The aim of this study was to obtain the best combination of factors that could be easily manipulated by men to optimize the production of biogas. To evaluate the anaerobic digestion of goat manure, we used 24 digesters distributed in factorial design 3 × 3 × 3 × 2, and considered the following factors: temperature (20.1°C, 21.5°C, 30.2°C, 33.7°C and 34.7°C), pH (6.8, 6.84, 7.01, 7.15, 7.22), total solids (2.6%, 3.5%, 4.5%, 6.8%, 6.9%), and type of shape (whole goat manure and broken goat manure) in a central composite design. Data were analyzed as a mixed model with fixed effect of temperature, pH, TS, shape of manure, and their interactions and the random effect of day and digester, using the PROC MIXED procedure of SAS (version 9.0). The shape of manure did not affect biogas production. The isolated effect of temperature and pH in the biogas production was not significant whereas only the highest level of total solids resulted in greater biogas production by day (0.11 m³ ± 0.02; P = 0.0008). We also observed interaction among temperature, pH, and total solids (5.36 m³ ± 0.12 P = 0.0020) on the biogas production. Additionally, the percentage of methane in the biogas was not affected by the amount of total solids, pH, and temperature in the biodigester. The best volume of biogas production was obtained when the following values were applied: 34.7 (temperature), 6.8 (pH) and 7.0 (total solids). Our results reveal that even under low pH and low temperature, biogas production increases as a function of increasing total solids of goat manure, however none of the factors affected the proportion of methane in the biogas. The fact that we detected the best biogas yield using 6.8% total solids is extremely important, because a greater supply of substrate requires fewer amounts of water and time, it is less labor-intensive, while methane production is greater than that found using 5% total solids. Even though water returns in the biofertilizer form, if less water is required through biodigestion it would represent a significant water saving.