Kinetics of batch anaerobic co-digestion of poultry litter and wheat straw including a novel strategy of estimation of endogenous decay and yield coefficients using numerical integration

Abstract

The kinetics of anaerobic co-digestion of poultry litter and wheat straw has not been widely reported in the literature. Since endogenous decay and yield coefficients are two basic parameters for the design of anaerobic digesters, they are currently estimated only by continues experiments. In this study, numerical integration was employed to develop a novel strategy to estimate endogenous decay and yield coefficients using initial and final liquid data combined with methane volumes produced over time in batch experiments. To verify this method, the kinetics of batch anaerobic co-digestion of poultry litter and wheat straw at different TS and VS levels was investigated, with the corresponding endogenous decay and (non-observed) yield coefficients in the exponential periods determined to be between 0.74 × 10-3 and 6.1 × 10-3 d-1, and between 0.0259 and 0.108 g VSS (g VS)-1, respectively. A general Gompertz model developed early for bio-product could be used to simulate the methane volume profile in the co-digestion. The same model parameters obtained from the methane model combined with the corresponding yield coefficients could also be used to describe the VSS generation and VS destruction.