Biomass Burning Alternatives - Tub Grinder

This page last reviewed July 7, 2008

When Whole Tree or Cut to Length logging operations are processing sawlogs only, large delimber or "slash" piles are created from the material that does not make a sawlog. A tub grinder can turn these large piles into biomass chips for delivery to cogeneration plants or landscape mulch producers. In addition, there is usually material left over from a biomass operation which is too small to be processed through a chipper, but which can be processed with a tub grinder.

The stand condition description used for whole tree and cut to length logging operations applies to tub grinding, since the slash piles are a byproduct of those operations. Chaparrals and other brush species can also be managed with a tub grinding operation.

Equipment Needed for Tub Grinding Operations:
  • Tub Grinder for chipping piles
  • Tractor to move slash piles around
  • Loader to put slash into tub grinder.
  • Chip trucks
Forest Products:
  • Biomass Chips
  • Lanscape Mulch
Cost to Produce Product:
(These costs are estimates and do not include haul costs. Actual costs may vary.)
  • Biomass Chips -- $22 to $32 per bone dry ton
    (assume 14 bone dry tons per load)
  • Landscape Mulch 
Advantages of Tub Grinding:
  • Suitable for materials that cannot be processed in a chipper
    (Example: slash piles)
  • Increased fuel removal from forest
Disadvantages of Tub Grinding:
  • Lower quality chips due to potential for rocks and dirt to be intermixed in material