Molecular Analyses of Microbial Communities Reveal an Optimization of the Anaerobic Fermentation Process for Improved Biogas Production during Calcium-Nitrate Treatment

摘要

The production of renewable energy in industrial scale is among the primary research topics worldwide. In this context, the anaerobic digestion of volatile organic solids such as maize silage, manure and organic waste is used for the industrial production of biogas as a resource of renewable energy. One of the primary goals of biogas production plants is the optimization of the fermentation process towards a high-quality biogas. The most valuable component of high-quality biogas is the clean-burningmethane (CH4), whereas hydrogen sulfide (H2S), a side product of the anaerobic fermentation process, is unfavorable. Therefore, a major aim in the optimization of the anaerobic fermentation process is to maximize CH4 production while minimizing H2S production. Empirical observations and reports of industrial plant operators repeatedly confirmed an improvement of biogas quality after dosage of a calcium-nitrate CafNOah solution to the anaerobic fermentation process. Therefore, we sampled control fermenters and fermenters treated with Ca(N03h and analyzed the structures and functions of microbial communities using molecular methods. We found a shift in community structure after treatment with Ca(N03>2 to the benefit of denitrifiers and methanogens and atcost of sulfate reducing bacteria (SRB). Furthermore, quantitative real time PCR experiments revealed a significantly increased denitrification and methanogenesis activity, while sulfate reduction was notably reduced in most cases. We here propose a mechanistic concept for the mode of action of Ca(N03>2 as a tool to optimize the anaerobic fermentation process for the production of improved biogas quality.