Development of a novel fractal-like kinetic model for elucidating the effect of particle size on the mechanism of hydrolysis and biogas yield from ligno-cellulosic biomass

摘要

The effect of particle size on hydrolysis and biogas production kinetics from a typical ligno-cellulosicudbiomass was assessed by studying the anaerobic co-digestion of fixed amount of rice husk and cowuddung mixture using a newly developed fractal-like kinetic model. British Standard (BS) sieves wereudused to obtain varying particles size fractions ranging from 0.150 - 0.212mm, 0.212 - 0.300mm,ud0.300 - 0.600mm, 0.600 -1.000mm and 1.000 - 1.700mm from oven dried, milled rice husk andudpulverized, dried cow dung respectively. These particle size fractions from both biomass were mixedudin a ratio of 1:1 after which, they were loaded into batch reactors and digested anaerobically atudambient conditions for 75 days. Hydrolysis of ligno-cellulosic biomass was observed to depend onudthe fractal exponent (h), which indexed the presence of inaccessible regions in ligno-cellulosicudbiomass. Also, hydrolysis was observed to depend on two other intrinsic factors that comprised of theudinitial hydrolytic rate udududud ¢oudo kudYudXudand overall affinity constant ( ) o o 71 k¢S . Larger particle size fractionsudwere associated with higher affinity but lower initial hydrolysis rate while, smaller particle sizeudfractions were associated with lower affinity but higher initial hydrolysis rate. In addition, the fractaludmodel compared favorably with the popular modified Gompertz equation.