Experimental Procedure, Start by chopping the water lettuce thoroughly and mixed with pig manure in different ratios. Then put into the tank. The tank are the same size and sealed so air can not get inside but there is the pipe will bring gas from the tank to measure the volume of generate gas inside the tank and store The gas samples. The experimental will take 60 days and control temperature at 35 + -2 and The gas samples were taken for composition, including the amount of methane, Carbon dioxide, oxygen, Nitrogen. The gas samples were collected every 5 days.