practices and accessibility for small-scale producers.

Despite the positive reception, farmers expressed concern regarding the availability of the material at scale and stressed the need for additional training and demonstrations. They suggested the development of practical educational resources, such as video tutorials or illustrated guides, to support broader adoption, particularly for farmers with limited technical experience. They also emphasized the importance of continued university support and the establishment of long-term partnerships to ensure the initiative’s sustainability.

Although the farmers did not engage directly with the scientific mechanisms underlying the technology, their willingness to adopt and promote the material reflects strong alignment between the project outcomes and the practical needs of the local agricultural community. This feedback underscores the value of student-led interventions grounded in participatory methods and highlights the potential of academic-community collaboration in advancing sustainable agricultural solutions.

3.6. Integrated Discussion: Lessons Learned and Implications

3.6.1. Synthesis of Key Findings

This project demonstrated the pedagogical potential of integrating Project-Based Learning (PBL) and Community-Based Learning (CBL) as a framework for competency development at both postgraduate and undergraduate levels. The use of mixed methods, combining quantitative data (e.g., rubric-based evaluations, student satisfaction surveys) with qualitative inputs (e.g., reflective journals, focus group insights, and faculty observations), enabled a comprehensive analysis of student learning outcomes and overall project impact.

One of the project’s main strengths was the significant development of technical and professional competencies among students from both programs. Master’s students exhibited clear improvements in laboratory synthesis, material characterization, and data interpretation, while Agricultural Engineering undergraduates developed critical skills in community outreach, field experimentation, and science communication in applied contexts. High levels of student satisfaction were also reported, with most participants emphasizing the value of applying theoretical knowledge to real-world challenges and contributing meaningfully to socially relevant problem-solving. Additionally, the project achieved strong community recognition and engagement. Local farmers acknowledged the practical benefits and sustainability of the zeolite-based nutrient recovery materials. Although the scientific concepts were simplified for accessibility, the perceived effectiveness and observed outcomes encouraged other community members, demonstrating a “multiplier effect” through peer dissemination.

Despite these successes, the project also revealed areas for improvement. The structural separation between academic cohorts limited opportunities for interdisciplinary dialog. Future implementations could benefit from creating shared collaboration spaces to encourage integrative thinking and mutual learning. Laboratory infrastructure constraints, particularly limited access and time-sensitive synthesis protocols, restricted the scale of zeolite materials production, underscoring the importance of improved logistical planning and resource allocation. While agricultural students effectively communicated practical application guidance, their ability to convey scientific principles was limited, highlighting the need for targeted training in science communication tailored to diverse stakeholder audiences. Furthermore, given the diverse realities of rural communities, future initiatives would benefit from adopting more interdisciplinary project designs that simultaneously address social, environmental, and economic dimensions. Finally, the long-term success of such initiatives requires the definition of clear, measurable, and context-sensitive indicators to track not only immediate outcomes but also the sustainability and community impact over time.

3.6.2. Lessons Learned

This project revealed several strategies that can foster stronger interdisciplinarity in dual-level PBL–CBL frameworks. Derived from the practical implementation, these lessons provide insights into how academic design can better connect technical and pedagogical dimensions. First, the distributed expertise model, in which postgraduate and undergraduate cohorts contributed complementary competencies, proved effective in linking advanced laboratory work with practical field applications. Second, coordinated milestones between the two programs facilitated continuity across asynchronous academic calendars, although future implementations should integrate joint project checkpoints to enable more sustained dialog. Third, structured opportunities for reflection, such as joint workshops and collaborative reporting, emerged as critical for bridging disciplinary perspectives and reinforcing shared objectives. Taken together, these lessons emphasize that interdisciplinarity does not occur automatically but requires intentional design. Aligning timelines, scaffolding collaborative spaces, and valuing distributed expertise are practical strategies that can enhance the integration of technical and pedagogical dimensions in sustainability education.

3.6.3. Implications for Higher Education: Advancing PBL and CBL Frameworks

This experience underscores the effectiveness of interdisciplinary PBL–CBL models in connecting academic instruction with real-world problem-solving. The project offers a replicable approach for integrating STEM-focused undergraduate and postgraduate programs around community-oriented objectives.

The division of roles based on curricular structure allowed students to contribute meaningfully within their academic domains; however, future iterations could be enhanced by promoting greater interaction across programs. Suggested strategies include joint field visits, interdisciplinary seminars, or co-authored reports to foster deeper collaborative learning.

More broadly, the findings affirm the potential of context-based learning environments to transform STEM education by connecting it to local and socially relevant challenges. The university’s role as an agent of social innovation was evident in its capacity to mobilize academic resources toward sustainable development goals through active community engagement.

Student reflections and field experiences revealed not only technical learning but also a deeper understanding of the educational and social value of working with local producers. These interactions promoted mutual knowledge exchange, raised awareness of local socioeconomic conditions, and laid the foundation for participatory research that benefits both the university and the community [70].

Although the importance of university-community partnerships is widely acknowledged in the literature [71], their implementation continues to face structural challenges. These include increased time commitments for faculty and students, as well as additional logistical and financial demands. Furthermore, group dynamics, such as differences in learning styles [72], levels of engagement, and time management skills [73], can influence outcomes. These challenges highlight the need to intentionally foster interpersonal and collaborative skills within curricula to better prepare students for complex, real-world contexts.

3.6.4. Limitations and Future Directions

This study provides a pedagogical analysis of an interdisciplinary initiative combining Project-Based Learning (PBL) and Community-Based Learning (CBL) across postgraduate and undergraduate programs. Nonetheless, several limitations should be considered. First, the lack of simultaneous interaction between master’s students in Applied Chemistry and undergraduates in Agricultural Engineering limited opportunities for direct interdisciplinary collaboration. This was primarily due to curricular structure: master’s courses such as Catalysis are delivered intensively over one month, while undergraduate courses such as Edaphology span a full 16-week term. As a result, although both groups contributed to the same overarching project, their asynchronous involvement reduced opportunities for richer exchanges and cross-disciplinary learning. Second, the academic maturity of graduate students enabled them to assimilate and apply complex scientific concepts more effectively, whereas undergraduates would benefit from structured training in science communication to improve their ability to convey technical information to non-specialist audiences, such as community stakeholders. Third, logistical constraints in laboratory synthesis limited the scale of material production. The quantity of zeolite required for field application exceeded what could be realistically produced during the course timeline, requiring staggered batch synthesis and complicating its alignment with fieldwork. From a research standpoint, the project generated substantial data across pedagogical, scientific, and field-based dimensions. For this reason, the current manuscript focuses exclusively on educational outcomes, including student competencies, learning experiences, and community engagement. A separate, forthcoming publication will address the technical aspects in greater depth, including the physicochemical characterization of the synthesized zeolite, plant growth indicators, nutrient uptake analysis, and soil quality improvements. Future work should prioritize better coordination between cohorts through planned points of interaction, expand training in interdisciplinary teamwork and science communication training, and refine evaluation tools based on iterative feedback. Moreover, assessing the long-term adoption and sustainability of the nutrient recovery solution within the community will be critical to validate its broader impact beyond the academic setting.

3.6.5. Structural and Pedagogical Limitations in Dual-Level PBL–CBL Models

Although the project was designed to promote interdisciplinary collaboration between Chemistry and Agricultural Engineering students, the actual interaction was predominantly sequential rather than integrated. This was primarily due to the asynchronous academic calendars and differing course structures across the two programs, which hindered the alignment of shared learning activities. Consequently, Chemistry students completed material synthesis in advance, while Agricultural students subsequently applied the materials in the field, limiting opportunities for real-time co-learning or interdisciplinary dialog.

This structural separation, while effective for logistical execution, represents a missed opportunity to foster more dynamic knowledge exchange and mutual understanding across disciplines. Future iterations of the project should consider implementing joint project milestones, co-taught interdisciplinary modules, or shared reflection workshops to facilitate deeper collaboration. Such strategies could enhance not only the technical and pedagogical outcomes but also student perceptions of interdisciplinary problem-solving in sustainability contexts.

While the integration of PBL and CBL frameworks provided substantial pedagogical benefits, their implementation within a resource-constrained academic setting also revealed challenges consistent with those reported in the literature. Infrastructure limitations, particularly restricted laboratory capacity and scheduling conflicts, required iterative adjustments to synthesis timelines and coordination across cohorts. Moreover, differences in students’ prior experience with interdisciplinary teamwork and community engagement posed instructional challenges that required sustained scaffolding and adaptive faculty support.

Despite the growing body of evidence supporting Project-Based Learning (PBL) and Community-Based Learning (CBL) as effective strategies for fostering active, situated learning in higher education, critical analyses reveal that their implementation is not exempt from limitations. Integrated PBL–CBL initiatives often face structural and operational barriers that constrain scalability and long-term impact. Studies in diverse STEM contexts emphasize that, beyond their pedagogical benefits, these approaches demand substantial institutional support, logistical coordination, and faculty preparedness, resources that are not always available in resource-limited academic settings. Students also report challenges such as unequal participation, infrastructural deficits, and difficulties in sustaining cross-level or interdisciplinary projects over time, underscoring the need to treat PBL–CBL as context-dependent rather than universally applicable. Chang et al. (2024) provide empirical evidence that embedding PBL in authentic, real-world contexts significantly increases student engagement across cognitive, emotional, and behavioral dimensions, strengthening collaboration and communication while helping students translate theoretical knowledge into meaningful practice [74]. However, the authors also highlight persistent challenges such as variability in student participation and the difficulty of ensuring equitable engagement across diverse groups, noting that disengagement and “social loafing” can persist if scaffolding is insufficient. Similarly, Chien and Chien (2025) demonstrate that problem-based approaches, when integrated into ESG-centered general education courses, can foster communication, innovation competencies, and motivation through authentic sustainability tasks [75]. Yet, despite these promising outcomes, their study found that improvements in competencies such as interpersonal interaction and problem-solving were less statistically robust, reflecting the difficulty of consolidating higher-order skills within the short timeframe of a single course. Collectively, these findings highlight both the pedagogical potential of PBL–CBL and the practical constraints that must be addressed to ensure inclusive, sustainable, and scalable implementations.

3.6.6. Curricular Implications and Faculty Development

The dual-level PBL–CBL integration developed in this project highlights several curricular implications. First, it underscores the value of interdisciplinary collaboration, linking laboratory experimentation with real-world agricultural applications. Second, it emphasizes the importance of embedding practical experiences into course syllabi to promote transferable skills such as scientific communication, teamwork, and problem-solving. This approach requires faculty to evolve beyond content delivery, adopting roles as facilitators, coordinators, and mentors. Therefore, institutional support for faculty development in active learning, project design, and community liaison strategies is critical for scaling and sustaining this model.

4. Conclusions

This study highlights the educational and societal value of integrating Project-Based Learning (PBL) with Community-Based Learning (CBL) in a multidisciplinary university setting. Through collaboration between postgraduate students in Applied Chemistry and undergraduate students in Agricultural Engineering, a zeolite-based nutrient recovery material was successfully synthesized and tested under real agricultural conditions. The PBL–CBL approach proved effective in fostering technical, communication, and professional competencies across both academic programs. Postgraduate students excelled in laboratory synthesis and characterization, achieving average scores above 9.2/10 in the Catalysis course. Similarly, undergraduate students in the Edaphology course performed strongly in field application and community engagement, with an average 8.7/10. Surveys revealed that 52% of students valued the opportunity to apply theoretical knowledge in real-world contexts, while feedback from farmers highlighted the practicality and perceived benefits of the zeolite material, particularly its slow-release behavior and contribution to sustainable agriculture. The novelty of this work lies in the structured integration of interdisciplinary academic programs toward a shared, community-linked objective. The modular project design, adapted to different academic contexts, proved scalable, replicable, and transferable to other STEM education settings. Supported by both qualitative (reflective journals, focus groups) and quantitative evidence (rubric-based evaluations, chi-square tests), this pedagogical model demonstrates how higher education can foster critical thinking, systems understanding, and civic responsibility while advancing sustainable agricultural practices. Aligned with SDG 4 (Quality education) and SDG 12 (Responsible consumption and production), the initiative highlights the role of academia–community collaboration in promoting transformative learning and sustainable development. Future research will assess the agronomic performance and long-term adoption of the zeolite material, extending the impact of this dual-level educational framework beyond its current pedagogical scope.