Wood fuel powders cut in different mills were combusted in a 150 kW burner to study emissions, furnace temperature and burnout as a function of particle size distribution and particle shape. Particle characteristics only slightly influenced NO, formation but more strongly influenced fuel feeding, ignition, unburned pollutants and furnace temperature. The lowest NO, emissions achieved was < 50 mg/MJ. For finely milled wood powder, CO emissions had the lowest values (21 mg/MJ). Varying the ratio between primary, secondary and tertiary airflows, slightly influenced the combustion results using a small-scale powder burner. (C) 2003 Elsevier Ltd. All rights reserved.