The economics of biomass harvesting are
addressed in several publications on this CD.
These date from 1987 through 2003.
Watson
and others (1992) compare
the costs of transportation, harvest operations, and woodyard handling and
chipping between two operational systems (long wood operations and in-woods
chipping operations). This was a
cooperative study with Mississippi State University, Rust International
Corporation,
The amount of fuel (energy) consumed to
produce energy wood was analyzed in cooperation with
Watson
and others 1987b offer a
discussion on the economics of obtaining biomass from logging residues (one-
and two-pass harvesting methods) and short rotation biomass plantations. This cooperative study with
Two studies (documented in Miller
and others 1985, Miller
and others 1987, and Watson
and others 1986b) calculated the
cost of producing energywood (in dollars per green ton) for each piece of
equipment used in the one- and two-pass methods. In the two-pass method, feller-buncher
productivity was significantly impacted by the amount of energywood
present. In the one-pass method, machine
productivity was not significantly different over the range of tonnages of available
biomass. The authors report that
intensive site preparation leads to lower energywood tonnages. This creates a production advantage for the
one-pass method as compared to the two-pass method.
In a cooperative study with Mississippi
State University, the University of California, and the Bureau of Indian
Affairs, Watson
and others (1995) investigated the
impacts of slope on the production of three different feller-bunchers (a
self-leveling excavator type track machine, a tri-track wheel machine, and an
intermediate sized track machine) used in a chipping operation. The thinning operation included merchandising
sawtimber and pulp quality chips.
Production on the wheeled machine was sensitive to slope, while the
other feller-bunchers were sensitive stem size.
Productivity rates for the flail/chipper, felling operation, and
skidding operation are displayed in regression equations.
Two reports (Stokes
1998 and Stokes
and Klepac 1998b) examine the
recovery and utilization of chips from three harvesting operations: a tree-length (long wood) operation, a flail
delimber/debarker and chipper operation, and a cut-to-length operation. Chip recovery and equipment production and
cost were analyzed for each type of operation on three loblolly pine (Pinus taeda) stands ranging from 13- to
23-years old. Harvest costs are affected
by tree size and utilization. The
tree-length operation was the least sensitive to tree diameters, while the
cut-to-length operation was the most sensitive.
(Gallagher
and Shaffer (2002) and Gallagher
and Shaffer (2003) provide an
introduction to the advantages and disadvantages of green plantation storage
versus traditional woodyard storage of hardwood in the South. While this study was tied to pulp production,
the same ideas and concepts could be applied to managing biomass inventory. The authors explore the costs and benefits
associated with using intensively managed short-rotation hardwood stands to
balance the pulpwood supply during wet winter months. Typically, mills increase their inventory in
preparation of the wet months. This
inventory has additional costs of storage, watering, deterioration, and
handling. Future related studies will
explore growth and yield models and silvicultural costs (land, irrigation, site
preparation, planting, annual maintenance, supervision, and harvesting) and
economic feasibility of intensively managed short-rotation hardwood stands as
compared to woodyard storage.
Site Preparation Costs
Harvesting understory material for biomass
can rarely be accomplished profitably.
In a study (Stokes
and Watson 1986c and
Watson
and others 1984) in south Alabama,
the Forest Operations Research Unit worked cooperatively with Mississippi State
University to question whether conventional systems could be used to harvest biomass,
and whether biomass removal reduced the site preparation costs enough to make
energywood harvesting economically feasible.
This study compared the site preparation costs following three harvest
methods (conventional, one-pass, and two-pass).
(These methods are explained in more detail under Biomass Harvesting Systems.) The conventionally harvested areas were
treated by (1) a shear, rake, pile and disk treatment or (2) by a herbicide
only treatment. Less mechanical
treatment was necessary for site preparation on the 1-pass and 2-pass treated
areas. Three site preparation treatments
(single disk, double disk, or herbicide) were applied on these areas. The one- and two-pass harvesting methods
removed more biomass, which translated to lower site preparation costs. The single disking application was the least
costly treatment. The study area was
visually inspected nine months after the site preparation treatments. The conventionally site prepared area had
similar vegetation regrowth as the double-disk treatment areas. These site preparation cost savings can be
considered a benefit to help offset the cost of biomass harvesting.
Both the one-pass and
two-pass harvesting methods resulted in reduced site preparation costs (Watson
and Stokes 1989). On the south Alabama study sites, only
discing was necessary to re-establish the stands after energywood
harvesting. Conversely, the site
preparation treatment of shear-rake-pile-disc following conventional harvesting
cost approximately $140/hectare more than energywood harvested sites.
Three different harvesting systems were used
in a study in northeast Mississippi (Ragan
and others 1987) which compared
the costs of conventional pulpwood harvesting, conventional pulpwood harvesting
plus in-woods chipping of biomass, and an intensive treatment consisting of
in-woods chipping for pulp quality chips and in-woods chipping of the biomass. The results of this cooperative study with
Mississippi State University and the Tennessee Pulp and Paper Company indicated
that energywood harvesting is marginally feasible, but when site preparation
costs are reduced due to the energywood harvest, these savings help offset the
cost of energywood harvesting.