Co- Digestion of Neem (Azadirachta indica) Shoot Biomass with Poultry Droppings: Effect of Pretreatment Methods on Biogas Production

Abstract

Inadequate energy supply, environmental pollution, and declining soil fertility are major challenges in developing nations like Nigeria. Despite the abundance of biomass, much of it ends up as unmanaged solid waste. This study evaluated the effects of pretreatment on biogas yield from the co-digestion of Neem (Azadirachta indica) shoot biomass with poultry waste and cow rumen (inoculum). Materials were sourced from LAUTECH and prepared by washing, blending (mechanical pretreatment). The blended neem shoot was pretreated in a water bath to about 60 degrees Celsius for 1hr 20 minutes (thermal pretreatment). Chemical pretreatment was adopted to aid in the degradation of the lignin content. 4g of NaOH was dissolved in distilled water and then added to the thermally blended biomass. Two batches were prepared from the chemically treated Neem shoots, with poultry waste (batch A) and cow rumen (batch B), and put into airtight biodigesters. Physicochemical parameters (pH, TN, TP, TC, BOD, COD, MC, TS, C/N, FS) of both slurry and digestate were analyzed using standard methods. Biogas production, pH, and temperature were monitored over 30 days, and gas composition was determined via Gas Chromatography-Mass Spectrometry. Batch A showed biogas yields of 0.1016–0.0326 L/day, pH 8.39–8.41, and 35.7–35.8°C; Batch B yielded 0.1628–0.0488 L/day, pH 8.36–8.39, and 35.7–35.8°C. Methane content was 61.29% in Batch A and 63.29% in Batch B. ANOVA indicated significant differences in yields (p = 0.0256 for A, p = 0.0200 for B). Results showed that co-digestion, particularly with cow rumen, improved methane output. The produced methane is suitable for use in cooking, heating, and electricity generation, offering a sustainable solution for waste-to-energy conversion in Nigeria.