Samples of the different fuels that was used in the combustion tests were collected in a plastic bag and the moisture content was analysed according to EN 14774-1[13]. The actual humidity ratio was used to recalculate the heating value of the fuels depending on the humidity level. Analysis of the remaining ash according to EN 14775-1[14] was used to determine the amount of unburned carbon which was left in the ash box after each experiment.