Chemical Pretreatment of Lignocellulosic Biomass for Utilization as Feedstock for Fuel and Chemical Production through Biochemical Processes

Abstract

A local lignocellulosic biomass from an industrial vegetable processor was chosen as the subject of HCl and KOH pretreatment studies. The biomass contains ~80% green onion and a consortium of celery, pepper, and carrots. The vegetable waste contains about 5.7 wt.% cellulose, 83.8 wt.% hemicellulose, and the remaining were most probably lignin.

The HCl study indicated that sugar concentration is highly affected by the presence of other compounds. An optimum condition was identified at 50°C and 3.5 wt.% HCl. A kinetic study indicated that the pretreatment is complete after 30 minutes and produced a hydrolysate containing 15.05 ± 1.19 g/L glucose, 28.12 ± 2.22 g/L xylose, 4.90 ± 0.69 g/L lactic acid, and 3.22 ± 2.08 g/L propionic acid, and a yield of 0.65 ± 0.05 gram of sugar per gram of solid vegetable waste.

The KOH study yielded an optimum condition at 150°C and 3.5 wt.% KOH. A kinetic study indicated that the pretreatment is complete within 30 mins. It produced a hydrolysate containing 38.14 ± 0.63 g/L glucose, 12.17 ± 0.24 g/L xylose, 5.26 ± 0.11 g/L arabinose, 42.06 ± 6.51 g/L lactic acid, and 24.29 ± 3.22 acetic acid, and a yield of 0.82 ± 0.02 gram of sugar per gram of solid vegetable waste.

A study for the CaO catalyzed hydrolysis of cellulose was also conducted. The study determined an optimum condition of 138°C, 1.7 wt.% CaO and 17.8 wt.% cellulose with hydrolysate concentrations of total sugars, and organic acids at 79.86 ± 12.97 g/L and 31.40 ± 3.40 g/L, respectively. No inhibitors were detected. Fructose was also present in the resulting hydrolysate. A kinetic study indicated that the pretreatment is complete within 50 minutes. A yield of 0.76 ± 0.02 sugar per gram of cellulose was obtained.