Sustainable Nutrient Recovery from Porcine Slurry: Agronomic Evaluation of Filtered and Ozonated Effluents in Internet-of-Things-Enabled Aeroponic Lettuce Cultivation

Intensive porcine livestock production generates approximately 15 million cubic meters of slurry annually, exerting significant environmental pressure on groundwater and contributing to greenhouse gas emissions. The AEROFER project aims to mitigate this impact by demonstrating the conversion of nitrogen-rich waste into liquid fertilizers for soilless cultivation. Using an Internet of Things (IoT)-enabled aeroponic platform controlled by an ESP32 microcontroller, this study evaluated filtration (40 microns) and ozone-based stabilization (N-Amatic technology). Three lettuce varieties (Lactuca sativa L.)—Longifolia (Romaine lettuce), Capitata (Butterhead lettuce), and Capitata (Red leaf lettuce)—were grown to compare Filtered Slurry (FS) and Filtered–Ozonated Slurry (FOS) against a mineral control standard solution (SS). The results indicate that ozone treatment eliminated detectable E. coli and coliforms while increasing the phosphorus availability by 78% (from 30.9 to 55 mg/L), despite an 11% reduction in the potassium content (from 180 to 160 mg/L). Agronomic data reveal variety-specific responses, and mass balance analysis shows that the solutions are potassium-deficient, meeting only 32–64% of crop needs. In conclusion, while aeroponics is a viable tool for nutrient recovery and requires targeted mineral supplementation to achieve full parity with commercial fertilizers, it satisfies a substantial proportion of plant nutritional requirements. Consequently, it represents a sustainable approach to food production through waste recycling, contributing to a circular economy in the pig industry without apparent sanitary risks.