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. The wood manufacturing industry in the United States obtains more than 50 percent of their heat energy requirements by burning wood residues produced during production (Puettmann and Wilson 2005, Puettmann et al. 2010). The primary sources for residential heating in the United States are natural gas and electricity (US Energy Information Administration [US EIA] 2012), but firewood and wood residues are burned to supplement or even replace these energy sources in about 13 million homes. However, these wood fuels can be inconvenient to handle and store. The authors are, respectively, Doctoral Candidate, Univ. of Tennessee, Knoxville ([email protected]); Research Forest Products Technologist, USDA Forest Service, Forest Products Lab., Madison, Wisconsin ([email protected]); Research Scientist, Nisus Corporation, Rockford, Tennessee; Associate Professor and Wood Products Extension Specialist, and Associate Professor, Univ. of Tennessee, Knoxville ([email protected] [corresponding author], [email protected]); Assistant Extension Professor, Dept. of Forest Products, Mississippi State Univ., Mississippi State ([email protected]); Assistant Professor, Oregon State Univ., Corvallis ([email protected]); and Consultant, WoodLife Environmental Consulting, LLC, Corvallis, Oregon ([email protected]). Jae-Woo Kim is a former Postdoctoral Research Associate at the University of Tennessee. This paper was received for publication in February 2012. Article no. 12-00015. * This article is part of a series of nine articles addressing many of the environmental performance and life-cycle issues related to the use of wood as a feedstock for bioenergy. The research reported in these articles was coordinated by the Consortium for Research on Renewable Industrial Materials (CORRIM; http://www.corrim.org). All nine articles are published in this issue of the Forest Products Journal (Vol. 62, No. 4). Forest Products Society 2012. Forest Prod. J. 62(4):280–288.