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

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.