Identifying contaminants of coal-derived inertinite in charcoal briquettes : Preliminary findings of microscopic analysis

Despite the widespread popularity of charcoal-based grilling fuels, extensive studies have highlighted various pollutants linked to their production and combustion, posing potential risks to human health and the environment. Since the presence of impurities has been identified as a factor contributing to elevated emissions of harmful gases and particulate matter, a comprehensive quality assessment of grilling fuels is imperative to effectively manage and minimise potential risks to customer health and safety. While identifying many impurities in solid biomass fuels is possible through microscopic analysis, identifying fossil coal contaminants in charcoal briquettes can be challenging. The biggest difficulty arises when coal-derived inertinite and man-made charcoal need to be distinguished as both exhibit numerous visual similarities in microscopic images. Therefore, the goal of this study was to examine the optical morphology of inertinite and charcoal with the aim of differentiating them when they co-occur in charcoal briquettes. The results show that employing high differential interference (DIC) and fluorescence filters, coupled with reflected white light in microscopic analysis, can enhance the observations allowing for easier detection of impurities of inertinite in charcoal-based grilling fuels. Among the most notable distinctions are the high degree of cellular structure preservation and the presence of small pores and protrusions in man-made charcoal; these characteristics are typically absent in the inertinite fragments.