ADM1-based modeling of anaerobic digestion of swine manure fibers pretreated with aqueous ammonia soaking

Anaerobic digestion of manure fibers present challenges due to their low biodegradability. Aqueous ammonia soaking (AAS) and subsequent ammonia removal has been tested as a simple and cheap method to disrupt the lignocellulose and increase the methane potential and the biogas productivity of manure fibers. In the present study, mesophilic anaerobic digestion of AAS pretreated manure fibers was tested in CSTR-type digesters fed with swine manure and/or a mixture of swine manure and AAS pretreated manure fibers. The Anaerobic Digestion Model No.1 (ADM1) was used for the prediction of the effect that the AAS had on the efficiency of the anaerobic digestion of manure. Kinetic parameters were estimated by fitting of the model to data from manure fed digesters. The model was able to satisfactorily simulate the behaviour of digesters fed with manure. However, the model predictions were poorer for digesters fed with mixture of manure and AAS pretreated fibers, mainly due to the higher hydrolysis rate of the solids of pretreated fibers. Proper modification of the kinetic parameters of ADM1 with emphasis on hydrolysis constants is necessary.