Thermochemical conversion of waste biomass via pyrolysis-gasification with enhanced post-situ CO2 capture

The integration of biomass thermochemical conversion with carbon dioxide capture offers a promising approach for simultaneously valorising agricultural waste and reducing CO 2 emissions. However, the long-term performance of catalytic pyrolysis-gasification systems combined with post-situ CO 2 adsorption remains insufficiently investigated, particularly with respect to catalyst and adsorbent regeneration. In this study, maize agricultural waste (5 g) was utilized to catalytic steam pyrolysis-gasification using Ni/ZSM-5 (2.5 g) and Ni/Clinoptilolite (2.5 g) catalysts, followed by post-situ CO 2 adsorption using clinoptilolite (30 g). The effects of the first reactor zone temperature (400 and 800°C) and ten consecutive catalyst/adsorbent regeneration cycles on gas composition, syngas yield, and CO 2 removal were investigated. At 800°C, the syngas yield reached 74.3 mmol/g feedstock for both catalysts, while the average H 2 /CO ratio increased to 0.34 and 0.35 for Ni/ZSM-5 and Ni/Clinoptilolite, respectively. The application of post-situ clinoptilolite reduced the CO 2 content by nearly half compared with the corresponding catalytic gasification results without post-situ adsorption, while increasing CO and H 2 contents by up to 20-60% and 25-65%, respectively. Compared with the baseline measurements, syngas yield increased by 68-160% at 400°C and by 10-53% at 800°C. The CO 2 reduction reached 94-100% across the regeneration cycles; however, the adsorption performance gradually deteriorated with repeated regeneration, indicating the effect of thermal stress on the adsorbent structure. Overall, the results demonstrate that post-situ clinoptilolite adsorption can effectively enhance syngas production while substantially reducing CO 2 emissions during catalytic biomass gasification, although adsorbent stability remains an important consideration for long-term operation.