Study of Biogas Production from Cassava Industrial Waste by Anaerobic Process

¹ Department of Chemical Engineering, Engineering Faculty, Diponegoro University, 50275 Semarang, Indonesia
² Master Program of Environmental Science, School of Post Graduate Studies, Diponegoro University, 50275 Semarang, Indonesia

^* Corresponding author: budiyono@live.undip.ac.id

Abstract

Biogas production processes from tapioca wastewater have several problems that cause the biogas production is not optimal, such as pH drop at beginning of the process because the rate of acid formation is too fast and the rate of starch wastewater degradation is too slow. Therefore, to obtain optimal biogas production it is required two-stage reactor. The purposes of this research were to (i) study the influence of one stage fermentation and two stage fermentation on biogas production, (ii) study the effect of buffer Na2CO3 on biogas production, and (iii) study the effect of methanogenic bacteria concentration on biogas production from cassava starch effluent. The first method of our research was hydrolysis process by “Saccharomyces cereviceae” as substrate activator. The second is the arrangement of pH and the last is process of methane production. The results showed that the highest biogas production is achieved at concentration of methanogenic bacteria 20% (v/v) that is equal to 2458 ml. At concentration of 8% (v/v) and 15% (v/v), biogas production was 2105 ml and 2117 ml. The addition of Na₂CO₃ can extend to 16 days with accumulation of 372 ml. While without the addition of buffer, biogas production period was only 9 days with accumulation of 620 ml. In semi continuous process, the analysis carried out every 3 days. Highest biogas production achieved in the variable addition of yeast with the accumulation 9329 ml. Without yeast, accumulation of biogas was 6831 ml. Yeast is use as substrate activator so it can accelerate the hydrolysis process and increased biogas production. The addition of Na₂CO₃ is increase the alkalinity so the pH drop did not occur early in the process.