This Woodburner Needs No Chimney !

Image Gallery Photo Courtesy of Collins Bio-Energy Co.

There's a race on to meet woodstove emissions regulations, and—as of this writing—the Collins Bio-Energy Pellefier may well be at the head of the pack.

The drive to clean up particulate emissions from woodstoves (discussed in MOTHER N0. 95) is forcing major changes in a field that's undergone little significant development since Ben Franklin's days. However, despite major efforts, attempts to make direct improvements in the combustion efficiency of cordwood-burning space heaters have been only marginally successful. In fact, some researchers have concluded that the inconsistency of the fuel makes it just about impossible to dramatically improve combustion efficiency. Consequently, most designers now use a catalytic converter—a device that burns smoke after it's been produced—to meet emissions requirements.

Collins Bio-Energy Company has taken a different approach to perfecting efficient wood combustion—one that goes to the source. The Pellefier burns 1/4"—to 1/2"—diameter pellets of compressed wood (or other combustible material) that are automatically fed by an auger from an integral fuel bin. Inside the Pellefier—which, as you can see, looks much like a regular woodstove—the pellets are gasified in a preburner and the volatile by—products are burned in a secondary combustion chamber. On the average, 95% of the pellet mass burns, and peak combustion efficiency may hit 99%.

Because the Pellefier burns so cleanly—it's the cleanest solid-fuel burner ever tested by the Oregon Department of Environmental Quality—the designers were able to include a long and convoluted heat—exchange path without worrying about creosote accumulation. The tremendous surface area inside the passage extracts 85% of the heat available, leaving a stack temperature of only 155°F at maximum burn rate.