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Solid wood and residue yield analysis of small-diameter red oak logs.

Abstract

A yield analysis of solid wood and residues from 233 red oak small-diameter logs (6 to 10 inches small end d.i.b.) was conducted. The results indicated that 75 percent of the 1-inch lumber was grade 2 A and 3 A, while the remainder was No. 1 common. The container part yield from the cants ranged from 63 to 66 percent. The total solid wood and residue weight yield included lumber and container parts (35%) chips (29%), sawdust (26%), and bark (10%). This research adds the yield of lumber, cants, residues, and container parts from red oak in the 6- and 7-inch diameter ranges to existing yield data. The lack of upper grade lumber yield in the small-diameter timber (SDT) in this study suggests a log purchasing strategy for lumber manufacturers capable of using SDT and wanting to avoid producing upper grades of red oak lumber. Lumber and pallet part manufacturers could use the yield information in this study to estimate their capability to utilize SDT.

In the eastern hardwood forest, where small, nonindustrial, private forests (NIPF) are the principal forest ownership group, diameter limit cutting is often the predominate method for harvesting timber (Fajvan 2006). One motivation for NIPF owners to harvest timber is to generate revenue from their property. The largest and thus highest-value timber is harvested, and the smaller, lower-value timber resides in the stand. This practice, known as high grading, has occurred for decades in the hardwood forest and has resulted in more residual low-value, low-quality smaller timber (Nyland 1992). In the southern industrial forest, there has been a decrease in the pulping capacity from 139,880 tons per day in 1994 to 127,390 tons per day in 2003, along with a simultaneous decrease in the production of pulpwood from 180.8 million green tons in 1994 to 162 million green tons in 2003 (Johnson and Steppleton 2003). Viable markets are needed to address these trends of decreasing demand for and increasing supply of smaller, lower quality timber.

Research to identify lumber yield from small-diameter hardwood timber (SDT) (Hanks et al. 1980, Cumbo et al. 2004) discovered high proportions of lower grade lumber, and these grades are often used in pallet and flooring manufacturing. Craft and Emanuel (1981) and Serrano and Cassens (2000) investigated the yield of pallet cants and pallet parts from SDT. Cants, container parts, and lumber were produced to investigate the yield of lumber and container parts from SDT. Red oak was chosen for the yield study because of its relative abundance in Southwest Virginia, and the lack of engineered wood product markets for ring-porous species. In addition, red oak is a common species for the flooring and pallet market, which Cumbo et al. (2004) suggested as a likely market for lumber derived from SDT.

Utilization of SDT by lumber manufacturers may become more important as companies seek to reduce costs, avoid producing higher grades of red oak, and as log supplies become more limited to smaller and lower-quality logs. The objective of this research was to determine the volume yield of lumber, cants, container parts and residues from red oak SDT. This yield data were subsequently used in another study in order to address the economic viability of utilizing red oak SDT.

Methods

A yield study was initiated at a local hardwood scragg mill that is operated in unison with a pallet and container part manufacturing operation. This particular scragg mill had a shifting twin circular saw and rotating end dogging set-up, gang resaw, edger, and trimmer. The pallet and container part operation consisted of a cut-off-saw, gang resaw, part salvager, and a double-head notcher. The scragg mill was chosen because its design allows processing of logs into cants and lumber at high feed rates, and has low investment and operating costs (McCay and Wisdom 1984).

After discussions with mill personnel at the case-study mill, the minimum acceptable inside bark diameter was set at 6 inches due to limitations of the log processing equipment. Given this restriction, the small-end diameter range was limited to between 6 and 10 inches.

The red oak logs used in the study were sampled from the participating mill's log inventory. The target sample size was 50 red oak logs for each 1-inch small-end diameter class from 6 to 10 inches, for a total of 250 logs. The small-end diameter was measured along two axes (perpendicular to each other) and averaged, and the length of the logs was also measured. The range for each diameter group was from 0.4 below the nominal diameter to 0.5 above the nominal diameter. For example, the diameter range for the 6-inch group was from 5.6 to 6.5 inches. Each group of logs was marked with a unique color on the end of each log in order to facilitate sorting and tracking. All logs were below USDA Forest Service grade three logs due to diameter limitations of the USDA Forest Services' Standard Grades .for Hardwood Factory Lumber Logs (Vaughan et al. 1966, Rast et al. 1979), and further analysis of log quality was not included in the study. The participating scragg mill produces lumber from relatively lower quality, smaller logs as compared to a grade sawmill. The logs in the 6- and 7-inch diameter groups were sampled from a log pile that had been sorted for species from their pulpwood inventory. A summary of the logs used in the yield study is summarized in Table 1.

There were only 33 logs in the 6-inch diameter group due to log availability and time considerations. The participating mill sorted the logs into the respective diameter groups, emptied chip bins, removed bark from around the debarker, and supplied a dump truck to facilitate the weighing of chips and sawdust. Each group of logs was milled separately but sequentially through the sawmill.

First, the logs were debarked by a Rosser-head type debarker. The logs were sawn at the scragg headrig that produced a two-sided cant, slabs and sawdust. The slabs were chipped. The weight of chips and sawdust produced from each log group was determined by scales on site. It was not possible to weigh the bark, so the bark pile's cubic volume was measured and then converted to a weight. The total bark weight was estimated by multiplying the volume by green bulk density (25.8 pcf) of hardwood sawdust and bark (Harris and Phillips 1989).

The weight of bark for each log group was calculated using weighted ratios. The weight of bark was allocated to each log group as a ratio of each log group's volume to total log volume. For example, the log volume for each log group was calculated by summing the volume of individual logs in that group. The total log volume of all five log groups was calculated by summing the volumes for all groups. The ratio was calculated as shown in Equation [1].

[Ratio.sub.i] = [V.sub.i]/[V.sub.T] [1]

where:

[V.sub.i] - volume for [i.sup.th] group

i = the [i.sup.th] diameter group and

[V.sub.T] - total log volume of all groups.

This ratio was calculated for each log group. Each group's ratio was then multiplied by the total weight of bark to determine the weight of bark for each log group as shown in Equation [2].

[W.sub.i] = [Ratio.sub.i] * [W.sub.T] [2]

where:

[W.sub.i] = bark weight for the [i.sup.th] group

[Ratio.sub.i] = ratio for the [i.sup.th] group

i = the [i.sup.th] diameter group and

[W.sub.T] = total bark weight.

After initial breakdown at the scragg headrig (0.3125-inch sawkerf), the two-sided cants were processed through a gang resaw (0.16-inch sawkerf), which produced a 3-inch thick cant and 1 -inch thick lumber. The cant volume was measured, and it was sent to the pallet and container part operation where it was cut to length (70-inch, 51-inch, and 46-inch) and processed into container parts through a gang resaw (0.16-inch sawkerf). The container parts were manufactured for a wood container manufacturer who specified the size of the part to be 7/16-inch thick and 3 inches wide. The lumber was edged, end trimmed, tallied, and graded according to the National Hardwood Lumber Association's grading rules. The container parts were measured and then counted. Cull container parts were counted but not included in the volume yield. This process was repeated for each log group. Overrun and under-run were calculated using cant and lumber volumes (international 1/4-inch scale). Lumber and container part yield were calculated with nominal thickness, l-inch and 7/16-inch, respectively.

Results

The lumber, container part and residue weight yield for all log groups was 35 percent solid wood, 29 percent chips, 26 percent sawdust, and 10 percent bark as shown in Figure 1. Lumber and container parts totaled 14.0 tons, chips 11.7 tons, sawdust 10.3 tons, and bark 4.2 tons. Because the weight of lumber and container parts was not measured, it was estimated by multiplying the measured footage at the average green MC (75%) by the weight per MBF (5,102 lbs) from the Dry Kiln Operator's Manual (Simpson 1991).

The amount of total residue per BF of lumber produced was inversely proportional to log diameter. The residue yield range of 5.4 tons/MBF for the 6-inch group to 4.4 tons/MBF for the 10-inch group, which is similar to those reported by Page and Baxter (1974) and Massengale (1971). The overall residue yield (excluding solid wood) of 45 percent chips, 39 percent sawdust, and 16 percent bark was comparable to yields discovered in other studies (Page and Baxter 1974, Massengale 1971).

The proportional volume of cants decreased as log diameter increased. In the six-and 7-inch log groups, cants accounted for more than 70 percent of total log group volume; whereas in the 10-inch group cants account for only 54 percent of total log group volume. The yield of cants and lumber is shown in Figure 2. The decrease in cant volume, from 72 percent in the 6-inch group to 54 percent in the 10-inch group, as diameter increased is evident in other yield studies (Craft and Emanuel 1981, Holt 1993). The cant thickness remained the same, 3 inches in this study, but the cant width increased, and the amount of 1-inch-thick lumber increased as the diameter increased.

The 1-inch-thick lumber that was produced was low grade, with 2A and 3A accounting for 55 percent and 19 percent, respectively. Number one common lumber accounted for 24 percent of the total lumber produced with the 8-inch and larger groups having more than one-quarter of their total lumber volume yield 1C lumber.

Container part yield ranged from 63 to 66 percent and there was no obvious relation to log diameter. This yield is less than cant grade two, 77 percent yield, but greater than cant grade three, 47 percent yield, according to the grading scheme suggested by Mitchell et al. (2005). The authors proposed three cant grades based on the percent of sound wood. A grade one cant had zero to 15 percent unsound wood and yielded 83 percent pallet parts. Grade two cants had 16 percent to 30 percent unsound wood and a 77 percent pallet part yield, and grade three cants had over 30 percent unsound wood and a 47 percent pallet part yield. The part yield achieved in this study was in accordance with the weight yield, 64 percent, found by Serrano and Cassens (2000). These results, when compared with the previous research, suggest that these part yields should be attainable by pallet-part mills on a continuous basis. Depending on the log group, between 60 percent and 75 percent of the container parts were 70 inches long.

The overrun and underrun was based on the cant and lumber volume for each log group in the yield study. The overrun for the 6-, 7-, 8-, and 9-inch log groups was 54 percent, 22 percent, 10 percent, and 1 percent, respectively. The 10-inch group had an underrun of 2 percent. The overrun can't be compared to other studies (Hanks et al. 1980, Holt 1993) because they lack these diameter groups. Both of these cited studies graded logs according to the USDA Forest Services' Standard Grades .for Hardwood Factory Lumber Logs (Vaughan et al. 1966, Rast et al. 1979). This multiple grade (F 1, F2, and F3) system excludes logs less than 8 inches scaling diameter. This exclusion limits the ability of researchers to compare the relative quality and yield of small-diameter logs.

Summary

The total solid wood yield included lumber and container parts that accounted for 35 percent. The total residue weight yield included chips (29%), sawdust (26%), and bark (10%). The majority of solid wood produced was in the form of 3-inch thick cants, whose proportional volume decreased with increasing log diameter. Seventy-four percent of the total lumber produced was 2A and 3A, and 24 percent was number one common. The yield of container parts ranged from 63 to 66 percent.

This research adds the yield of lumber, cants, residues, and container parts from red oak in the 6- and 7-inch diameter ranges to existing yield data. The lack of upper-grade lumber yield in the SDT in this study suggests a log purchasing strategy for lumber manufacturers capable of using SDT and wanting to avoid producing upper grades of red oak lumber. Lumber and pallet-part manufacturers could use the yield information in this study to estimate their capability to utilize SDT.

Literature Cited

Craft, E.P. and D.M. Emanuel. 1981. Yield of pallet cants and lumber from hardwood poletimber thinnings. Res. Pap. NE-482. USDA., Forest Serv., Northeast Forest Expt. Sta., Broomall, Pennsylvania. 6 pp.

Cumbo, D.W., R.L. Smith, and C.W. Becker. 2004. Value analysis of lumber produced from small-diameter timber. Forest Prod. J. 54(10): 29-34.

Fajvan, M.A. 2006. Res. on diameter-limit cutting in central Appalachian forests. In: Proc. of the Conf. on Diameter-Limit Cutting in Northeastern Forests, L.S. Kenefic and R.D. Nyland, eds. May 23-24, 2005, Amherst, Massachusetts. Gen. Tech. Rept. NE-341, U.S. Forest Serv.:32-38. Northeastern Res. Sta., Newtown Square, Pennsylvania.

Hanks, L.F., G.L. Gammon, R.L. Brisbin, and E.D. Rast. 1980. Hardwood log grades and lumber grade yields for factory lumber logs. Res. Pap. NE-468. USDA Forest Serv., Northeast Forest Expt. Sta., Broomall, Pennsylvania. 92 pp.

Harris, R.A. and D.R. Phillips. 1989. Bulk density of seven typical industrial wood fuels. Forest Prod. J. 39(1):31-32.

Holt, D.H. Pennsylvania red oak log yields. 1993. Bureau of Forestry, Commonwealth of Pennsylvania. In: Denig, J., Small Sawmill Handbook: Doing it Right and Making Money, Miller Freeman, San Francisco, California. 182 pp.

Johnson, T.G. and C.D. Steppleton. 2003. Southern pulpwood production, 2003. Resource Bulletin SRS-101. USDA Forest Serv., Southern Res. Sta., Asheville, North Carolina. 38 pp.

Massengale, R. 1971. Sawdust, slab and edging weights from mixed oak logs from the Missouri ozarks. The Northern Logger and Timber Processor 19(10):28-29. In: Koch, P., 1985, Utilization of Hardwoods Growing on Southern Pine Sites. USDA Forest Serv., Agriculture Handbook No. 605. U.S. Government Printing Office, Washington, D.C. 3,710 pp.

McCay, T.D. and H.W. Wisdom. 1984. Feasibility of small mill investments for utilizing small-diameter hardwood from coal lands in southwestern Virginia. Forest Prod. J. 34(6):43-48.

Mitchell, H.L., M. White, P. Araman, and P. Hamner. 2005. Hardwood pallet cant quality and pallet part yields. Forest Prod. J. 55(12):233-238.

Nyland, R.D. 1992. Exploitation and greed in eastern hardwood forests. J. of Forestry 90:33-37.

Page, R.H. and H.O. Baxter. 1974. A new look at residues from Georgia's primary wood manufacturing industries. In: Koch, P., 1985, Utilization of Hardwoods Growing on Southern Pine Sites. Ga. For. Res. Pap. 78, Ga. For. Res. Counc., Macon, Georgia. 11 pp. USDA Forest Sew., Agriculture Handbook No. 605, U.S. Government Printing Office, Washington, D.C. 3,710 pp.

Rast, E.D., D.L. Sonderman, and G.L. Gammon. 1979. A Guide to Hardwood Log Grading (revised). USDA Forest Serv. GTR NE-1.32 pp.

Serrano, J.R. and D. Cassens. 2000. Pallet and component parts from small-diameter red oak bolts. Forest Prod. J. 50(3):67-73.

Simpson, W.T. (ed.). 1991. Dry Kiln Operator's Manual. USDA Forest Serv., Forest Products Lab., Madison, Wisconsin. 274 pp.

Vaughan, C.L., A.C. Wollin, K.A. McDonald, and E.H. Bulgrin. 1966. Hardwood Log Grades for Standard Lumber. Gen. Tech. Rept. FPL-63. USDA Forest Serv., Forest Products Lab., Madison, Wisconsin. 53 pp.

Brian Perkins * Robert L. Smith * Brian Bond *

The authors are, respectively, Graduate Research Assistant, Dept. of Wood Sci. and Forest Products, Associate Dean for Extension, College &Natural Resources, and Associate Professor and Extension Specialist, Dept. of Wood Sci. and Forest Products, Virginia Tech, Blacksburg, Virginia (perkinsb@vt.edu, rsmith4@vt.edu, bbond@vt.edu). The authors would like to acknowledge the Virginia Dept. of Forestry for their contribution to the project and the Center for Forest Products Marketing and Management for support. This paper was received for publication in May 2007. Article No. 10351.

* Forest Products Society Member. [c] Forest Products Society 2008. Forest Prod. J. 58(1/2):97-100.
Table 1.--Log sampling summary.

 (inches)
 Total or
Log group 6 7 8 9 10 average

Number of logs 33 50 50 50 50 233
Average diameter (in) 6.2 7.2 8.1 9.0 9.9 8.1
Average length (ft) 12.5 11.6 11.2 11.3 11.4 11.6
Log scale (int. 1/4) 496 995 1272 1653 2103 6518
Volume ([ft.sup.4]) 87 164 200 248 304 1002

Figure 1.--Total solid wood and residue yield.

Chips 29%
Saw Dust 26%
Bark 10%
Solid Wood 35%

Note: Table made from pie chart.

Figure 2.--Cant and lumber yield.

 Cants 3A 2A 1C 1F FAS
6" 72% 6% 21% 1%
7" 72% 6% 18% 3%
8" 64% 9% 17% 10%
9" 61% 6% 21% 11% 1%
10" 54% 7% 23% 13% 1% 2%

Note: Table made from bar graph.
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Title Annotation:Technical Note
Author:Perkins, Brian; Smith, Robert L.; Bond, Brian
Publication:Forest Products Journal
Geographic Code:1USA
Date:Jan 1, 2008
Words:3032
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