Environmental Performance of Circular Cascade Hydroponic Systems: A PEFCR-Based Comparative Life Cycle Assessment of Greenhouse Cucumber and Melon Production

Conventional hydroponic systems, although resource-efficient, face significant sustainability challenges due to the discharge of nutrient-rich effluents, resulting in severe environmental pressures. In alignment with the European Union’s “Farm to Fork” strategy, innovative circular economy approaches are required to decouple crop production from environmental degradation. This study evaluates a novel Cascade Hydroponic System (CHS), designed to maximize resource utility by recovering and reusing the drainage from a primary salt-sensitive crop (cucumber) to a secondary, more salt-tolerant cultivation (melon). A comparative Life Cycle Assessment (LCA) is performed in accordance with the Product Environmental Footprint Category Rules (PEFCRs), utilizing primary operational data and direct monitoring of nutrient concentrations in the system’s effluent. The convergence of these elements establishes the novelty of this study. The CHS is benchmarked against a conventional Separated Hydroponic System (SHS) for a functional unit (FU) defined as “the simultaneous production of 1.0 kg of cucumber and 1.0 kg of melon”. The CHS demonstrated lower characterized impacts compared to SHS across all 16 assessed Environmental Footprint categories under the examined pilot-scale conditions. The key findings include reductions of 65.7%, 41.8%, and 30% in Water Use, Climate Change, and Freshwater Eutrophication scores, respectively. Based on the normalization results, the CHS revealed a 58% lower total environmental footprint score compared to SHS. Process contribution analysis indicates that the marked decrease in the environmental burden is associated with the use of fertilizers. While these inputs represent a significant share of the conventional system’s impact scores, their contribution was substantially lower in the CHS. Although based on pilot-scale operational data from a single crop cycle, the results highlight the considerable environmental potential of cascading nutrient reuse configurations, thus enhancing resource use efficiency and mitigating the associated environmental impacts while also contributing novel empirical knowledge to a field that has been limitedly studied.