Study on co-fermentation of cow dung (CD) and giant dirt (GD - Pistia stratiotes L.) in semi-continuous anaerobic digesters aims to test biogas quantity and quality by time. Three mixing rates counted based on ODM of each material were chosen: 100 %CD, 50 %CD+ 50 %GD, and 100 %GD. The experiments were set up in laboratory conditions with two types of digesters: one-stage digesters and two-stage digesters (triplicate for each treatment). After 80 days, the biogas produced from the one-stage digesters was not significantly different to the two-stage digesters with similar input material. The highest production of biogas came from digesters of 100 %GD - 235.8 L for the one-stage and 240.3 L for the two-stages. The medium production came from digesters of 50 %CD+50 %GD - 127.8 L for the one-stage and 118.4 L for the two-stages. After one month, the percentage of CH₄ was high enough for burning and almost giant dirt was digested that avoids a blockage inside the digesters. The results showed that co-fermentation of GD and CD is an alternative for livestock raising households to produce biogas for energy purpose.