Six digesters made from transparent plastic with a capacity of 10 l (digestion volume of 7.5 l) were used for producing biogas. Four different organic wastes were used (fresh cattle dung, cotton stalks, water hyacinth and sugar beet). The digesters were experimented under six different fermentation mixtures (A, B, C, D, E and F) and three different particle sizes (5, 10 and 15 mm) .Digesters performance was evaluated through measuring daily gas production, cumulative biogas production, methane production and chemical analysis for biogas slurry such as nitrogen percentage and pH value. The experimental results revealed that the maximum daily biogas production and cumulative biogas values were 8.03 l and 108.3 l respectively and also the maximum methane production value was 6.16 l for mixture D and particle size of 5 mm. as the highest nitrogen percentage and pH values were 4.3% and 6.83 for the mixture C and B respectively and particle size of 5 mm.