Plasma pyrolysis for valorizing petrochemical residues: Technical advances, commercial pathways, and circular economy integration — A critical review

Abstract

The global energy system remains heavily dependent on fossil fuels (86.6% of 592 EJ in 2024), creating an urgent need to mitigate hazardous refining residues. This critical review evaluates plasma pyrolysis as a potential decarbonization tool that converts these wastes into valuable products with minimal emissions. Thermal plasma achieves > 99% volume reduction via extreme temperatures in laboratory studies, while non-thermal plasma (NTP) consumes up to 95% less energy (referring to discharge power in laboratory-scale methane studies; this advantage has not been validated for liquid residue feedstocks) while producing hydrogen and carbon materials. The oxygen-starved environment eliminates most toxic emissions, enabling near-zero direct CO₂ hydrogen production, though NOx from fuel-bound nitrogen remains possible. For liquid refinery residues, no direct energy efficiency comparison between NTP and thermal plasma exists in the peer-reviewed literature; all reported advantages for NTP are extrapolated from methane or light hydrocarbon studies. Hypothesized NTP energy efficiency advantages in laboratory settings (for methane/light feeds) translate to an estimated 30–50% lower capital costs than thermal alternatives in conceptual studies that assume methane-like feedstocks and have not been validated for heavy residues, with co-produced hydrogen adding an estimated $25–50 per ton of carbon black in revenue for typical heavy residues (assuming 0.05–0.10 kg H₂/kg CB at $3000–5000/t H₂). Coupling with renewable microgrids could theoretically achieve 90–95% clean energy penetration in favorable locations, reducing carbon intensity by over 90% and positioning plasma pyrolysis as a dispatchable load for grid stabilization — though no such integrated facility has been demonstrated. An illustrative calculation for a conceptual 50,000 t/yr facility suggests it could avoid approximately 172,500–290,000 t CO₂e annually under a single illustrative baseline (e.g., displacing landfill, conventional carbon black, and SMR hydrogen; these figures are highly speculative and depend on multiple assumptions not validated commercially). Compared to molten metal, catalytic, and electrochemical alternatives, plasma technology offers distinctive feedstock flexibility for refinery integration, but no commercial-scale facility processes liquid refinery residues via plasma pyrolysis; the technology readiness level remains at TRL 4–6 (laboratory to pilot demonstration) for this specific application. By synthesizing process efficiencies, life cycle assessment, and techno-economic analysis with appropriate caveats, this review demonstrates that plasma pyrolysis serves as a promising bridge between today's hydrocarbon economy and a low-carbon, materials-focused circular future — provided that substantial technical and economic hurdles can be overcome at commercial scale.