Modified Pyrolysis of <i>Erythrina indica</i> Biomass to Produce Noncondensable Gases Rich in Hydrogen and Low in Carbon Dioxide

The pyrolysis of waste lignocellulosic biomass is an effective route for solid waste management and valorization, producing py-gas, bio-oil, and biochar. Traditionally, research has focused on bio-oil production, but recent attention has shifted to upgrading noncondensable pyrolysis gas by increasing hydrogen (H2) and reducing carbon dioxide (CO2). In this study, the authors report a patented modified pyrolysis (MP) process for converting waste Erythrina indica (known as Indian coral tree) biomass at 600–800 °C for 2 h using Ni/Al2O3 and zeolite Y-hydrogen catalysts. Noncatalytic and catalytic experiments were performed in both closed and continuous-open modes. Under catalytic conditions, continuous-open mode operation produced higher H2 and lower CO2 than the closed mode at 700 and 800 °C, so MP experiments were conducted in continuous-open modes. The py-gas composition was measured at 0, 1, and 2 h after reaching the pyrolysis temperature. The process generated gases containing a high vol % of H2 with moderate vol % of CH4 and CO, and a negligible vol % of CO2, demonstrating the production of a highly combustible gas with minimal or negligible CO2. The best case (MP05) achieved approximately 53 vol % H2 with zero CO2, and the corresponding product yields were approximately 35 wt % bio-oil, 22 wt % biochar, and 43 wt % py-gas using the Ni/Al2O3 catalyst. Overall, MP using Ni/Al2O3 at 800 °C for 1 h maximized H2 with near-zero CO2, producing a high heating value gas (approximately 16,000 kJ/Nm3).