BIOGAS PRODUCTION USING ANAEROBIC BIODIGESTER FROM CASSAVA STARCH EFFLUENT WITH RUMINANT BACTERIA AS BIOCATALYST

Abstract

IKMs’ factory activity in Margoyoso produces liquid and solid wastes. The possible alternative was to use the liquid effluent as biogas raw material. This study focuses on the used of urea, ruminant, yeast, microalgae, the treatment of gelled and ungelled feed for biogas production, pH control during biogas production using buffer Na2CO3, and feeding management in the semi-continuous process of biogas production that perform at ambient temperature for 30 days. Ruminant bacteria, yeast, urea, and microalgae was added 10 % (v/v), 0.08% (w/v), 0.04 % (w/v), 50 % (v/v) of mixing solution volume, respectively. The pH of slurry was adjusted with range 6.8-7.2 and was measured daily and corrected when necessary with Na2CO3. The total biogas production was measured daily by the water displacement technique. Biogas production from the ungelling and gelling mixture of cassava starch effluent, yeast, ruminant bacteria, and urea were 22,701 ml and 6,198 ml. Biogas production from ungelling mixture without yeast was 1,830 ml. Biogas production from ungelling mixture added by microalgae without yeast was 1,835 ml and that with yeast was 5,904 ml. Biogas production from ungelling mixture of cassava starch effluent, yeast, ruminant bacteria, and urea in semi-continuous process was 18,161 ml. Adding of microalgae as nitrogen source did not give significant effect to biogas production. Adding of yeast was very helpful to accelerate biogas production. The biogas production increased after adding of cassava starch effluent and yeast. Requirement of Na2CO3 to increase alkalinity of fermenting slurry depends on pH-value. Key Words: biogas cassava; C/N ratio; ruminant bacteria; semi-continuous biodigester; yeast