Modeling the Methane Production Kinetics of Anaerobic Co-Digestion of Agricultural Wastes Using Sigmoidal Functions

Huayong Zhang,Yudong Cao,Di An,Jinxian He,Yonglan Tian

doi:10.3390/en14020258

Huayong Zhang, Yudong Cao + Show 3 more

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https://doi.org/10.3390/en14020258

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Journal: Energies	Publication Date: Jan 6, 2021
Citations: 21	License type: CC BY 4.0

Affiliation: North China Electric Power University

Abstract

The modified sigmoidal bacteria growth functions (the modified Gompertz, logistic, and Richards) were used to evaluate the methane production process kinetics of agricultural wastes. The mesophilic anaerobic co-digestion experiments were conducted with various agricultural wastes as feedstocks, including cow manure, corn straw, grape leaves, vines, wine residue, strawberry leaves, and tomato leaves. The results showed that anaerobic co-digestion of cow manure and other agricultural wastes increased the methane yields while it prolonged the lag phase time. Compared with the modified Gompertz and logistic models, the modified Richards model obtained higher correlation coefficients and was able to fit experimental data better. The results of this study were expected to determine a suitable model to simulate and study the kinetic process of anaerobic co-digestion with mixed agricultural wastes as feedstocks.

Highlights

Anaerobic co-digestion of agricultural wastes turns waste into treasure, which reduces the pollution of waste to the environment, and produces economic benefits [1].Anaerobic co-digestion has attracted many researchers’ attention due to its advantages, such as better nutrient balance, higher biogas yield, and higher residual fertilizer value compared with traditional methods of agricultural waste treatment [2,3,4,5]
Feedstocks used for anaerobic digestion included cow dung (CD), corn straw (CS), grape leaves (GL), vines (VI), wine residue (WR), strawberry leaves (SL), and tomato leaves (TL)
The results showed that A value obtained from the model of the CD + VI group was quite different from the experimental result

Summary

Introduction

Anaerobic co-digestion of agricultural wastes turns waste into treasure, which reduces the pollution of waste to the environment, and produces economic benefits [1].Anaerobic co-digestion has attracted many researchers’ attention due to its advantages, such as better nutrient balance, higher biogas yield, and higher residual fertilizer value compared with traditional methods of agricultural waste treatment (incineration, landfill, composting, etc.) [2,3,4,5]. Most of the previous studies on anaerobic co-digestion of agricultural wastes focused on a direct analysis of experimental data [6,7,8], instead of modeling the methane production kinetics. In order to understand the impacts of agriculture waste types on anaerobic co-digestion, studying the methane production kinetics of anaerobic co-digestion with different feedstocks is necessary [9]. The cumulative methane yields curves in the early stage (slow methane production), the middle stage (fast methane production, i.e., the peak period), and the later stage (slow methane production and stabilization) of anaerobic co-digestion correspond to the lag, exponential, and saturation phases of the growth curve, respectively, showing a sigmoidal curve [11,12]

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Discussion

Conclusion