Short rotation woody crop operations differ from conventional forestry operations because the trees are specifically grown for fiber harvest on rotations of approximately 5 to 8 years. These stands are typically characterized by small diameter and high stems per acre. Several studies explored harvesting operations that could be used in short rotation woody crops. Handling multiple small stems and bunching to increase productivity are just two of the factors that make handling this small diameter material different from conventional-sized materials. Some of the publications on the CD refer to using short-rotation crop production for pulp furnish. It may be appropriate to apply these operational findings to the harvesting of biomass.
Sycamore (Platanus occidentalis), black locust (Robinia pseudoacacia), and Eucalyptus
spp. have been identified for short rotation crop species (Hartsough
and others 1992 and McDonald
and Stokes 1994b).
Over the years, an assortment of equipment has been built and tested for handling multiple small stems (Hartsough and Stokes 1997b). The Forest Operations Unit has analyzed a variety of harvesting systems to identify bottlenecks and find opportunities to improve productivity when harvesting small stems (Hartsough and others 1992, Stokes and Hartsough, 1993a, McDonald and Stokes 1994a, Hartsough and Cooper 1999b, and Hartsough and Cooper 1999c). Even non-traditional woodyard equipment, such as front-end loaders for forwarding, was investigated (Spinelli and Hartsough 2001). Many of these studies indicate that average d.b.h. is the most critical factor in predicting productivity of conventional felling systems in short rotation stands (McDonald and Stokes 1994b). System balancing is important when developing harvesting systems for small diameter stems.
An annotated bibliography (Stokes and others 1997) summarizes 354 publications that address the operational aspects of woody crops for energy. It was published in 1997 for the International Energy Agency Bioenergy multi-national collaborative agreement. Some of the publications cited within this document would be difficult to find, even with Internet search engines available today.
Management of short-rotation woody crops
differs from conventional management in many ways. Hartsough
and Yomogida (1996) provide a
detailed overview of short-rotation woody crop management, from planting, to
weed and pest control considerations, to harvesting and transport. This study was a cooperative effort with the
Another benefit of growing short-rotation woody crops could be to provide standing inventory during wet periods for pulp mills (Gallagher and Shaffer 2002 and Gallagher and Shaffer 2003). This possibly translates to standing inventory of biomass for energy plants, too. Gallagher and Shaffer (2003) relate mill inventory and standing inventory usage at three mills over a 3-year period.