Potential mercury and hydrochloric acid emissions from wood fuels

The forest products industry has a large number of wood-fired boilers that will have to meet new EPA emission limits for mercury and hydrochloric acid (HCI). The emission standards are 9 lb./10(12) Btu heat input for mercury and 0.09 lb./10(6) Btu heat input for HCI, although boilers built after January 2003 have to meet more stringent limits of 3 lb./10(12) Btu for mercury and 0.02 lb./10(6) Btu for HCI. Demonstrating compliance with these limits requires fuel analysis and stack testing. However, stack testing is not necessary if it can be shown that the fuel has sufficiently low concentrations of mercury and chlorine such that emission limits would be met even if all the mercury is emitted and all the chlorine is emitted as HCI upon combustion of the fuel. Analysis of bark and stemwood samples collected at 30 locations across the United States gave averages of 1.42 lb./10(12) Btu and 0.28 lb./10(12) Btu for mercury in bark and stemwood. Based on these results, bark and stemwood fuels have potential mercury and HCI emissions considerably lower than the EPA limits for existing boilers.