Biomedicine and Biotechnology
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Biomedicine and Biotechnology. 2014, 2(4), 93-101
DOI: 10.12691/bb-2-4-5
Open AccessArticle

Quadratic Yield Response of Methane Gas to Input Ratio of Organic Loading Rate and Hydraulic Retention Time during Microbial Digestion of Fruit Wastes

C. I. Nwoye1, , I. C. E. Umeghalu2, S. E. Ede3, N. I. Amalu4, W. C. Onyia3 and N. E. Idenyi5

1Department of Metallurgical and Materials Engineering, Nnamdi Azikiwe University, Awka, Nigeria

2Department of Agric and Bioresoures Engineering

3Department of Metallurgical and Materials Engineering, Enugu State University of Science & Technology, Enugu, Nigeria

4Project Development Institute Enugu

5Department of Industrial Physics, Ebonyi State University, Abakiliki, Nigeria

Pub. Date: December 25, 2014

Cite this paper:
C. I. Nwoye, I. C. E. Umeghalu, S. E. Ede, N. I. Amalu, W. C. Onyia and N. E. Idenyi. Quadratic Yield Response of Methane Gas to Input Ratio of Organic Loading Rate and Hydraulic Retention Time during Microbial Digestion of Fruit Wastes. Biomedicine and Biotechnology. 2014; 2(4):93-101. doi: 10.12691/bb-2-4-5


The yield response of methane gas during microbial digestion of fruit wastes was evaluated based on the operational input ratio of organic loading rate (OLR) and hydraulic retention time (HRT). Computational analysis of generated experimental results indicates that the yield response was empirically a two-factorial quadratic model which was validated for predictive analysis and evaluation. The validity of the model; ζ = 2.1863 (ϑ/ɤ)2 - 2.4573 (ϑ/ɤ) + 0.72 was rooted on the core model expression ζ - 0.72 = 2.1863(ϑ/ɤ)2 – 2.4573 (ϑ/ɤ) where both sides of the expression are correspondingly approximately equal. Results of methane gas yield were generated using regression model and its trend of distribution was compared with that from derived model for the purpose of verifying its validity relative to experimental results. The results of the verification process show very close dimensions of covered areas and shapes designating methane gas yield, which precisely translated into significantly similar trend of data point’s distribution for experimental (ExD), derived model (MoD) and regression model-predicted (ReG) results. Methane gas yield per unit input ratio OLR/ HRT were evaluated from experimental, derived model & regression model predicted results as 1.0035, 0.9893 & 0.9574 m6 Kg -2 d2 respectively. Standard errors incurred in predicting methane gas yield for each value of OLR, HRT & OLR/HRT considered as obtained from experiment, derived model and regression model were 0.1237, 0.1032 & 0.0226%, 0.1214, 0.1055 & 0.0221 % and 0.122, 0.1032 & 2.5336 x 10-5 respectively. The operationally viable deviation range of model-predicted methane gas yield from the experimental results was 3.75-15.25 %. This translated into 84.75-96.26 % operational confidence and reliability level for the derived models, as well as 0.85–0.96 yield response coefficient of methane gas to the input ratio OLR/ HRT.

quadratic yield response methane gas input ratio of hydraulic retention time organic loading rate microbial digestion fruit wastes

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