In this research a fixed- dome Biogas unit (Chinese’s model) with a capacity of 1.8 m3 gas/day and 50 days retention time was designed and installed. The diameter of the hemispherical digester was 3 meters witch was built with masonry material (brick, cement, sand). In this unit, digested slurry will go out trough a channel with dimensions of 1.35 * 0.65 * 1.25 m. by oneness of an easy technology a kind of mechanical agitator (Paddle mixer) was designed and installed on the plant The unit was loaded daily with 40 kg cow manure and vegetable residue during 4 weeks. The amount of biogas production after mixing the slurry was measured via dry gas-meter in the end of each week. After mixing the slurry by designed agitator the average of biogas production increased about 42%.A water trap was used for eliminating the water vapor; furthermore the amount of BOD5 and COD in the anaerobic digester reduced to 90.2% and 89.2% respectively, and the average of pH for digested slurry was measured about 7.5. It should be mentioned that pressure of generated biogas was read about 25 cm H2O during four weeks.
)