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

Bioprocess Biosyst Eng (2016) 39:15531565 DOI 10.1007/s00449-016-1630-9

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

Jiacheng Shen1 Jun Zhu1

Received: 12 February 2016 / Accepted: 20 May 2016 / Published online: 27 May 2016 Springer-Verlag Berlin Heidelberg 2016

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 coefcients 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 coefcients using initial and nal 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 coefcients in the exponential periods determined to be between 0.74 9 10-3 and6.1 9 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 prole in the co-digestion. The same model parameters obtained from the methane model combined with the corresponding yield coefcients could also be used to describe the VSS generation and VS destruction.

Keywords Anaerobic digestion Endogenous decay

Gompertz model Poultry litter Wheat straw Yield

coefcient

List of symbolsb Fitted constant in the Gompertz model (dimensionless)c Fitted constant in the Gompertz model (d)e Base of the natural logarithm

(dimensionless)gmp Maximum bio-product rate (i.e., at the deection point of P vs. t curve)

(mL d-1)

K Maximum rate constant in theMonod model (d-1)

KS Half-saturation rate coefcient in the

Monod model (g)kd Endogenous decay coefcient (d-1)

m Sample sizeP Cumulated biogas volume (mL)

Pi Value of point i calculated from the modelsPm Maximum gas volume (mL)

P0 Fitted constant in the Gompertz model (mL)

pi Observed value of point ip Mean of the observed dataR2 Coefcients of determinationS Substrate mass in the digester represented by the volatile solid (VS)(g)