~outnern I"U Ip and I"aper Manufacturer 40(5): 17, 18', 20, 22.May 1977. -:~;2

Taproots Is EconomicPines With

Acre 20 PercentTo Boost

By Peter KochChief Wood Scientist

Southern Forest Experiment Station

ground level and is 1.5. to 2 timesstem diameter at breast hei~t.

In structure, rootwood varies con-siderably from stemwood. Roots makevirtually uninterrupted growththroughout all 12 months of the year.Although distinct bands of latewoodare sometimes found, growth incre-ments are more often distinguished byseveral rows of radially flattened cells,whose walls may be no thicker,.thanthose of earlywood. Frequency, size,and distrubution of bordered pits inrootwood tracheid walls are morevariable than in stemwood" and fibrilangles may be larger. The pit structureis not likely to affect pulping processesgreatly, but large fibril angles maylead to inferior paper properties:Except for a gre;,ter incidence of raytracheids elongated perpendicularly tothe rays and the virtual absence of

At the Southern Forest ExperimentStation, we've been trying to extendthe pulpwood resource by bringingmore of each pine tree to the millyard. The taproot of a 15- to 3D-year-old southern pine weighs about 20%as much as the merchantable stem(Table I). Harvesting and pulping thiswasted material would greatly increasepulpwood tonnage yield per a.cre. Butis it feasible to do so?

To answer that question, we begana series of studies aimed at (1) deter-mining if the taproot is physically andchemically suited for kraft pulpingand (2) developing the needed har-vesting machinery.

Taproots Suitable for PulpPine taproots are carrot-shaped and

generally 3 to 5 feet long. Maximumdiameter occurs a few inches below

thick-walled parenchyma cells, root-wood rays and r~ canals resemblethose of stemwood.

In a sample of 20 southern pin~aged 12 to 89 years, Manwiller (1972)found that rQotwood tracheids wereone-third larger in diameter than stem~wood tracheids measured at stumpheight; rootwood cell walls were 18%thinner, and lumens were almost two-thirds larger (Table II). Observationson the taproot, of a single tree furtherrevealed that all cell dimensions in-creased to a maximum at a pointabout 1.5 feet below ground level andthen diminished.' In this tree, mini-mums of length (3.2 rom), diameter(44 JL m), and wall thickness (4 JL m)occur:red. about 10 inches below thepoint where the maxima were ob-served.

To pro'lide some data onchemi,alconstitutients, Howard (1973) up-rooted three 22-yxar-old slash pinesgrowing in central Louisiana on well-drained sandy loam soil in an un-thinned plantation. Lateral ~.oots weresevered at a radius of 3 feet. Root-wQ9d had slightly more extractiv~,lignin, and ash and slightly less cellu-lose than stemwood (Table III). Theroots had a moisture content of 111percent and specific gravity of 0.38{basis of unextracted, ovendry weightand green volume); stemwood aver-aged 116 percent in moisture contentand 0.47 in specific gravity. In short,it seems likely that taproots of thesouthern pines are pulpable by thekraft process, a conclusion supportedby the work of Sproull et al. (1957).Because of chemical composition,slightly lower yields than those ob-tainable from stemwood can beexpected. More recently Keays (1974)concluded that use of naturallyoccurring percentages of stumps androots of mature conifers would havelittle effect on strength of kraft pulps.

Moreover, roots are more suitablefor pulping than either branches ortops; i.e., roots have higher alphacellulose and lower lignin content thantops or branches (Table ill). To takeadvantage of this wasted resource, amachine was designed to first shearthe laterals close to the taproot andFig. l-Tree puller, showing typical functioning.

May 1977/50uthern Pulp and Paper Manufacturer 17

then pluck the entire tree from theground (Koch and Coughran 1975,Koch 1976).

Table H.-Mean tracheid dimensions in root and stumpwood of 20 southernpines.

Stumpwoodb RootwoodeStandard Standard

Dimension Mean deviation Mean deviationLength (mm) 3.0 0.64 4.0 0.89Cell diameter <1£ m) 38.8 9.39 52.5 12.21Lumen diameter <1£ m) 25.7 11.06 41.7 13.08Wall thickness (JI. m) 6.6 2.15 5.4 1.67

a Data from Manwiller (1972).b Stumpwood sampled from two opposed 2O-decree wedges (I-inch thick) removed18 to 24 inches abo~ lJ'ound JeveLc Sampled from disks taken along the taproot beginnina at the point where major lateralswere attached.

loads of stems are alternated so thaton one load the roots are forward andon the next to the rear; this procedurepermits building a maximum-weightload without exceeding height limita-tions.

. At the mill, full truckloads ofcomplete-free stems are fork-lifted in-to large cradles for subsequent massbucking (with bundle-bucking chain-saws) into 8-foot pulpwood lengths.

. The 8-foot pulpwood. as it isbucked, falls onto a chain conveyorleading to a drum debarker.

. All pieces are cleaned of dirt anddebarked in the drum debarker; bark(with considerable dirt content) is con-veyed to the powerplant throughcleaning equipment to reduce dirt con-tent to levels tolerable by the burningequipment.

. Bark-free (and remarkably dirt-free) wood emerges from the drum de-barker to pass through disk chippersand hence into the pulp mill.This procedure is summArized inFigure 4.

The harvesting cycle is completed

Tree PuDerThe machine, manufactured by

Rome Industries, Cedartown, Georgia,can be fitted through a quick-hitchmechanism on a number of primemovers-for example, a Caterpillar 920or a John Deere 544B (Fig. 1).1 Twoelements are eentral to the design.The first is a scissors-type gripachieved with a pair of stout hori-zontal knife blades that close atgroundline and bite several inches intothe stem from opposite sides.

With this grip anchor, the secondelement in the design oomes intoaction. It is a clamshell-hinged tubularshear, 22 inches in diameter and madeof 3/4-inch-thick steel. The shear,sharpened on the lower edge, is forcedvertically into the ground to a depthof 11 inches. thereby severing lateralroots all around the tree. At thispoint, broad steps on opposite sidesof the shear strike the ground -aDdprevent further penetration. An ad-ditional stroke of the hydraulic cylin-der raises the grips 9 inches while thesteps remain pressed against the soilsurface. The effect is to jack the stemand break it free of the ground.Finally, the complete tree is lifted intothe air and bunched for skidding.Since shearing takes only a few sec-onds, a tree can be harvested andbunched in about half a minute.

Harvesting and Utilization SystemTo a considerable extent, the utili-

zation system is controlled by dirt thatadheres to the taproot. Such adherenceis more severe in clay soils than insandy soils. Much of this dirt is shakenfree when trees are bunched, skidded,delimbed, and stacked (Fig. 2), buta significant amount remains. Thisresidual dirt and adhering bark shouldbe removed before chipping for pulp.

To this end, a harvesting systemfor pine plantations on sandy soils isproposed as follows:

. Trees are pulled entire andbunched.

. Bunched trees are thrust tops firstthrough a delimbing gate (Fig. 3) andskidded to roadside.

. At roadside, tops and taprootsare cut to 2- or 3-inch diameter insidebark with a chainsaw, and potentiallytroublesome stubs of lateral roots aretrimmed.

. Complete trees are grapple-loaded(Fig. 2) onto trucks with 20-ton pay-load for transport to the mill. Grapple-

1 Mention of trade names is solely for in-formation purposes and does not implyendorsement by the U.S. Department ofAariculture.

Fig. 2-Longleaf and slash pines with taproots attached, ready to load.

18 Southern Pulp and Paper Manufacturer/May 1977

landing2 truck driversSupervision (assumes super.

visor is handling 3 or 4logging sites)

Total labor

15,00030,(KX)

7,000$112,000

OperatiooaI ExpeD8eSAnnual operating expenses for oil.

fuel. maintenance. and parts shouldbe about as follows:

Maehine Annual cost(1,081 operatiDg boon)

Puller-buncher. $16 perhour $17,296

Two grapple skidders. $14per hour each 30.268

Roadside grapple loader.$12 per hour 12.972

Two tractor-trailer highwaytrucks (with 4 trailers).$24 per hour 25,944

Supper truck, $6 per hour 9.000Total $95.480

This total is 1.9 tinles annual deprecia-tion charge.

Total ADDuai Costs

utilization, or 0.563 hour out of everyscheduled hour.

The machines will be scheduled 5days per week, 8 hours per day, 48weeks per year (allowing 4 weeks forvacation and holidays). Thus, a total1.920 hours will be scheduled eachyear. Actual operating hours willtherefore total 0.563 x 1,920 hours.or 1,081 hours per year.

At two trees per operating minuteand 500 trees per acre, 0.24 acreshould be harvested per operatinghour. Acres harvested annually shouldtherefore total 259.

Labor CostSeven men are needed to operate

the harvesting and delivery system.Cost of manpower, including super-vision (but excluding mechanic's labor.which is covered under operationalexpense) should total about $112,000:

r:~#

Amount$50,580112,000

ItemDepreciationLabor and supervisionOn. fuel, maintenance,

and partsTotal

by replanting the well-prepared site.Holes left after harvesting vary frominconspicuous indentations to cavities22 inches wide and a foot deep. Skid-ding activity in combination with nor-mal rainfall partially fills most holes.

Cost of Wood Delivered to MiDThe harvesting system envisioned

(Fig. 4) is designed for clearcuttingunthinned stands perhaps 25 years oldthat average about 8 inches in dbh(12-inch maximum on any tree). It isassumed that each acre carries 500trees averaging 600 pounds in greenweight when shorn of limbs andlateral roots. Puller-buncher produc-tivity with an experienced operatorshould average two trees per operatingminute (Fig. 5).

Equipment Cost And DepreciationTotal investment in equipment

should be approximately as follows:

Machine CostPuller-buncher $60,0002 grapple skidders 86,000Portable delimbing grate 1,000Roadside grapple loader 31,0004 set-out log trailers 24,0002 diesel truck-tractors 64,000Support truck 15,000

Investment in system $281,000

Under 5-year straight-line deprecia-tion with 10% residual value, annualdepreciation is

$281,000 - 28,100 =$50,580.

years

The equipment in the system issintple, highly practical, and thorough-ly field-tested; therefore, all fourwoods machines in combination shouldbe mechanically functional (available)75 percent of the time. Of this avail-able time, they should be operating75 percent of the time. Net operatingtime is thus 0.75 availability x 0.75

Function Annual costincluding

fringe benefits4 machine operators at $60,000

$lS,OOO each (for puller-buncher, 2 skidders, andgrapple-loader)

1 chainsaw operator at the

Annual CatIt BenefitsBenefits from the system include

site preparation, here assumed to be$30 per acre, as well as receipts forwood:

Item AmonntSite preparation$30/acre x 259 acres/year $7,700Complete-tree stems delivered

tomill$6.4443/ton x 500 trees/acrex 0.3 green ton/treex 259 acres/year-$6.4443/green ton x 38,850

tons/year 250,360Total ~$258,060

From the foregoing computation, it isevident that harvesting costs of $6.44per green ton delivered result fromthis system.

Profit on CapitalIf 30% profit on investment (be-

fore income taxes) Is required, annualprofit must amount to 0.3 x $281,000,or $84,300. If this profit is allocatedover the 38,850 tons of green pulp-wood delivered to the mill each year,it amounts to $2.17 per green ton.Pulpwood price, delivered to mill yard(including woodlands profit on equip-

20 Southern Pulp and Paper Manufacturer/May 1977

95,480-$258,060

Fig. 3 - Grate-type delimber.Bunched trees are thrust tops firstthrough this apparotus, which snearslimbs from the stems.

~

~

~

Fig. 4-Harvesting and utilization system.

meat inv~tment) should therefore be$6.44 plus $2.17, or $8.61 per greenton. plus stumpage price.

CoDclllsloD

One can draw the following con-clusions about harvesting even-agedsouthern pine plantations with aboutSOO trees per acre averaging 8 inchesin dbh and weighing 600 pounds greenwhen stripped of lateral roots andbranches:

. Using a puner-buncher instead ofa feller-buncher should increase pulp-wood tonnage harv~ted per acle byabout 20 percent.

. Drom debarken can clean barkand dirt from pine taproots and stemssobarvested

. Bark-free rootwood mixed withstemwood in its niturally ~urringproportioQ$ should not adversely affectkraft pulp properties in any importantway.

. Harvesting equipment for a tree-pulling system will likely cost about$281,000; the equipment n~ded in-cludes a tree ptiller-buncher, twograpple skidden, two IOS trucks, fourset-out log trailers, and a supporttruck. With this system, about 259acres can be harvested annually dur-ing 48 forty-hour weeks.

. O>st of wood (including stembark) so barwsted and delivered tothe mill yard, including 30% pre-income-tax profit on equipment in-vestment, should be about $8.61 pergreen ton plus cost of stumpage. .

. IJ~ CItedHoward, E. T. 1973. Physical and

chemical properties of slash pine treeparts. Wood Sci. S(4):312-317.

Keays, J. L. 1974. Full-tree andcomplete-tree utilization for pulp andpaper. For. Prod. J. 24(11):13-16.

Koch, P. 1976. New technique forharvesting southern pines with taprootattached can extend pulpwood re-sources significantly. Appl. Polym.Symp. 28:403-420. John Wiley &;Sons, Inc.

Koch, P., and S. J. Coughran. 1975.Development of a puller-bunch« forharvesting southern pines with tap-root attached. For. Prod. J. 2S(4):23-30.

ManWl"Der, F. G. 1972. Tracbeiddimensions in rootwood of southernpine. Wood Scl. 5(2):122-124.

Moore, W. Eo, and D. B. Johnson.1967. Procedures for chemical analysisof wood and wood products. USDAFor. Serv., For. Prod. Lab., Madison,Wis.

Sproull, R. C., R. B. Parker, andW. L. Belvin. 1957. Whole tree har-vesting. For. Prod. J. 7(4):131-134.

fI)Q~70Q\J

~,~.o~~~O

~'q

40

~~50

..,~"'20' I I I I I I I I

4 ~ 67 8 910 111215TREE 0.8. H. (INCHES)

Fig. 5-Relationship between tree dbh and time to pull and bunch planta-tion-grown loblolly pines 15 yeors of age. (Data source: D. M. Tufts, Pine-ville Kraft).

22 Southern Pulp and Paper Manufactarer/May 1977