Tuesday, May 3, 2011
Second generation bioethanol, from lignocellulosic biomass, holds promise for conservation of crude petroleum and obtaining energy security. Cellulose, the most abundant constituent of lignocellulosic biomass can be converted into fermentable sugars for production of ethanol. Different forestry products and residues, agricultural byproducts, grasses, food processing and municipal solid wastes can serve as lignocellulosic feedstock. Among forestry resources, fast-growing, drought-resistant Populus deltoides, cultivated in short cycles, promises to be a sustainable feedstock. Poplar wood has about 44% cellulose, 15% xylose and 28% lignin. Pretreatment of lignocellulosic biomass and subsequent enzymatic hydrolysis of cellulose to fermentable sugars are the main cost intensive steps in biomass to ethanol process. Amongst the existing pretreatment technologies, dilute acid pretreatment is preferred as it removes a large fraction of xylan and opens pores for facilitating attack of enzyme on cellulose.
The present study was conducted to evaluate the saccharification efficiency of high and low specific gravity hybrid Poplar wood, pretreated with dilute sulfuric acid, at 5% wt/vol loading at 160⁰ C for 60 min in a fluidized sand bath. This led to high recovery of xylan as xylose. Glucose and furfural were also detected in these extracts. After water-washing this pretreated biomass, enzymatic hydrolysis was performed using Accellerase® 1500 (0.5ml/g biomass) at 55⁰C. This process yielded the highest glucose levels within 24hrs. Further optimization of pretreatment temperatures and dosage of enzyme for complete saccharification will be undertaken.