The fundamentals of ignition, NOx (NO and N2O) emissions, and ash formation characteristics for biomass and mixtures of coal with biomass are precisely elucidated in this study. In this study, biomass, coal, and a biomass-coal mixture are burned, using an electrically heated drop tube furnace. In the combustion test, the focus is on the ignition behavior, combustion efficiency, NOx emission behavior, and formation characteristics of particulate matter, based on the results of gas compositions along the furnace axis and a collection of particulate matter by a low-pressure impactor. As a result, the addition of biomass into low-rank coal affects combustion behavior, especially for ignition enhancement. The NO and N2O concentrations in co-combustion are almost the same as those in coal combustion, even if the quantity of input fuel nitrogen under the co-combustion condition is half of that under the coal combustion conditions. A kinetic simulation of the NO and N2O behavior results is conducted, using the homogeneous reaction schemes at constant temperature. The simulation result of NO concentration agrees with the experimental result obtained. However, the N2O concentration calculated is less than the experimental result, because the heterogeneous schemes that are related to N2O are not considered in this simulation. Fine particulates with a size of < 2 mu m during biomass combustion are produced. Burning the biomass with coal shifts the particle size distribution from fine particles to coarse particles, which can be captured by dust collection systems.