Market waste composition, biomethane yield, and energy potential in Nairobi, Kenya

Abstract

Introduction: Municipal solid waste (MSW) management remains a critical sustainability challenge in rapidly urbanizing cities, particularly in Sub-Saharan Africa where inadequate infrastructure and reliance on unsanitary landfills exacerbate greenhouse gas emissions. Nairobi, Kenya, generates approximately 3600 tons of MSW daily, with up to 40% uncollected, straining the only dumpsite at Dandora. Material and methods: This study investigated the biomethane potential of waste from 23 food markets, applying standardized compositional analysis and anaerobic digestion (AD) protocols. Results: Results show that market waste is predominantly organic (67%), with significant variability in moisture content, volatile solids (VS) and total solids (TS). The City market exhibited the highest biomethane potentials (76.27 m 3 /ton), while En recorded the lowest values (36.51 m 3 /ton). Inferential statistics confirmed significant heterogeneity across markets (Kruskal–Wallis, p < 0.001), with regression analysis explaining 97.4% of yield variance. The final regression model identified moisture content as the strongest negative predictor (β = 0.883, p < 0.001). Collectively, the 289 tons of organic market waste produced daily could generate ~14,230 m 3 of biomethane, equivalent to 137,000 kWh of energy. Conclusions: These findings highlight AD as a viable waste-to-energy pathway, offering renewable energy generation, climate mitigation, and employment opportunities. Policy recommendations include enhanced waste segregation, centralized biogas facilities, and integration of predictive modelling into urban energy planning.