Pilot scale dilute acid pretreatment of rice straw and fermentable sugar recovery at high solid loadings

The aim of this work was to study the dilute acid pretreatment of rice straw (RS) and fermentable sugar recovery at high solid loadings at pilot scale. A series of pretreatment experiments were performed on RS resulting in >25 wt% solids followed by enzymatic hydrolysis without solid-liquid separation at 20 and 25 wt% using 10 FPU/g of the pretreated residue. The overall sugar recovery including the sugars released in pretreatment and enzymatic hydrolysis was calculated along with a mass balance. Accordingly, the optimized conditions, i.e. 0.35 wt% acid, 162 °C and 10 min were identified. The final glucose and xylose concentrations obtained were 83.3 and 31.9 g/L respectively resulting in total concentration of 115.2 g/L, with a potential to produce >50 g/L of ethanol. This is the first report on pilot scale study on acid pretreatment of RS in a screw feeder horizontal reactor followed by enzymatic hydrolysis at high solid loadings.