Anaerobic co-digestion of cow dung and cotton seed hull with different blend ratio: experimental and kinetic study
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ORIGINAL ARTICLE
Anaerobic co-digestion of cow dung and cotton seed hull with different blend ratio: experimental and kinetic study R. Venkateshkumar 1
&
S. Shanmugam 1 & AR. Veerappan 1
Received: 18 June 2020 / Revised: 24 August 2020 / Accepted: 10 September 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Anaerobic batch digestion of five different feed reactors was performed under mesophilic temperature at 35 ± 2 °C for a period of 45 days. All the reactors were filled with different combinations of substrates with cow dung and cotton seed hull based on the concentrations of volatile solid with them. The kinetics of biogas production from these feed reactors was studied using different models such as Gompertz model, cone model, Fitzhugh model and logistic kinetic equation. The resulting cumulative biogas production from anaerobic digestion was observed to be 193 ml/g VS and 33 ml/g VS, respectively, with the reactors composed of 100% cow dung (CD) (R1) and 100% cotton seed hull (CSH) (R2). For the reactors composed of mixture of 50% each CD and CSH (R3), mixture of 75% CD and 25% of CSH (R4) and mixture of 25% CD and 75% of CSH (R5), the cumulative biogas productions were 37, 86 and 23 ml/g VS, respectively. Based on the co-efficient of determination (R2) and root mean square error (RMSE), all kinetic models are validated to the best with experimental biogas yield. The cone model showed the good fit for R1, R2 and R4 whereas the logistic kinetic equation showed the good fit for R3 and R5. A new equation is proposed to predict the biogas yield on anaerobic digestion of substrates and its mixture where the digestion period and ratio of mixtures are considered as the input parameters. Keywords Anaerobic co-digestion . Kinetic studies . Gompertz model . Cone model . Fitzhugh model . Logistic kinetic
1 Introduction
S. Shanmugam [email protected]
in the emission of green house gases (GHG). The alternate energy sources need to be renewable, clean, cheap and inexhaustible. Biofuels are the one, produced from the agricultural residues which have high potential to replace the gasoline fuel [1, 2]. Many researchers gave much importance to reduce the consumption of fossil energy and GHG emissions [3]. Biogas yield has been improved by mixing solid waste (agricultural waste) with organic-rich material (animal waste) through anaerobic co-digestion [4, 5]. Biogas is the best alternative renewable fuel to replace fossil fuel as it is non-toxic and easily availed from all decomposed wastes such as animal waste and other biomass [6]. Biogas is produced from the anaerobic digestion (AD) process through various stages such as hydrolysis, acidogenesis, acetogenesis and methanogenesis [7, 8]. Various chemical reactions in the different stages are the following [9]:
AR. Veerappan [email protected]
Hydrolysis : ðC6 H10 O5 Þ n þ nH2 O→n ðC6 H12 O6 Þ
At present, the world is looking for alternate renewable energy sources to meet the current energy demand. Most of the energy are obtained from natural resour
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