INTRODUCTION
There has been an ongoing interest for hardwood sawmills to purchase hardwood sawlogs on a weight basis. Weight scaling is used frequently among hardwood scragg mills that purchase logs, generally smaller diameter and lower quality logs, to produce industrial products such as pallet parts. In that case, grade lumber for appearance graded markets is not an objective of the scragg mill and it is not critical to differentiate between species, except to state in their log specifications that certain species will not be accepted.
For purposes of weight scaling grade hardwood sawlogs, there are issues that arise. First, weight per unit volume is not consistent over the range of species. For example, and for simplicity’s sake, assume one thousand board feet (mbf) of 14-inch yellow-poplar logs, all 10-feet in length. Then, assume one mbf of 14-inch red oak logs, all 10-feet in length. Given that yellow-poplar weighs less per unit volume than red oak, the one mbf of yellow-poplar will weigh less that the batch of red oak logs. So, if we are interested in one ton of 14-inch, 10-feet long yellow-poplar logs and one ton of red oak 14-inch, 10 foot long logs, there will be more logs in the yellow-poplar batch than in the red oak batch.
Second, the one ton batch of yellow-poplar logs will yield more footage of boards than the one ton of red oak logs, simply because the weight difference between the two species results in more logs per ton in yellow-poplar than in red oak. In fact, one would expect a range of outcomes in board feet produced per ton of hardwood logs across the range of commercial species.
Third, it is also reasonable to expect some differences in board feet per ton, by species, over the range of diameters that a hardwood sawmill receives. Specifically, smaller diameter logs will generally produce fewer board feet per ton of logs, since the impact of removing the four slabs of a log is more impactful in smaller logs than larger logs.
The WVU Appalachian Hardwood Center (AHC) has, over the last decade plus, conducted over sixty sawmill studies throughout the Appalachian Region. These studies collected data on individual logs, where each log was measured and characterized according to a number of variables, including scaling diameter, length, scaling defects, as well as a number of other variables and then numbered on each end. The logs were then processed through the sawmill. Each board was graded and scaled, and the dimensions of each cant recorded, with all data being recorded by log number. The database contains over 4,600 logs of data and in many cases, the weight of each log was also determined.
ANALYSIS
For the purposes of this article, the analysis will focus on two species, yellow-poplar and red/black oak, as representing the two extremes of weight per unit volume and traditional popularity in the marketplace. They also represent the most common species represented in the AHC database, in addition to white oak/chestnut oak. For each log the sawn footage (bf) and log weight is known, by scaling diameter. The analysis then is simply to sum, for each scaling diameter (8-inches to 20+ inches) the sawn footage and the weight, then divide footage (in board feet) by the weight in tons.
Yellow-poplar
In the case of yellow-poplar the database contained 649 logs. Table 1 provides the results in board feet per ton by scaling diameter.
As mentioned earlier, the impact of removing the four slabs on a log is greater in smaller diameter logs, as the slabs constitute a higher proportion of the log weight, resulting in fewer boards (and footage) being produced, as shown for the 8/9 inch, 10 inch, and 11 inch logs. Starting at 12 inches the board feet per ton begins to stabilize with some fluctuations around the average of 240.9 board feet per ton, versus 236.6 board feet over all diameters.
Red/Black Oak
The red oak/black oak portion of the database contains 1,454 logs and Table 2 below summarizes the results for those logs.
One additional note here is that the red oak/black logs in the database are strongly weighted to the production of pallet sized cants, with railroad ties/timbers representing a smaller proportion of the cant products. As the proportion of tie/timber volume increases, the board feet per ton would increase as well. As such, these results are somewhat conservative with respect to footage per ton.
DISCUSSION
The analysis here is one piece of the puzzle in determining delivered pricing of weight scaled logs…expected yield of sawn lumber from one ton of logs of varying diameters. The second piece is the breakeven pricing (or pricing with profit included) for logs of varying scaling diameters and quality (i.e., clear faces). The third piece is how to price a load of logs with a variety of species.
The second piece can be developed from the database of individual logs at the AHC. Pricing algorithms are currently available to estimate delivered pricing, on a per ton basis, over a range of diameters and clear faces. This requires three pieces of information: lumber grade yields (from AHC database), lumber and cant pricing from one of the third party market reports or mill specific pricing, and sawing cost (mill provided). As an illustration, consider 13-inch red oak logs with 0, 2, and 4 clear faces with a yield of 181.5 board feet per ton (from Table 2), a sawing cost of $300 per mbf, breakeven pricing, and recent third party pricing (FAS = $ 1,035/mbf; One-Face = $1,025/mbf; Selects = $1,015; 1 Common = $689/mbf; 2A Common = $525/mbf; 3A Common = $480/mbf; 2B & 3B = $240/mbf; Below grade = $150/mbf; and pallet cants = $470/mbf). Note, the analysis does not include any tie or timber pricing, just pallet cant pricing. If a portion of the footage per ton were in railroad ties, for instance, the breakeven pricing would be higher.
These results show dramatically different breakeven prices for the 13-inch red oak logs for the three log quality levels: 0 CF = $28.03 per ton; 2 CF = $48.30 per ton: and 4CF = $72.81 per ton. The differences are due primarily to the increasing yield of higher grade lumber when moving from low grade to higher grade logs. Herein lies the problem for the third piece of the puzzle, establishing pricing by weight for logs of varying quality and to a lesser extent size. This problem is further exasperated with purchasing truckloads of multiple species, as evidenced in the difference in footage per ton of yellow-poplar versus red oak.
The major consideration in weight scaling should be what product mix is desired by the mill. If it is a grade lumber mill, with a focus on higher grades of logs, then it is probably not wise to pay by weight, as that relinquishes the mill’s ability to achieve the best outcome from graded and scaled logs. That is, the challenge is to accurately predict the quality of logs in a truckload being purchased solely on weight and assign a price that works for both the supplier and the receiving mill.
The better option for weight scaling hardwood sawlogs is in producing industrial products such as railroad ties, switch ties, pallet cants, pallet lumber, flooring lumber, and other uses for lower grade boards. That would mean purchasing low grade logs, with a focus on 1 and 0 clear faces. As mentioned earlier, this approach has been implemented successfully by scragg mills purchasing smaller diameter and lower grade logs.
