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[Display omitted] • A sustainable conversion of plantation waste into syngas was achieved using CO 2 (key greenhouse gas). • CO 2 served a partial oxidant reacting with volatile pyrogenic products evolved from rubber tree residue, leading to enhancement of syngas, especially CO. • Oxidative functionality of CO 2 on syngas production was intensified in the presence of a nickel-based catalyst (Ni/Al 2 O 3). • Integrated process of catalytic pyrolysis and water–gas shift reaction notably increased H 2 productivity. This study introduces the sustainable recovery of energy from plantation waste by converting rubber tree residue (RTR) into syngas through carbon dioxide (CO 2)-assisted pyrolysis. The investigation centers on elucidating the specific impact of CO 2 on the pyrolysis of rubber tree residue, emphasizing its significant influence on enhancing syngas production. At temperatures ≥ 500 °C, CO 2 engages with volatile matters (VMs) released during the thermolysis of rubber tree residue, increasing carbon monoxide (CO) yields. To further optimize the process, catalytic pyrolysis setups incorporating additional heat (600 °C) and a nickel-based catalyst (Ni/Al 2 O 3) were implemented. These experimental configurations substantially increased syngas production from 19.51 to 24.24 mmol g−1, particularly amplifying CO yields under CO 2 conditions 2.58-fold compared to nitrogen (N 2) conditions. This enhancement is attributed to the partial oxidation of volatile matters facilitated by CO 2. Additionally, the Ni/Al 2 O 3 catalyst played a pivotal role in expediting the gas-phase homogeneous reaction of CO 2 with volatile matters, leading to further improved syngas production. Indeed, the syngas yield in the catalytic pyrolysis in the presence of CO 2 was 24.24 mmol g−1, which increased by 1.24 times in reference to the result under the N 2 environment. The identified functional role of CO 2 presents an opportunity to enhance the sustainability of waste management by optimizing carbon utilization and generating value-added products. [ABSTRACT FROM AUTHOR]