Results from the Extensive Technical Exploitation in a Bio-Gas Facility for the Optimization of Raw Bio-Gas Production for the Gas Power Supply into the Natural Gas Grid

Abstract

The present study indicates that anaerobic mesophilic fermentation of sugar beets, an energy crop, in a mixture with ensiled whole crop maize substrate, for high continuous production of methane (CH4) as a renewable energy source was investigated. Continuous anaerobic digestion of stillage was performed in an stirred tank reactor (CSTR) at 43 ± 1 °C running 286 days. Results showed that maximum specific Gas Production Rate (GPR) of 224 lN/kgFM or 800 lN/kgoTS and CH4 content were 64 % obtained at stillage mixtures with corn silage and sugar beets in the feed. During the entire processing of sugar beets the Extensive Technical Exploitation Plant achieved with a mixture of 30 % corn and 70 % sugar beets a GPR of an average of O 889 lN/kgoTS or 249 lN/kgFM; which lie above the values obtained in laboratory tests. The mesophilic biogas digester was operated in a Organic Loading Rate (OLR) of 6 kgoTs/m³d. The digester worked within the neutral pH range between 7.2 – 7.6 and a degradation rate of 96 %. Due to this substrate and the buffering capacity as well, external supplementation of additives was definitely required to provide a stable and efficient operation, as provided using antifoam in this case. The findings of this ongoing long-term fermentation of an extremely acidic biomass substrate show crucial information about how to appropriately maintain the operational and particularly the environmental parameters in an Extensive Technical Exploitation biogas plant. The produced methane could improve the process energy and economics of a biogas facility.