The organic waste fractions ratio optimization in the anaerobic co-digestion process for the increase of biogas yield

Abstract

Biogas obtained by anaerobic digestion process from various organic fractions of waste is increasingly used as a renewable energy sources for the generation of electricity and heat. The quantity of biogas produced by anaerobic digestion depends on many factors: types and characteristics of organic waste, elemental composition of waste, C/N ratio, pH value, inhibitors, retention time, content of nutrients, etc. In addition to the selection of parameters that influence the process of anaerobic digestion, biogas yield can also be influenced by choosing the optimal combination and ratio of organic fractions of waste. In this paper, an analysis of the influential parameters in the process of anaerobic digestion was performed on biogas yields and an overview of the essential characteristics of waste (elementary composition, C/N ratio, lignin content, etc.) for different fractions of organic waste (organic municipal waste, various types of waste of animal origin, as well as agricultural waste). In order to choose the optimal mixing ratio of different fractions of organic waste for maximum biogas yield, a mathematical model has been developed using the multi-criteria optimization method. The boundary conditions set for the multi-criteria optimization was the C/N ratio in the range of 20 to 30 and the minimum content of the lignin in the substrate. The application of the developed model was carried out on the case study of the city of Nis, and the optimal mix of different types of organic waste was determined, as well as the optimal amount of each waste fraction and biogas yield.

Co‐Digestion of Water Hyacinth and Duck Manure for Potential Low‐Cost Biogas Production by Rural Communities

“…Duck manure was also reported to help maintain optimal pH for biogas production when used as a co‐substrate with other wastes. [ 42 ] As methanogens are more resistant to pH changes, [ 43 ] the mixture of WH and DM can be seen to produce favorable pH conditions for these bacteria to proliferate and enhance biogas production. Nevertheless, the impact of duck manure ratios in maintaining pH was not significantly proven in this study, as mentioned above.…”

“…[ 37 ] This is supported by the results obtained in this study as pH increased toward alkaline conditions rather than decreased with the accumulation of VFA. [ 43 ] Additionally, WH has also been reported to be a good buffer in maintaining the pH in co‐digestion with other wastes. [ 44 ]…”