<p>This study presents an innovative approach to enhancing the efficiency of composting organic municipal solid waste (MSW) and improving fertilizer quality using a pilot Aerated Static Pile (ASP) system with extremophilic lake sediment as a microbial inoculum. By optimizing waste mixing ratios, refining operational parameters, and assessing the quality of the resulting organic fertilizer, the research provides significant insights into sustainable waste management solutions suitable for rapidly urbanizing areas like Ethiopia. Various mixtures of biodegradable MSW, cow-dung, and extremophilic lake sediment as inocula were tested, with key composting parameters, including pH, C/N ratio, moisture content (MC), and electrical conductivity (EC), monitored to identify ideal composting conditions. Additionally, heavy metal concentrations were analyzed pre- and post-composting to ensure product safety. Optimal conditions were achieved with pH values of 5.43 to 7.89, a C/N ratio between 23:1 and 42:1, MC ranging from 60 to 66%, and EC 4.10% and 5.24%. Heavy metal levels consistently met regulatory safety standards. Among the inocula tested, extremophilic lake sediment (Run I) showed superior decomposition performance compared to cow dung (Run II), with Pile P3 (50% food waste, 50% yard waste) producing the highest-quality compost, followed by Pile P2 (75% food waste, 25% yard waste). In contrast, Pile P4 (25% food waste, 75% yard waste) displayed lower temperatures, resulting in slower decomposition rates. This research underscores the practical value of ASP composting and extremophilic lake sediment as a microbial inoculum for producing high-quality compost, contributing to effective organic waste management strategies in Ethiopia and comparable regions globally.</p> Graphical Abstract <p></p>