Characterization of Coal Tailings from Indiana—Implications for Their Potential Utilization as Sources of Critical Elements and Carbon

The purpose of this study is to characterize coal tailing deposits in Indiana as potential sources of critical elements and carbon. Samples of coal tailings were obtained from two deposits of two former preparation plants: one in Greene County that processed the Tradewater Formation (mostly former Brazil Formation) coals and the other one in Pike County that processed exclusively the Springfield Coal of the Petersburg Formation. The idea before selection of these two sites was to compare coal waste from different coal types: the high-sulfur Springfield Coal and the relatively lower-sulfur former Brazil Formation coals. The characterization is based on the analysis of 33 samples from the Greene County site and 42 samples from the Pike County site. Average carbon, sulfur, and ash contents for the Greene County tailings are 52.0, 2.7, and 35.0 wt %, respectively, in comparison to 73.3, 5.6, and 33.8 wt % in the Pike County tailings. On ash basis, the Greene County tailings have larger concentrations of arsenic (As) (89.5 ppm), cobalt (Co) (60.9 ppm), gallium (Ga) (32.9 ppm), and germanium (Ge) (50.2 ppm) than those in the Pike County tailings (51.7, 19.9, 29.6, 35.7 ppm, respectively). REE+Y+Sc concentrations are also higher in the Greene County tailings, both on ash basis (475.4 versus 413.3 ppm) and whole-rock basis (164.7 versus 130.8 ppm). The coal tailings from Pike County are vitrinite-rich (73.7 vol % on average), whereas those from the Greene County have less vitrinite (47.7 vol %) and more inertinite (47.7 vol %), consistent with the differences in the petrographic composition of the original coals processed at these locations.