Optimization of anaerobic co-digestion of Solidago canadensis L. biomass and cattle slurry

SC (Solidago canadensis L.) was digested with CS (cattle slurry). The process stability, methane production by anaerobic digestion, and the efficiency of organic matter removal were measured. The maximum methane production of 143.7 L/kg volatile solids was obtained at a SC:CS ratio of 1:3 and a substrate concentration of 6% (based on volatile solids); however, the difference between total methane production for SC:CS ratios of 1:1 and 1:3 was not significant (p > 0.05). Therefore, based on the SC treatment capacity, the optimum SC:CS ratio is 1:1 for this application. For a 6% substrate concentration, the total methane production (129.6 L/kg volatile solids) at a SC:CS ratio of 1:1 was 123.5% higher than that of a control. The pH was fairly constant (6.8-7.6). The removal efficiencies of total solids, volatile solids, cellulose, hemicellulose, and soluble chemical oxygen demand were 37.3, 41.6, 23.6, 34.8, and 38.8%, respectively, and the T80 was 30.0% shorter than that for maximum methane production. These results indicate that the process stability and methane production efficiency of SC can be improved by CS addition.