The main aim of this work is to study the biogas production from different agricultural residues to overcome the energy scarcity and environmental pollution. To achieve that study the different types of mixing (Dairy manure (100:0), Poultry litter (100:0), Dairy manure, poultry litter and rice straw (25:25:50), Dairy manure and rice straw (20:80), Dairy manure and rice straw (80:20), Dairy manure, poultry litter and rice straw (40:40:20) and Poultry litter and rice straw (50:50)) on the total solids, volatile solids of slurry, biogas yield, methane yield, CO₂ and H₂S. The results show that the total solids (TS) and volatile solids (VS) of slurry decrease with increasing retention time for all treatments. The highest value of accumulated biogas yield (260.93 m³ per ton TS) was found with the Poultry litter and rice straw (50:50). Meanwhile, the lowest value of accumulated biogas yield (229.96m³ per ton TS) was found with Dairy manure, poultry litter and rice straw (25:25:50). The highest value of accumulated methane yield (196.10 m³ per ton TS) was found with the Poultry litter and rice straw (50:50). Meanwhile, the lowest value of accumulated methane yield (156.30 m³ per ton TS) was found with Dairy manure (100:0). CO₂and H₂S increase with increasing retention time for all treatments.