National joint research project “BiogasEnzyme”

The use of ligno-cellulose-rich materials like energy crops and agricultural residues becomes increasingly important as feedstock for anaerobic digestion. But using this feedstock may also increases problems in biomethanation process. Ligno-cellulose-rich material is not easily degradable by the abundant bacteria and is supposed to leave the process more or less unaffected. Applying enzymes is considered as one route to improve the digestibility of plant organic material. Several effects of enzyme application were already demonstrated in previous studies: increased conversion of less digestible compounds to biogas, acceleration of biogas formation, and finally decreased viscosity of the treated feedstock. But research into enzyme application still lacks a systematic approach. Therefore, this national joint research project was initiated to proof the direct interaction of feedstock and enzymes in order to understand enhancing effects and to improve the transferability from continuous-flow experiments (lab-scale, pilot plant and full-scale biogas plants) to practice.

In a first step a broad range of commercial single enzymes and enzyme mixtures will be tested (lab-scale, pilot plant) on appropriate feedstocks like maize silage, grass silage, whole crop silage, sudan grass and poultry manure to characterize the mode of actions. This phase will be accompanied by comprehensive monitoring and demonstration activities with selected enzymes at ten full-scale biogas plants. The data received will be the bases for an over-all assessment of enzyme application at farm based biogas plants which comprises cost-benefit-analysis, process assessment and material and energy balances. The findings will result in recommendations for enzyme application in agriculture.