Efficacy of waste to energy ash in NOx abatement.

Abstract

This work investigates the catalytic performance of unmodified waste-to-energy (WtE) ash for nitrogen oxides (NOx) abatement via selective catalytic reduction. NOx conversions up to 44% were measured in a simulated flue gas (2,600 ppm NO, 9,700 ppm CO, 1.8% H₂O). Pretreatment substantially enhanced NO conversion relative to the as-received ash, with H₂ pretreatment yielding up to 91% conversion. Characterization revealed a low surface area (17.8 m² g^-1), SiO₂-CaO-Al₂O₃ matrix, and trace Fe, Mn, and Cu. Temperature-programmed reduction and thermal analysis indicated redox-active, non-metallic species. Additional spectroscopic analysis indicates temperature-dependent evolution of surface species under reaction conditions, consistent with an oxygen-mediated redox contribution to NO reduction. However, the active intermediates and specific reaction pathway remain to be fully resolved. These findings demonstrate that WtE ash, an abundant industrial byproduct, can be repurposed as a low-cost, harsh-environment catalyst for NOx abatement.Implications: This study shows that municipal waste-to-energy ash can catalytically reduce NOx at temperatures relevant to real-world flue-gas conditions, offering a potential low-cost alternative to conventional SCR catalysts. Because the material is already generated at scale, its catalytic behavior presents a new opportunity for emissions control strategies that integrate waste-derived resources and support circular-economy objectives. These findings may inform future technology development, regulatory evaluations, and research into waste-based materials for air-pollution mitigation.