Evaluation of the Steam Explosion Pretreatment Upon the Anaerobic Digestion of Water Hyacinth Biomass: Influence on Liquid and Solid Fractions

Abstract

Biochemical methane potential tests were performed to evaluate the effects of steam explosion on the liquid and solid substrates of thermal hydrolysis pretreatment applied to water hyacinth biomass. The operational conditions of the thermal hydrolysis applied the combination of two temperatures (170 and 210 ºC) and two cooking times (5 and 30 min). The higher solubilization factor was 22.9% for the sample pretreated at 210 ºC and 30 min followed by steam explosion effect (TH + SE). Steam explosion, temperature and time were, in order of importance, the more effective operational conditions for the biomass solubilization. The sample 210 ºC - 5 min TH + SE presented the higher methane production increase, in relation to the raw substrate, resulting in a increment factor of 2.43, for the solid sample. The higher methane production increase for the liquid sample was on a factor of 1.67, for sample 210 ºC - 30 min TH + SE. The higher biomethanization increase considering both biomass factors (solid + liquid) was obtained for the pretreatment 170 ºC - 30 min TH + SE. A combined model confirmed the hydrolysis limitation for the solid samples biodegradation; however, it was not clear for the prediction on the liquid samples. Micrographs evidenced the morphological changes of the solid substrate with the solubilization increase. Particle size reduction was the most effective effect of the pretreatment on the substrate morphology. Porosity increment was observed only in the surface of the sample 210 ºC - 30 min TH + SE