CO₂-cofeeding catalytic pyrolysis of macadamia nutshell

Here in this study, we laid great stress on a development of sustainable waste-to-energy (WtE) platform via CO₂-cofeeding catalytic pyrolysis of macadamia nutshell (MNS) at mild temperature region. To this end, one-stage and two-stage (non-catalytic/catalytic) pyrolysis of MNS was performed to establish the fundamental relationship of temperature effect on syngas formation. The formation of gaseous pyrolysates was substantially enhanced when two-stage pyrolysis of MNS was applied, and second heating zone isothermally ran at 700 °C. Such the enhanced generation of gaseous pyrolysates from two-stage MNS pyrolysis of MNS was likely due to temperature-driven cracking of volatile organic compounds (VOCs). Also, catalytic two-stage pyrolysis of MNS was performed at lower isothermal running temperature (500 °C) over Ni/SiO₂ and Co/SiO₂. The enhanced formation of syngas (H₂ and CO) was observed from catalytic pyrolysis of MNS. Therefore, pyrolysis of MNS over Ni/SiO₂ or Co/SiO₂ could be a reliable platform for enhancing syngas formation at mild temperature (≤ 500 °C) under CO₂ environment. In addition, all experimental findings suggested that the use of CO₂ is beneficial in the WtE platform, and the use of CO₂ could be a practical climate change mitigation measure.