Multi-analytical characterization of oxide deposits in landfill gas engines: linking elements to gas composition

Landfill gas (LFG) is primarily composed of CH₄ and CO₂, together with a wide range of trace compounds generated during the decomposition of domestic waste in landfills. During energy production from LFG, trace compounds such as sulfur-containing compounds and siloxanes cause the formation of metal oxide-based deposits. However, studies integrating gas composition with deposit chemistry, phase identification, and multi-technique validation on the same samples remain limited. This study aims to establish the linkage between LFG composition and deposit formation, focusing on the transformation of organometallic compounds into oxide phases. A multi-analytical approach including scanning electron microscopy with energy-dispersive spectroscopy, X-ray diffraction, inductively coupled plasma optical emission spectroscopy, wavelength-dispersive and energy- dispersive X-ray fluorescence was applied to characterize deposits collected from engine components. In addition to the organometallic compounds identified in standard LFG analyses at the study site, other compounds reported in the literature and detected through gas analysis were also considered. The results demonstrate that Si and S are directly associated with LFG constituents, while Ca is linked to lubricant oil additives, and metal(loid)s (Sb, Sn, As) are related to organometallic compounds present in LFG. A broad spectrum of trace elements was identified, providing comprehensive elemental coverage and highlighting potential occupational health risks associated with elements such as As, Cr, Ni, Ba, Zn, and Zr. By integrating gas composition, and deposit chemistry, this study provides new insights into deposit formation and supports the development of improved gas quality control strategies and mitigation approaches for both engine performance and health protection.