Ethanol Production from Vineyard Pruning Residues with Steam Explosion Pretreatment

Second generation bioethanol is a renewable fuel that can be produced from cellulosic biomass through hydrolysis and fermentation based processes. Vineyard pruning residues constitute a potential lignocellulosic substrate for bioethanol production, since they have high sugar content and are a renewable, cheap, and readily available feedstock. In this work, vineyard pruning residues were firstly characterized to determine the content of ash (3.060.0%), extractives (12.260.0%), acid insoluble lignin (31.662.2%), glucan (28.460.9%), XMG (14.460.4%), arabinan (2.660.2%), and acetyl groups (3.960.8%) using the standard laboratory analytical procedures for biomass analysis provided by the National Renewable Energy Laboratory. Vineyard pruning residues were then pretreated in a steam explosion pilot unit at severity of 3.83, 4.24, 4.56, and 4.69. The two pretreated water insoluble fiber fractions, characterized by the highest cellulose recovery yield, were tested for ethanol production by separate hydrolysis and fermentation process. The composition of pretreatment products, the enzymatic digestibility, and the ethanol yield were analyzed. Results show that the maximum ethanol yield (8.9 g ethanol/100 g raw material) is obtained after pretreatment at a severity of 4.24.