| Abstract: | A first order kinetic model, developed to predict the behaviour of both batch and semi-continuous anaerobic digestion systems, was tested under laboratory conditions. Two and a half litre glass reactors, using cattle-dung as a feedstock, were run in both batch and semi-continuous modes in temperature-controlled water baths at 35°C. The kinetic model defined constants which could be used to evaluate both systems. The daily gas production data from the batch systems suggested that two rate constants were required to explain them: a higher rate at shorter retention times and a lower rate for longer times. The values of the kinetic rate constant defined for the semi-continuous reactors were considerably higher than those defined for the batch reactors, while the gas production constant was lower. The model offers an effective way to predict the gas production from full-scale digesters running at 35°C, although constants derived from one mode of running should not be used for the other. |
