Characterization and compositional analysis of agricultural crops and residues for ethanol production in California

This study was carried out in order to analyze characteristic and composition of crops, crop wastes, and residues including a variety of sugar beets and melons, tomato, Jose tall wheatgrass, wheat hay, and wheat straw in California. Ethanol potential was estimated from different scenarios in using carbon sources of feedstock during fermentation, including the new information of using pectin–derived galacturonic acid for ethanol production. Sugar beet appears more favorable than other feedstocks because of its high sugar content (67–75% dry basis, db) and the highest crop yield, resulting in the greatest ethanol potential of 591 m³ Gg⁻¹ db when all carbohydrates are used during fermentation, with the California area–based potential of 1273 m³ km⁻². Fermentation of polygalacturonic acid can increase the ethanol potential of sugar beet leaves up to 30% over the fermentation of hexoses alone, increasing the theoretical ethanol potential to 340 m³ Gg⁻¹ and the area–based yield of 497 m³ km⁻². Melons and tomato containing 42–69% by mass of soluble sugars showed ethanol potentials in a range of 448–545 m³ Gg⁻¹ db and the area–based yield of 25–53 m³ km⁻². The theoretical ethanol yield from lignocellulosic feedstocks tested can be maximized up to 470–533 m³ Gg⁻¹ db and 291–300 m³ km⁻² when the primary components from cellulose (27–39% db) and hemicellulose (26–30% db) are utilized. The information on composition and ethanol potential is important for determining biofuel feedstock and developing technology for efficient use of bioresource.