Improving the Efficiency of Large-Scale Biogas Processes: Pectinolytic Enzymes Accelerate the Lignocellulose Degradation

Abstract

An enzyme preparation containing mainly pectinolytic activity was used to increase the hydrolysis of agricultural feedstock for production of biogas at lab and industrial-scale bioreactors under mesophilic conditions. Bioreactor performance was evaluated by determining lignocellulose degradation efficiency and specific methane yields over a residence time of 65 days for various substrates. Additionally, enzymatic activity assays were carried out in laboratory trials to investigate the hydrolytic potential of the enzyme preparation. During industrial-scale trials the viscosity (shear stress from torsion) was measured in fermentation media. At an applied concentration of 200 g enzyme preparation/t DM of maize silage in lab-scale biogas processes, the degradation of hemicellulose was enhanced and the specific methane production was increased by 42 l_N/kg ODM (15%) in comparison to untreated maize silage. Using enzymatically treated rye silage, the hemicellulose was utilized to a higher degree and the specific methane production enhanced by 26 l_N/kg ODM (10%). Results from the industrial trial showed that enzymatic pretreatment (100 g enzyme/t DM of substrate) of different substrate mixtures containing mainly maize silage increased the lignocellulose degradation, in particular hemicellulose and a substantial increase in specific energy production was obtained. In addition, the viscosity in the fermentation media was significantly reduced up to 18%. In conclusion, the addition of an enzyme preparation as biological treatment led to an economical operating improvement in efficiency of the biogas process.