Page 396 - Solid Waste Analysis and Minimization a Systems Approach

374 WOOD- AND LUMBER-MANUFACTURING APPLICATIONS

A recent study by the U.S. Forest Service, State & Private Forestry (S&PF), demon-
strated the potential of thin kerf sawing when used in combination with other lumber-
recovery practices. Twenty red oak logs with lengths of 4 to 6 ft and diameters
between 12 and 20 in were sawn with a saw kerf band saw (0.062 in saw kerf). Boards
sawn were 1-in thick and ranged in lengths from 2 to 6 ft. Lumber recovery or con-
version efficiency for the 20-log sample averaged 82 percent, which is 30 percent
greater than the typical circular sawmill.
A similar study of small-diameter (4–8 in) red and white pine logs was conducted
by S&PF. Using the same thin kerf band saw as noted above the lumber recovery for
the 47-log sample was 67 percent. Sawdust averaged 12 percent for the study.
A third study conducted at a Missouri pallet mill in 1993 produced results very sim-
ilar to the pine study. The Missouri mill reduced short hardwood logs (length of
45 in) to 5/8-in-thick pallet parts. The band saws utilized in the pallet operation had
saw kerfs of 0.050 in. The average conversion efficiency at this mill was calculated at
69 percent which is remarkable considering 5/8-in-thick lumber, rather than 1-in lum-
ber, was produced. Thin lumber such as 5/8 in means more cuts and, consequently,
more kerf removed, resulting in reduced conversion efficiency. However, 69 percent is
still very impressive.
As well as the obvious benefits described above, on a more local level, thin kerf saw-
ing will enable the use of lower quality and/or smaller diameter logs, which otherwise
may have little or no economic value. Consequently forest management could be stim-
ulated to improve and expand the resource base and lead to more successful rural devel-
opment efforts in retaining, expanding, and attracting wood-using industries.
In increasing lumber recovery and simultaneously reducing waste, thin kerf sawing
has the added potential benefit of keeping some sawmills profitable and in-business.
In effect, the adoption of thin kerf technologies can save jobs by enabling mills to con-
tinue to operate.
Following is a list of diversion options for their wood waste in preferred order of
implementation:

1 Source reduction—Source reduction, including reuse, can help reduce waste dis-
posal and handling costs, because it avoids the costs of recycling, municipal com-
posting, landfilling, and combustion. Source reduction also conserves resources and
reduces pollution, including greenhouse gases that contribute to global warming.
2 In-process and off-site recycling—Wood shavings and sawdust may be reused
internally or as a raw material for other operations. Sawdust is a primary material
in particleboard.
3 Energy recovery—Energy recovery includes any technique or method of minimiz-
ing the input of energy to an overall system by the exchange of energy from one
subsystem of the overall system with another. For example, wood scrap may be
burned to heat a building or water tanks. Biofuels potential is another option.
Energy production from unused wood fiber has been identified as a potential oppor-
tunity for the forest industry. Higher energy costs may make this opportunity eco-
nomically viable.