title: Assessment of models for anaerobic biodegradation of a model bioplastic: Poly(hydroxybutyrate-co-hydroxyvalerate).
abstract: Kinetic models of anaerobic digestion (AD) are widely applied to soluble and particulate substrates, but have not been systematically evaluated for bioplastics. Here, five models are evaluated to determine their suitability for modeling of anaerobic biodegradation of the bioplastic poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV): (1) first-order kinetics with and without a lag phase, (2) two-step first-order, (3) Monod (4) Contois, and (5) Gompertz. Three models that couple biomass growth with substrate hydrolysis (Monod, Contois, and Gompertz) gave the best overall fits for the data (R2>0.98), with reasonable estimates of ultimate CH4production. The particle size limits of these models were then evaluated. Below a particle size of 0.8mm, rates of hydrolysis and acetogenesis exceeded rates of methanogenesis with accumulation of intermediates leading to a temporary inhibition of CH4production. Based on model fit and simplicity, the Gompertz model is recommended for applications in which particle size is greater than 0.8mm.
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, 473 Via Ortega, Stanford, CA 94305, United States. Electronic address: cecily.ryan@montana.edu.
authors.forename: Cecily A
authors.initials: CA
authors.lastname: Ryan
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, 473 Via Ortega, Stanford, CA 94305, United States.
authors.forename: Sarah L
authors.initials: SL
authors.lastname: Billington
authors.affiliation: Department of Civil and Environmental Engineering, Stanford University, 473 Via Ortega, Stanford, CA 94305, United States.
authors.forename: Craig S
authors.initials: CS
authors.lastname: Criddle
mesh_terms: D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D056804:Biofuels; D018533:Biomass; D019149:Bioreactors / Q000382:microbiology; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008697:Methane / Q000096:biosynthesis; D008962:Models, Theoretical; D010316:Particle Size; D010969:Plastics / Q000378:metabolism*; D011091:Polyesters / Q000378:metabolism*; D013997:Time Factors; D000094122:Polyhydroxybutyrates
chemical_list: D056804:Biofuels; D008697:Methane; D010969:Plastics; D011091:Polyesters; C052620:poly(3-hydroxybutyrate)-co-(3-hydroxyvalerate); D000094122:Polyhydroxybutyrates
keywords: Anaerobic digestion; Bioplastic; Kinetics; Modeling; Particle size