New regulations implemented by the Canadian federal government to limit greenhouse gas (GHG) emissions from coal burning power plants had sparked intense activity in the utility industry to find ways to reduce emissions. Several studies have indicated that carbon capture and storage (CCS) is not going to be economically available in the short term. Co-firing biomass appears to be an option for many of the coal-fired power plants, as Canada has a,significant amount of biomass resources. Although biomass combustion can reduce greenhouse gas emissions, it can also generate other air pollutants. To determine emission factors for co-firing biomass and coal, pilot-scale tests were performed. These tests were conducted in CanmetENERGY's 0.5 MWth pilot-scale pulverized fuel research furnace, which was configured with a dual-burner system, electrostatic precipitator, and baghouse. Gaseous emissions were recorded with two monitoring systems, and traditional methods for batch sampling of halogens, mercury, and particulate matter were implemented. Emission factors were developed for a 100% coal baseline, for two co-firing ratios of 20% and 55% biomass by heating value and biomass-only firing.