Co-fermentation of carrots, grain residues and potato chips

Abstract

Abstract. Different raw organic materials can be used for production of methane in the anaerobic fermentation process. Every kind of biomass has the specific methane production potential. In practice, different biomasses are utilised in the biogas plant at the same time often, so enabling co-fermentation at different proportions. The purpose of this study was to ascertain how the co-fermentation of various biomasses affects the methane yield compared to methane release from the same biomass during its mono-fermentation. Different factors may influence the methane yield, and most important are carbon: nitrogen (C: N) ratio, presence of easy degradable carbohydrates, trace elements and other substances needed to provide optimal microbial activity. Investigations were provided in 16 bioreactors with volume 0.75 l operating in batch mode at the temperature 38°C. Equal amounts of the carrots, grain drying residue, potato chips and inoculums were processed in 3 different groups of bioreactors to observe methane production from individual biomass, mixed with inoculums, in the monofermentation process. The same biomasses, in proportion 1:1:1 by weight, and inoculums were mixed together and co-fermented in the fourth group of bioreactors. 2 bioreactors were filled with inoculums only for control. It was found that average specific methane production per gram of dry organic matter in the co-fermentation process was higher compared to average specific methane production obtained from the same biomasses (carrots and grain residues) in the mono-fermentation process, when each biomass was fermented individually.