Kinetic study of thermophilic anaerobic digestion of cattle manure in a continuously stirred Tank Reactor under varying Organic Loading Rate

This study established a kinetic model for predicting biogas production using a Continuously Stirred Tank Reactor (CSTR) digesting cattle manure under varying Organic Loading Rate (OLR) at Thermophilic Temperature (TT) of 56 ±1°C . The daily reactor loading was commenced at an OLR of 1.0 g_.oTS/L.d. This (OLR) was increased fortnightly by 0.5 g.oTS /L.dtill an OLR of 5.0 g.oTS /L.dwas attained. At this point, the biogas and methane yields were no longer commensurate with the feeding and the reactor was adjudged failing. The volume of biogas produced was measured and analysed for CH₄, CO₂, H₂S and CO using an Infrared gas detector (PRONOVA). The experiment was run continuously for about 140 days. The biogas yields corresponding to OLR of 1.0, 1.5, 2.0, 2.5, 3.0, 3.5, 4.0, 4.5 and 5.0 g.oTS /L.d were 0.420, 0.370, 0.420, 0.450, 0.430, 0.430, 0.400, 0.380 and 0.360 L/goS respectively. The highest biogas yields of 0.45 L/goS was recorded at an OLR of 2.5 goTS/l.d. The average methane content was 57%. The kinetic model developed related biogas yield with OLR and could be used to dimension CSTR experiment digesting animal manure.