Anaerobic fermentation of cattle manure: Modeling of hydrolysis and acidogenesis

A mathematical model for the hydrolysis and acidogenesis reactions in anaerobic digestion of cattle manure is presented. This model is based on the premise that particulate hydrolysable fraction of cattle manure is composed of cellulose and hemicellulose that are hydrolyzed at different rates according to a surface-limiting reaction; and, that the respective soluble products of hydrolysis are utilized by acidogens at different rates, according to a two-substrate, single-biomass model. Batch experimental results were used to identify the sensitive parameters and to calibrate and validate the model. Results predicted by the model agreed well with the experimentally measured data not used in the calibration process, with correlation coefficient exceeding 0.91. These results indicate that the most significant parameter in the hydrolysis–acidogenesis phase is the hydrolysis rate constant for the cellulose fraction.