Transpirational drying effects on energy and ash content from whole-tree chipping operations in a southern pine plantation
Newly announced North American bioenergy projects will likely increase the demand for woody biomass substantially over the next five to ten years. High harvesting and transportation costs for woody biomass from forests are commonly identified as key constraints to expanding this new industry and meeting expected wood fiber demand. In addition to a cost-competitive feedstock, wood energy facilities prefer drier raw material to maximize energy content and cleaner material with less dirt or grit to minimize the ash remaining after combustion. We examined extended transpirational drying times of felled trees to study their correlation with moisture, ash, and energy content. We compared production rates and material properties for three drying treatments of felled trees in a 14-year old planted loblolly pine stand: (1) drying in the field for approximately eight weeks, (2) drying in the field for approximately four weeks, and (3) freshly felled (or green) trees. A range of operational variables including fuel consumption, knife wear, chipper productivity, the number of stems per linear foot of trailer, and tons per linear foot of trailer were also compared.