Life Cycle Assessment and Exergetic Performance of Solar Agricultural Dryers: Scientific Trends, Technological Niches, and Transitions Toward Sustainable Postharvest Systems

Life Cycle Assessment (LCA) applied to solar agricultural drying technologies has become a critical research area for quantifying postharvest sustainability and informing climate mitigation policies. Based on 42 documents indexed in Scopus (1999–2025), this bibliometric study integrates keyword co-occurrence (VOSviewer) and strategic thematic mapping (Bibliometrix) to identify research evolution, conceptual cores, and emerging opportunities in this field. Scientific production has intensified since 2020, with a 300% increase, driven by Asia (India 43%, followed by Bangladesh, China, and Egypt) and an emerging presence in the Americas and Europe. Results indicate increasing convergence among energy efficiency, environmental impact, and economic feasibility, with 4E approaches (Energy–Exergy–Environment–Economics) becoming the prevailing framework for comprehensive system evaluation. The co-occurrence network reveals four technological domains: (i) exergetic efficiency and thermal energy storage (heat storage, PCM, phase change materials), (ii) environmental analysis and carbon footprint (LCA, carbon dioxide, environmental impact), (iii) energy hybridization (hybrid solar–biomass dryers, photovoltaic/thermal systems), and (iv) agro-industrial applications (fruits, vegetables, high-value crops). The thematic map positions the solar dryers–environmental impact–drying cluster as the motor theme of current research, while life cycle–biogas–carbon dioxide constitutes an emerging niche associated with advanced environmental modeling. The scientific trend points toward multicriteria design and digitalization of solar drying systems, integrating LCA, thermoeconomics, and exergy analysis to optimize materials, geometry, and thermal flow behavior. Future research must strengthen dynamic and comparative LCA methodologies, AI-assisted control and adaptive optimization, and circular models of energy and material flow that transform agricultural drying into a low-carbon, measurable, and environmentally restorative process aligned with the goals of sustainable food systems and renewable energy transitions.