The effects of furnace sorbent injection on waste characteristics and the performance of electrostatic precipitators (ESPs) have been studied under conditions simulating full scale operation at Ontario Hydro's 640 MJ/h Combustion Research Facility. Twice as much waste was produced as with coal ash; the waste was found to contain high levels of calcium compounds (CaO, CaSO4, etc.). In situ resistivity and impactor data were obtained using various sorbents injected either as a dry powder or in the form of a slurry while burning coals with sulphur content ranging between 1.4 to 2.8%. Resistivities were found to increase 2- to 3-orders of magnitude from a baseline level of 108 ohm.cm, and the size distribution of particles suspended in the flue was slightly finer than the baseline ash. Experiments with flue gas conditioning showed that the resistivity of the ash/sorbent mixture produced from limestone injection could be reduced by 1- to 2.5-orders of magnitude during SO3 conditioning and 3-orders of magnitude during water conditioning. Both agents improved the performance of the ESP and reduced particulate emissions by a factor of 1.2 to 4.