This is a photo of an electrostatic precipitator (ESP) which is being installed as a key part of Gundersen’s biomass boiler project. An ESP is used to remove small particles, called particulates, from the flue gas (exhaust) as it flows into the stack. Combustion processes, which are needed in northern climates to provide heating, create various levels of emissions. Electrostatic Precipitators are considered to be the “gold standard” for removal of particulate emissions that can be harmful to health and the environment. ESPs are also relatively energy efficient and remove particles from the flue gas with minimal parasitic electricity loads to the operation. Other technologies that are used to remove particulates are bag houses, cyclonic separators, and wet scrubbers. Each technology has advantages and disadvantages but ESPs are still considered among the best methods.
Other steps Gundersen has taken to minimize emissions as part of the biomass boiler project are to utilize a cyclonic separator, install automated emissions monitoring equipment, and maintain a very tight specification on biomass fuel quality. The choice of fuel is another key factor in whether or not a combustion process has safe emission levels or problematic emissions. The biomass fuel for this project will be wood chips from a local, hardwood lumber mill. The fuel specification prohibits wood that includes treatments such as paints, glues, varnishes, heavy metals, or other plant materials. Clean, dry, organic hardwood has excellent thermal energy per pound and can be combusted quite cleanly with the proper systems. Thorough combustion of a good fuel also minimizes emissions. Frequent emissions monitoring and Wisconsin Department of Natural Resources testing will also ensure that regulatory permit standards are met. This renewable energy project will produce roughly 38% of Gundersen’s energy needs, provide a substantial fuel savings, and reduce its dependence on fossil fuels.