Thermal-Kinetics Coupled Analysis of Anaerobic Digestion from Cow Manure in Cold Climates

The kinetics and thermodynamic models of anaerobic digestion were developed and validated with maximum and minimum relative errors of -20.82% and -0.02% in 13 conditions and 199 samples, which could predict biogas production and thermal supplement. The results show methane output increases firstly and then decreases with the increase of HRT and substrate concentration, and HRT should not be below 6 days for an anaerobic digestion of 35 degrees C from cow manure. Both biogas production and thermal load increase with the increase of fermentation temperature. But the growth rate of biogas output is decreasing with the rises of fermentation temperature. In winter of Lanzhou, the larger thermal load brings about the lower reduced heat coefficient, of which the maximum is 2.3 in 25 degrees C. The heat load of anaerobic reactor is inversely proportional to the ambient temperature, while the reduced heat coefficient is proportional to the heat load. In summer and transition seasons, the reduced heat coefficient decreases with the increase of fermentation temperature, which has been greater than 2.0 due to the lower thermal load in Lanzhou city.