Hydrothermal Treatment of Eucalyptus Wood for Bioethanol Production

Scientists from the Department of Chemical Engineering, University of Vigo (Campus Ourense), Spain, report the hydrothermal pretreatment of Eucalyptus wood for bioethanol production. Pretreatment is an essential step in the production of bioethanol from lignocellulosic biomass, such as wood. The objective is usually to remove the (recalcitrant) lignin layer from the biomass, and render the celluloses/hemicelluloses accessible to chemical/enzymatic attack for sugar conversion. The sugars produced are then fermented to ethanol. Hydrothermal treatment is one pretreatment option which involves the treatment of biomass with steam at high temperature and pressure. This type of pretreatment reportedly satisfies many of the requirements of an "ideal pretreatment process", among which are: (1) high recovery of hemicelluloses-derived products from the biomass, (2) limited production of undesired degradation products, such as furfural and/or 5-hydroxymethylfurfural, and (3) low corrosive property of chemicals used.

The researchers mixed the Eucalyptus wood samples at a designated water-to-solids ratio and heated the mixture under pressure under non-isothermal conditions from 190^oC to 250^oC. Results showed that hydrothermal treatment could be a suitable process for enhancing the susceptibility of Eucalyptus wood towards enzymatic hydrolysis. The conversion of cellulose to glucose was achieved for substrates treated at a maximum temperature of 210^oC. Bioethanol fermentation of the pretreated substrates by simultaneous saccharification/fermentation showed also good yields. The complete paper is published in the Bioresource Technology journal (URL above).