Production of volatile fatty acid in biogas digester with coal media

The need for environmentally friendly energy can be sought by using a consortium of microorganisms originating from dairy cow feces in a biogas digester with sub-bituminous coal media. This study aims to determine the effect of adding consortium from dairy cow feces on coal media in biogas digester on pH of digester and volatile fatty acid production. This study used an experimental method using a randomized block design consisting of four treatments based on the consortium microorganism inoculum given (P1 = powder inoculum (mixture of inoculum from coal and dairy cow feces), P2 = inoculum from coal, P3 = inoculum from dairy cow feces, and P4 = without using inoculum) and six groups based on fermentation time (I = 10 th day, II = 20 th day, III = 30 th day, IV = 40 th day, V = 50 th day, and VI = 60 th day). The pH conditions of the digester in all treatments ranged from 6.438 -6.597, and the production of volatile fatty acids ranged from 153.083-162.333 mM. The results of the analysis in this study indicated that the addition of various types of consortium microorganism inoculums in the biogas digester medium produced similar pH conditions and volatile fatty acids. The production of increased concentrations of volatile fatty acids was directly proportional to the decrease in pH conditions.