The cow manure can be used for making fertilizer or biogas. The objective of this research is to find the best combination of factors and levels, for improving the quality of biogas, which can be used in the pasteurization process of milk production. A study case is done at a milk industry in the Middle Java province. Design of experiment with Taguchi method was used to find the best combination, for producing biogas with high methane percentage. The conclusion is made based on the analysis of mean and variance (signal to noise ratio) of the experiment’s response. As a result, the best combinations are the ratio of grass and maize plant is 1 : 0, without cutting process and they are given twice in a day1) the composition of biogas’s making is 1 liter of water for 3 kilograms cow manure2) the amount of bio starter is 6 milliliters for every 30 kilograms biogas dough3) and the food composition for a cow is 0,04 kilograms mineral, 0,03 kilograms sugar palm, 12 kilograms bran, and 18 kilograms tofu dregs4)
