Pilot-Scale Assessment of Malodor Emissions from Decaying Organic Waste in Awka City, Anambra State, Nigeria

Abstract Malodour generation from decomposing organic wastes contributes a significant environmental and public health challenge in urban settings. This study investigated hydrogen sulfide (H₂S) emissions, sensory odour perception, and physicochemical changes in six common waste types, including fish, broken eggs, meat, tomato, onion, and cabbage, under unsealed and sealed container conditions over 15 days in Awka, Nigeria. Protein-rich wastes consistently produced the highest H₂S concentrations, with peaks of 2,499 ppm for eggs and 1,772 ppm for fish in unsealed bins, whereas plant-based wastes emitted negligible sulphurous gases under open conditions. Sealed containers delayed peak emissions but occasionally elevated cumulative H₂S levels, particularly in plant-based wastes. Sensory evaluation revealed strong alignment between H₂S levels and human-perceived odour intensity and offensiveness, with protein-rich wastes rated highest (r = 0.91, p < 0.001). Physicochemical analyses showed progressive alkalinisation and increased total dissolved solids (TDS) in protein-rich wastes, correlating with H₂S production, while plant-based wastes initially acidified before gradual recovery. Temporal patterns highlighted rapid odour peaks in protein-rich wastes and delayed, gradual emissions in plant-based wastes, illustrating the influence of substrate composition and container condition. These findings emphasise the critical role of waste type, environmental exposure, and physicochemical processes in malodour dynamics and provide practical guidance for municipal waste management strategies, including source segregation, rapid removal of high-protein waste, and container management. Integrating chemical and sensory monitoring offers a predictive framework for mitigating odour nuisance in urban settings.