CRADLE-TO-GATE LIFE CYCLE ASSESSMENT OF SWITCHGRASS FUEL PELLETS MANUFACTURED IN THE SOUTHEASTERN UNITED STATES

摘要

Developing renewable energy sources with low environmental impacts is becoming increasingly important as concerns about consuming fossil fuel sources grow. Cultivating, harvesting, drying, and densifying raw biomass feedstocks into pellets for easy handling and transport is one step forward in this endeavor. However, the corresponding environmental performances must be quantified. This study presents cradle-to-gate life cycle inventory and impact assessment data for switchgrass fuel pellets potentially manufactured in the US Southeast. Because there are no current manufacturers of switchgrass pellets, inventory data were based on field trials of cultivation and harvest of switchgrass combined with a separate study of wood pelletization. Energy inputs for cultivation and harvest of switchgrass were collected by survey from farmers in Tennessee and represent the years 2008, 2009, and 2010. Data for pelletization were taken from a report on wood pellet manufacturing in the US Southeast. To produce 1.0 Mg of pellets that contain 18.0 GJ of potential bioenergy, 4.1 GJ of fossil energy inputs were required. Switchgrass crops require relatively little energy and inputs for the cultivation and harvest processes. The majority of the environmental burdens are associated with drying and pelletizing the raw material.