Coke production is expensive and requires stringent environmental controls. Pulverized coal injection (PCI) is effective in reducing blast furnace coke consumption however when injected at high rates it can lead to the accumulation of unburnt char. This study consisted of an investigation of four different North American coals, Fording, Thacker, Chisholm, and Pinnacle together with Japanese Cypress wood chips charred at various temperatures for different times in order to establish a fundamental understanding of the relationships between char structure and its influence on char reactivity. It was found that as char crystallinity increased, its reactivity decreased. Fording char was found to be 67% more reactive than Pinnacle char, and 47% more reactive than Thacker char. Graphite was the least reactive of the samples tested. On the other hand, Japanese Cypress contained a small amount of hydrogen and considerable oxygen, and formed nongraphitizing char structures that were highly reactive.