Monday, April 30, 2007

Spatial availability of crop residue biomass amenable to dry collection and storage

Ethan B. Davis, Robert D. Perlack, and Shahab Sokhansanj. Envionmental Sciences Division, Oak Ridge National Laboratory, PO Box 2008, Oak Ridge, TN 37831

The Billion-Ton resource assessment report identifies slightly more than 190 million dry tons of biomass that is currently available from croplands.  Nearly 60% of these resources are crop residues with corn stover and wheat straw accounting for 75% of the identified total. Given crop yield variability and limited collection time (usually no more than a few weeks in any particular area), long-term storage will be required if these feedstocks are to be used to meet year-round feedstock demands of biorefineries.  If crop residues are collected in a traditional bale format and stored long-term then it is critical that moisture content is low, usually no more than  about 15% (wet basis) at time of collection,  Further, the bales must be kept dry to limit bale degradation and minimize dry matter losses.  This paper attempts to identify the spatial location and distribution of crop residues that are amenable to dry bale feedstock collection and storage.  A GIS approach was used to estimate the spatial location and availability of corn stover and wheat straw residues.  Specifically, relative humidity and temperature datasets were used with equilibrium moisture equations to produce maps of crop residues moisture content at time of collection.  These data were then layered with crop residue resource data to generate a map of the spatial distribution and amounts of crop residue amenable to bale collection and storage.