The article discusses a method to determine how much nitrogen in coal contributes to N2O formation during combustion. By conducting separate combustion experiments for coal and char from the same coal, researchers can calculate the relative contributions of volatile-N and char-N. The temperature at which char is prepared and the equipment used can affect the results. It is important to use the same temperature for char preparation and combustion experiments, as well as the same equipment. The percentage of nitrogen retained in char can vary with devolatilization temperature. Char formed during coal combustion may have different properties than char prepared by coal pyrolysis.