Dry-thermophilic anaerobic digestion of organic fraction of municipal solid waste: Methane production modeling

The influence of particle size and organic matter content of organic fraction of municipal solid waste (OFMSW) in the overall kinetics of dry (30% total solids) thermophilic (55 °C) anaerobic digestion have been studied in a semi-continuous stirred tank reactor (SSTR). Two types of wastes were used: synthetic OFMSW (average particle size of 1 mm; 0.71 g Volatile Solids/g waste), and OFMSW coming from a composting full scale plant (average particle size of 30 mm; 0.16 g Volatile Solids/g waste).A modification of a widely-validated product-generation kinetic model has been proposed. Results obtained from the modified-model parameterization at steady-state (that include new kinetic parameters as K, YpMAX and θMIN) indicate that the features of the feedstock strongly influence the kinetics of the process. The overall specific growth rate of microorganisms (μmax) with synthetic OFMSW is 43% higher compared to OFMSW coming from a composting full scale plant: 0.238 d−1 (K = 1.391 d−1; YpMAX = 1.167 L CH4/gDOCc; θMIN = 7.924 days) vs. 0.135 d−1 (K = 1.282 d−1; YpMAX = 1.150 L CH4/gDOCc; θMIN = 9.997 days) respectively.Finally, it could be emphasized that the validation of proposed modified-model has been performed successfully by means of the simulation of non-steady state data for the different SRTs tested with each waste.

► Methane generation may be modeled by means of modified product generation model of Romero García (1991).
► Organic matter content and particle size influence the kinetic parameters.
► Higher organic matter content and lower particle size enhance the biomethanization.