Hydrolysis/dehydration/aldol-condensation/hydrogenation of lignocellulosic-biomass (corncobs) and biomass-derived carbohydrates (tapioca flour) to produce water-soluble C5–C15 compounds was developed in a single reactor system. WO3–ZrO2 efficiently catalyzed the hydrolysis/dehydration of these feedstocks to 5-hydroxymethylfurfural and furfural, while the impregnation of WO3–ZrO2 with Pd allowed sequential aldolcondensation/hydrogenation of these furans to C5–C15 compounds. The highest C5–C15 yields of 14.8–20.3% were observed at a hydrolysis/dehydration temperature of 573 K for 5 min, an aldol-condensation temperature of 353 K for 30 h, and a hydrogenation temperature of 393 K for 6 h. The C5–C15 yield from tapioca flour was higher than that from corncobs (20.3% compared to 14.8%). Tapioca flour produced more C6/C9/C15, whereas corncobs generated more C5/C8/C13 compounds due to the presence of hemicellulose in the corncobs. These water-soluble organic compounds can be further converted to liquid alkanes with high cetane numbers for replacing diesel fuel in transportation applications.