The influence of particle size on biomethanation: a study of Eichornia crassipes biomass (water hyacinth) from the Lower Volta River in Ghana using fruit waste sludge as inoculum source

Abstract

The study focused on the impact of particle size on methane and biogas production by digesting water hyacinth biomass as substrate and fruit waste sludge inoculum for 110 days under mesophilic conditions. A modern BlueSens laboratory-scale anaerobic digestion equipment was employed for the experimental work which focused on four distinct particle size ranges: 0.25–0.09 mm (F2), 0.60–0.30 mm (F3), 1.71–0.71 mm (F4), and 4.75–2.00 mm (F5). The finest particles in F2 recorded the highest methane yield of 4215.2 ml (334.54 ml CH₄/gVS) which was approximately 2.4 times greater than the yield from the largest particle sizes in F5 which measured 1747.3 ml (138.67 ml CH₄/gVS). Similarly, the maximum biogas production (6452.14 ml) occurred in F3, followed by F2, F4, and F5. When the experimental methane yield data was fitted into the modified Gompertz model equation, the smallest particles (F2) exhibited a maximum methane production rate of 75.44 ml CH₄/gVS day, approximately 1.6 times faster than the rate of the largest particles (F5). The lag phase was absent in F2 and F3 which indicated instantaneous methane production at the start of the fermentation process. In contrast, F5 experienced the longest lag phase of 13 days, indicating the influence of particle size on the duration of lag phase. The experimental data simulation using the first-order kinetic model showed that, except for F5, the hydrolysis rate constant values for the remaining test fermenters had a negative correlation with their respective methane yields. Overall, these findings indicate that smaller particle sizes offer a larger surface area which facilitates microbial-substrate interactions to promote biodegradation process.