Co-liquefaction of cotton gin trash and low-density polyethylene wastes via supercritical ethanolysis for hydrocarbon-rich oil

Abstract

Bio-oil produced from lignocellulosic biomass (LCB) offers significant advantages as a sustainable energy source for future generations. However, its low-quality demands better approaches to solve problems such as low calorific value, low stability, and high oxygen content. This study investigates the feasibility of producing hydrocarbon-rich oil through supercritical ethanolysis (scEtOH) co-liquefaction of cotton gin trash (CGT) and plastic waste. The scEtOH co-liquefaction studies were carried out using various mixing ratios of cotton gin trash (CGT) and low-density polyethylene (LDPE) at a temperature range of (240–340 °C), for reaction time (0–3 h) without catalysts. Positive effects on oil yield and higher hydrocarbon content were observed at 320 °C for 2 h with CGT/LDPE ratio of 1:2 under the optimised reaction conditions. Further co-liquefaction studies on the CGT/LDPE feedstock ratios (2:1, 1:1, 1:2) at 320 °C and 2 h showed positive synergistic effects on oil yield and the hydrocarbon content in the oil increased from 3.7 wt% to 17.2 wt% when LDPE proportion was increased from 33.33% to 66.66%. Maximum higher heating values (HHV) of 31.5 MJ/kg for oil and 42.5 MJ/kg for solid products were obtained at CGT/LDPE ratio of 1:2. Additionally, the co-liquefaction of CGT and LDPE improved the carbon content in solid products from 50.9 wt% to 85.4 wt% which can be used as a sustainable carbon resource. Our results demonstrate that the co-processing of LCB and plastic wastes through scEtOH co-liquefaction is a sustainable approach to improve fuel quality, facilitate plastic recycling, and compensate for decreased availability of biomass due to seasonal variations.