Unlocking Synergistic Biogas Potential: Pig Manure and Khat Waste Cosubstrates

Energy scarcity is now a global issue that motivates researchers to explore other energy sources. The purpose of this study was to investigate the possible uses of pig manure (PM) and khat waste (KW) substrate blends for biogas production. The two substrates, namely, PM and KW, initially were treated separately, followed by mixing for anaerobic digestion. In this process, the contribution of mixing ratio (75:25, 50:50, 25:75), temperature (25-45 °C), and hydraulic retention times (30-50 days) on the yield of biogas volume and methane percentage was studied through a central composite design (CCD) experimental design methodology. Consequently, the highest biogas volume of 1831.2 mL and methane percentage of 61.4 wt % were observed at a mixing ratio of 50:50 (PM/KW, %), 45 °C temperature, and hydraulic retention time of 40 days. In summary, the research indicates that utilizing pig manure in combination with khat waste for the production of biogas may be a possible alternative energy source that can address existing global energy challenges.