Laboratoire des Sciences du sol, de l’Eau et des Géomatériaux, UFR Sciences de la Terre et des Ressources Minières, Université Felix Houphouët-Boigny, Côte d’Ivoire
This study, carried out in San Pedro (Southwest Côte d’Ivoire), evaluates the agronomic valorization of wastewater treatment sludge (WTS) and green waste (GW) through co-composting for sustainable soil improvement and circular economy promotion. Four GW/ WTS formulations (Co1: 0/100, Co2: 25/75, Co3: 50/50, Co4: 75/25) were monitored over 90 days, with regular measurements of temperature, moisture, and pH. Mature composts were characterized for physico-chemical properties, biological maturity, and heavy metal content. A weighted multicriteria matrix, based on ten strategic indicators, identified Co3 as the optimal formulation (score 40/45), outperforming Co4, Co2, and Co1. Co3 reached 65 °C by day 40, satisfying sanitary requirements, maintained optimal moisture, increased soil organic carbon by 284 %, corrected pH to 7.9, and complied with NFU 44-051 heavy metal standards. The heatmap and hierarchical clustering analysis confirmed its superiority, positioning Co3 as a safe and effective amendment for sustainable agriculture adapted to local soils.