Unlocking the Reactive Role of CO₂ in the Pyrolysis of Heterogeneous Agricultural Residues: A Mechanistic Study and Predictive Modelling for Biorefinery Technologies

Objectives This study presents a systematic investigation into the pyrolysis of thirteen heterogeneous agricultural residues, categorised as cereal straws, high-lipid fruit seeds, and agro-industrial byproducts, across a temperature range of 300–800°C. The influence of feedstock physicochemical architecture and carrier gas environment (inert N₂ vs. reactive CO₂) on product distribution, elemental partitioning, and biochar quality was evaluated through proximate and ultimate analyses, scanning electron microscopy (SEM) with topographical intensity mapping, and multivariate statistical synthesis including Principal Component Analysis (PCA) and Pearson correlation mapping. Material and Methods The pyrolysis of 13 diverse biomass residues was investigated across 300–800°C. The influence of feedstock architecture, reactor geometry, and carrier gas environment (N 2 vs. CO 2 ) was systematically evaluated using multivariate statistical synthesis, SEM-topographical mapping, and predictive modeling algorithms. Results This demonstrates that feedstock composition fundamentally governed conversion pathways: high-volatile date seeds achieved the maximum bio-oil yield of 68.0 wt.%, while high-ash rice straw favored solid-phase carbonisation. Substituting inert N₂ with reactive CO₂ during rice straw pyrolysis facilitated the thermal cracking of tarry surface deposits, significantly enriching the biochar carbon content from 45.33% to 50.94% and enhancing pore accessibility. A suite of predictive linear regression models was developed, achieving exceptional accuracy for energy density forecasting (R 2 = 0.995) based on initial biomass characterisation. This integrated framework, combining Carbon Capture and Utilization (CCU) via CO₂-assisted pyrolysis with high-precision predictive modeling, provides an actionable, scalable platform for automated, decentralised waste-to-energy biorefineries. Conclusion Integrating Carbon Capture and Utilization (CCU) strategies via CO2-assisted pyrolysis enhances biochar quality. Combined with high-precision predictive modeling, this presents a scalable, automated framework for modern decentralised waste-to-energy technologies.