Conversion of agricultural residues to fuel products via supercritical fluid extraction

In this study, various agricultural residues such as wheat straw, corncob, corn stover, tobacco stalk, tobacco leaf, olive waste, walnut shell, and almond shell were subjected to supercritical fluid extraction (SFE) using acetone, methanol, and water as solvent. The highest yield (59.3%) of SFE was obtained from OW with water solvent at 678 K. While carbon content of the selected samples varies from about 41.2% to 53.6%, carbon content of the extracts from SFEs varies from 52.8% to 67.8%. The hydrogen content of the extracts varies from 6.8% to 8.8%. The oxygen content of the extracts ranges from 21.7% to 38.1%, and nitrogen content ranges from 0.4% to 2.3%. Decreases of oxygen content in the supercritical fluid extracts range from 38.9% to 13.8%. The supercritical fluid extracts were fractionated into water soluble, acetone soluble, phenolic, fatty acid, polar, nonpolar, and basic fractions.