Improved Biogas Production from Chicken Manure Anaerobic Digestion Using Cereal Residues as Co-substrates

Abstract

Because of the resource abundance and high total nitrogen content, chicken manure (CM) is very suitable for anaerobic digestion (AD). In this study, a set of comparative assays was performed on the AD of CM using three main cereal residues (CRs) as co-substrates under various mixing combinations, with a total solid concentration of 8%. Under mesophilic conditions at 35 ± 1 °C, all combinations of CM and CRs significantly improved biogas and methane yields. Co-digestion of CM and corn stalks (CS) showed higher cumulative biogas productions than that of CM/wheat straw (WS) and CM/rice straw (RS). After 60 days of fermentation, the highest methane contents were produced by CM/WS, CM/CS, and CM/RS at a total solid (TS) ratio of 50:50 of 345, 383, and 378 mL/g of removed volatile solids (VSremoved), respectively. The value between 15 and 25 has been suggested as the optimal range of the C/N ratio for the co-fermentation of CM with CRs. The results of the volatile fatty acid/alkalinity analysis clearly demonstrated that the co-digestion of CM and CRs was conducive for not only improving biogas production but also stabilizing the digestion system. Predicted optimum CM/CRs proportions, optimum C/N ratios, and maximum biogas productions were calculated according to the best fit regression models for co-digestion of CM with CRs.