Lignocellulosic biomass consists of three main components namely hemicellulose, cellulose, and lignin; each component decomposes at different temperatures. This difference in temperatures was exploited to obtain three bio-oil fractions, herein referred to as grade-I, grade-II, and grade-III bio-oils. Grade-I, -II, and -III bio-oils were collected between the temperature ranges of 240-320, 320-450, and 450-700 degrees C respectively. The copyrolysis of raw and different torrefied bagasse with high-density polyethylene (HDPE) over ZSM-5 catalyst were investigated. The effects of bagasse torrefaction, online separation, and copyrolysis on the composition and yield of three bio-oils fractions were evaluated. The grade-I bio-oils were rich in acids compared to grade-II and -III. The maximum acid yield was 47.7% obtained from raw bagasse (RBG) and dropped to 29.3% after torrefaction of bagasse at 270 degrees C. Phenols (18.3%, RBG) and ketones (22.5%, for torrefied bagasse at 180 degrees C) were also achieved. Moreover, acids significantly dropped by 50% in grade-II bio-oils compared to grade-I bio-oils. The dominant ingredients in grade-II bio-oils were mostly ketones (26.1%, torrefied bagasse at 240 degrees C) and phenols (18.7%, torrefied bagasse at 270 degrees C (TBG(270) degrees(C))), and furans (19.3%, RBG). Besides, Polycyclic aromatic hydrocarbons (PAHs) contents were low as in grade-I bio-oils. Furthermore, grade-III bio-oils were predominantly aromatics hydrocarbons 41.09% (TBG(270) degrees(C)) and the least acidic 2.81% (TBG(270) degrees(C)) fractions among the bio-oils. The low PAHs content, the great reduction in acids content, and boosting of aromatics compounds in the bio-oils fractions represent an improvement in the bio-oils quality could be attributed to the release of hydrogen radicals from HDPE decomposition. Thus, these bio-oils fractions can be utilized as fuels itself or a supplement to fuels with little modification. Finally, a reaction mechanism for the copyrolysis of TBG/HDPE was proposed.