Sulfate emission measurements were conducted on a hog-fired boiler. The boiler utilized both hogged bark and No. 6 residual fuel oil in various usage ratios. Sampling was conducted both at the boiler outlet and at the particulate control device outlet using a total sulfate sampling train. The sulfate emissions were proportional to the combustion of the residual fuel and were not influenced by the presence of hogged fuel. The work also indicated that sulfates are partially controlled by the condensation of sulfuric acid prior to the particulate control device.