The Comparison of Mesophilic and  Thermophilic Anaerobic Digestion

Abstract

AbstrAct Purpose: of this paper is to compare mesophilic and thermophilic anaerobic digestion of three maize varieties. Parameters such as biogas production and biogas composition from maize silage were measured and calculated. The amount of biogas production (methane) was observed by the mini digester. Design/methodology/approach: Biogas production and composition in mesophilic (35 degrees C) and thermophilic (55 degrees C) conditions were measured and compared. The measurements were performed with mini digester according to DIN 38414 part 8. We used three different maize varieties (NK PAKO, PR34N43 and RAXXIA). Findings: Biogas yields ranged between 315 -409 Nl kg VS -1 in mesophilic conditions and 494 – 611 Nl kg VS -1 in thermophilic conditions. The highest biogas yield was in case of NK PAKO (611 NI kg VS -1) in thermophilic conditions. The lowest biogas yield was in case of PR34N43 (315 NI kg VS -1) in mesophilic conditions. Biogas quality produced in thermophilic temperature range is better than biogas quality produced in mesophilic temperature range. Thermophilic digestion is 4 times more intense, has higher VSS removal efficiency and yields more biogas. Research limitations/implications: Thermophilic stabilization of energy plants at 55°C is truly economical, more biogas is produced. The only disadvantage of thermophilic stabilization is that more energy is used for heating fermenters. Therefore, further researches are necessary. Practical implications: For biogas plants with mesophilic digesters we suggest an upgrade of existing mesophilic digesters (35°C) to thermophilic digesters (55°C), which is an economically beneficial solution compared to construction of additional mesophilic digesters. Originality/value: The mini digester for biogas production was built as special equipment. It can be used in mesophilic and thermophilic conditions. The quality of the produced biogas is determined with a gas analyser GA 45. Reference to this paper should be given in the following way: P. Vindis, B. Mursec, M. Janzekovic, F. Cus, The impact of mesophilic and thermophilic anaerobic digestion on biogas production, Journal of Achievements in Materials and Manufacturing Engineering 36/2 (2009) 192-198.