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 degrees 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, Y-pMAX and theta(MIN)) indicate that the features of the feedstock strongly influence the kinetics of the process. The overall specific growth rate of microorganisms (mu(max)) 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); Y-pMAX = 1.167 L CH4/gDOC(c): theta(MIN) = 7.924 days) vs. 0.135 d(-1) (K= 1.282 d(-1); Y-pMAX = 1.150 L CH4/gDOC(c); theta(MIN) = 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. (C) 2011 Elsevier Ltd. All rights reserved.