Kinetics of Diauxic Biogas Production from Energy Crops: Sunflower (Helianthus annus) and Napier Grass (Pennisetum purpureum) with Animal Manure

摘要

This study evaluated the kinetics of diauxic-like pattern of biogas production from energy crops, Sunflower (SF) and Napier grass (NG) with cow dung (CD). The tests were performed in a batch reactor (R) operation for 60 days in R1 - R4 and 53 days in R5 - R8 under mesophilic conditions (24 - 36~(O)C). The characteristics of the tested energy crops suggest that they hold prospects for bioenergy production. The cumulative biogas yield/gVS showed that the best performance was R1 with a biogas yield of 15.17 dm~(3) (0.046 dm~(3)/gVS) followed by R3, 13.90 dm~(3) (0.041 dm~(3)/gVS) and R2, 11.01dm~(3) (0.032 dm~(3)/gVS). A significant difference ( P ≤ 0.05) in biogas yield was found in the reactors charged with SF/CD as against SF only. In the reactors that exhibited biphasic biogas production profile, two (2) kinetic parameters, K1 and K2 were determined by the bi-logistic function model. It was observed that the predicted values in the second phase (K2) of biogas production were considerably higher than the first phase (K1) in R2 - R5 as opposed to R6 - R8, which implies more biogas yield in phase 2 than phase 1. The results indicate that anaerobic digestion of SF and NG had a strong positive influence on biogas yield, BP, PR and λ_(1) but not for λ_(2). The bi-logistic function model suitably fitted the experimental data with a high correlation coefficient (R~(2)) in the range of 0.986 - 0.997. Based on the kinetic parameters, the bi-logistic function model is well suited for the simulation of diauxic-like biogas production process.