Clean fuel and efficient combustion result in less than 1% ash

ImageBiomass ash 2

Gundersen Health System’s Envision® biomass boiler project is part of  its plan to lead the healthcare industry in environmental stewardship and lower energy costs. Gundersen Health System is headquartered in La Crosse, Wis., with hospitals and clinics in Wisconsin, Minnesota and Iowa. For more information, call (608) 775-1400 or go to

The photo on the left shows an ash bin used to collect biomass boiler ash from Gundersen Health System’s new Biomass Boiler system. Ash is removed at a couple of points in the system after the hot flue gas leaves the combustion chamber. The first point is immediately after leaving the combustion chamber, the second point after the multi-cyclone unit, and the third point is after the Electrostatic Precipitator (ESP). At each of these points, a finer level of particulates is removed and prevented from reaching the atmosphere.

The photo on the right shows the ash within this particular bin. The small amount of dark ash in the center of the right photo was manually removed from the boiler chamber after a week of running. The light colored ash is typical of what is found at the points where removal occurs from the flue gas. The light colored ash is very fine and powdery to the touch after cooling.

The bins are made of metal and are fireproof to prevent a fire risk from the ash as it cools. These systems are automated and contained for safety. The amount of ash from the woody biomass fuel source used for Gundersen’s new boiler is less than 1%. This low amount is a result of the clean fuel specification and efficient combustion systems of the new boiler. The raw fuel specification is very stringent and only permits clean, organic sources of wood to be used as fuel. Ash from sources like this one can often be used for a soil amendment, composting amendment, or other applications to provide carbon and other nutrients used in agriculture. In some cases, it can add an additional revenue stream for a biomass project.


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