Supercritical water Co-gasification of biomass and plastic wastes for hydrogen-rich gas production using Ni-Cu/AC-CaO catalyst

Supercritical water gasification (SCWG) of sugar beet pulp (SBP) as lignocellulosic biomass and high-density polyethylene (HDPE) as plastic waste to produce hydrogen-rich gas is investigated. Factors affecting SCWG of SBP were investigated by experimental design method. The variable parameters included temperature (385–460 °C), reaction time (10–30 min) and feedstock concentration (0.25–3.25 wt%). 460 °C, 30 min and 1.04 wt% were identified as optimal points for the highest hydrogen yield. SCWG of SBP and HDPE blend with different ratios were carried out to investigate the synergetic effect of blending on the efficiency of total gas and hydrogen yields. Hydrogen production increased with increasing the ratio of HDPE in the feedstock mixture and reached its maximum of 8.95 mmol/g at the ratio of 40 wt% and then started to decrease. Using a low-cost catalyst (Ni–Cu/AC-CaO) for SCWG of blended feedstock enhanced the total gas and hydrogen yields by factors of 2.4 and 3.8, respectively.