Cradle-to-Gate Life-Cycle Inventory and Impact Assessment of Wood Fuel Pellet Manufacturing from Hardwood Flooring Residues in the Southeastern United States

In this article, we present cradle-to-gate life-cycle inventory (LCI) data for wood fuel pellets manufactured in the Southeast United States. We surveyed commercial pellet manufacturers in 2010, collecting annual production data for 2009. Weighted-average inputs to, and emissions from, the pelletization process were determined. The pellet making unit process was combined with existing LCI data from hardwood flooring residues production, and a life-cycle impact assessment was conducted using the Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI) model. The potential bioenergy and embodied nonrenewable energy in 907 kg (1 ton, the functional unit of this study) of wood fuel pellets was also calculated. The pelletization of wood requires significant amounts of electrical energy (145 kWh/Mg), but the net bioenergy balance is positive. Wood pellets require 5.8 GJ of fossil energy to produce 17.3 GJ of bioenergy (a net balance of 10.4 GJ/Mg). However, if environmental burdens are allocated to the pellet raw material (flooring residues) by value, then the embodied fossil energy is reduced to 2.3 GJ. The pelletization unit process data collected here could be used in an assessment of the environmental impacts of pellet fuel, or when pellets are a pretreatment step in wood-based biorefinery processes.