The economic feasibility of woody biomass harvest practices in Missouri : the cost of harvesting tops and small diameter trees

Abstract

Woody biomass materials which include timber harvest residues, such as tree tops and small diameter trees, have the potential to be an important source of renewable energy. Their use as an energy feedstock or use as an input for other products is partly dependent on whether the materials can be harvested and transported to markets in a cost-efficient manner. In order to supplement the current knowledge base on woody biomass harvest systems, two integrated harvest systems, a whole tree harvest that extracted tops and a whole tree harvest that extracted tops and small diameter trees, simultaneously harvested woody biomass and conventional solid hardwood products (SHWP) on 30 acres of Missouri forestland. A mechanized system consisting of a feller-buncher, grapple skidder, and loader was used in both harvesting systems. Activity sampling and time-in-motion data were collected on all harvest machinery to determine system efficiency. Joint cost analysis was used to separate costs associated with harvesting SHWP and woody biomass. Marginal cost analysis was used to treat the tops of SHWP that were brought whole tree to the landing as a by-product of the SHWP. A sensitivity analysis was used to test the effects of changes of different costs on the cost per green ton of SHWP and woody biomass. Total cost estimates per green ton of material delivered to the landing at a 5% interest rate were $35.25 for SHWP and $5.76 for woody biomass in the whole tree (WT) harvest and $32.82 for SHWP and $8.81 for woody biomass in the whole tree with small diameter tree (WTSD) harvest. With the addition of a chipper, woody biomass costs increased to $11.11 per green ton in the WT harvest system and $14.16 per green ton in the WTSD harvest system.