the use of forestry residues or any biomass in the production of energy has been a topic of great discussion due to the increasing pressure to establish environmentally friendly energy production. with the current energy reform, the ontario government has taken an initiative to phase out coal fired generating stations by 2014. there is a plan to retrofit these plants to use biomass as feedstock to keep the power generating stations operational. at the atikokan generating station, the focal point of this study, approximately 500,000 bone dry tonnes (bdt) of biomass would be needed to operate at 2006 operating rates (ome 2006). this study characterises northwestern ontario tree species fuel qualities to provide information for efficient use of harvesting residues in the area. the characterisation of thermal values has been done on seven common tree species in northwestern ontario to create an area specific data base for use in energy production. the components of these trees which were sampled are foliage, branches, bole and bark at 10 cm diameter, and bole and bark at breast height (1.3 m). the seven species were sampled at two different sites, one 30 km west of atikokan and the other 50 km northeast of thunder bay. two sites were chosen to determine if geographic variation in thermal values exists in the different tree species, as well as to provide adequate amounts of information for a thorough database. to obtain a comprehensive understanding of fuel characteristics of the seven species and their components three different qualities were measured: 1) gross heat values; 2) specific gravity; and 3) ash content. the range of calorific values were found to be 18.07-26.80 mj/kg. species and component were shown to have significant effects on calorific values but sites was insignificant. the range of specific gravity was found to be 0.373-0.882. site, species and component were all found to have a significant effect on specific gravity. the range of ash content was found to be 0.13- 9.19%. site, species and component were all shown to have a significant effect on ash content percentage. moisture content of burnt standing timber is also investigated for four species in five different fire ages. it was found that moisture content ranged from 16.81 to 53.69%. both species and time since fire were found to have a significant effect on moisture content. calorific content of burnt standing timber was found to have calorific content similar to living tree.