Resource Utilization of Tea Residue Biomass via Catalytic Vacuum Pyrolysis

Waste biomass represents both an environmental pollutant and a potential renewable energy source. This study examines the feasibility of hydrogen production from tea residue biomass and solid waste, focusing on pyrolysis-based hydrogen generation. Compared to atmospheric pyrolysis, vacuum conditions reduce the saturated vapor pressure of biomass volatiles, thereby promoting char gasification, gas-phase interactions, and secondary tar cracking. Utilizing a self-designed vacuum-pyrolysis-catalysis system, we investigated the effects of key parameters—vacuum level, temperature, catalyst-to-feedstock ratio, and retention time on pyrolysis product distribution and formation mechanisms. Results indicate that Ni was successfully and uniformly loaded onto waste calcium oxide desiccant (DC) support via impregnation, thereby significantly increasing the specific surface area of the catalyst. Optimization using response surface methodology identified the following optimal conditions: pressure of 5 kPa, temperature of 835.89 °C, catalyst/feedstock ratio of 110.02%, and retention time of 2.35 h. Under these conditions, a hydrogen yield of 256.39 mL·g−1 was achieved, corresponding to 95.3% of the simulated value. The process not only enabled efficient hydrogen production but also simultaneously yielded bio-oil and biochar, thereby facilitating carbon capture and recycling. These findings provide valuable insights into the resource-oriented application of vacuum pyrolysis-catalysis technology to waste biomass.