Processing woody biomass with a modified horizontal grinder
This study documents the production rate and cost of producing woody biomass chips for use in a power plant. The power plant has specific raw material handling requirements. Output from a 3-knife chipper, a tub grinder, and a horizontal grinder was considered. None of the samples from these machines met the specifications needed. A horizontal grinder was modified to replace the teeth on the drum with chipping blades in order to process whole trees into biomass chips that met the power plant?s size specification. The study was installed on the Shoal Creek Ranger District, National Forests in Alabama, near Heflin, AL. This biomass removal project was the first step in a wildlife habitat improvement treatment to convert a 37-acre stand of off-site planted loblolly pine (Pinus taeda L.) to longleaf pine (Pinus palustris M.). The trees were 15 years old with an average dbh of 4.0 inches and average total height of 30.5 feet. The time and motion study gathered data on whole-tree processing for short fiber chips (up to ½-inch long), short fiber chips from trees that had been partially delimbed to remove needles, and long fiber chips (up to ¾-inch long). The average production rate ranged from 24.9 ? 38.2 green tons/productive machine hour (gt/pmh). A machine rate of $161.20/pmh was calculated, resulting in a cost of $4.22/gt for producing the long fiber biomass chips.