The economic analysis in this research is done for small scale ranch, with target to generate electricity power of 2
kW that run for 24 hours per day, therefore the electricity energy to be generated is 48 kWh per day. The data obtained from literatures are cow manure total solid content approximately of 20.5% weight in wet bases [14],
include degraded compounds i.e. protein 12.5% weight dry base, cellulose 31% weight dry base, starch 12.5%
weight dry base, and hemicellulose 12% weight dry base [15], and the minimum retention time in biogas production
approximately of 10-15 days [16]. By using Equation 1-6, there are obtained the rate of cow manure to be fed to
digester as much as 534919.4 gram per day (534.9194 kg per day) and the digester volume of 16.7162 m3 when the
safety factor is 0.25 or 25%. Due to the conversion factor used in the previous research about 60% [1], it is obtained
the solid fertilizer from the digester sludge approximately of 64917.82 gram per day or 64.9178 kg per day.