GROWTH AND UTILIZATION 



173 



volume. ^^ Loss of wood substance due to decay 

 in storage is estimated to vary from 2.5 to 3 

 percent in the South and West to 6 percent in the 

 North. Rejects of fines in screening chips may 

 range from 1 to 5 percent, depending on the 

 pulping process. Wood substance lost in barking 

 is estimated to range from 1 to 2 percent, depend- 

 ing on the method of barking and the use made of 

 the pulp. 



Log diameter and mill size are the principal 

 variables affecting residues in lumber manu- 

 facture. Comparatively more residues result in 

 sawing small logs than large, whether in large or 

 small mills, simply because a larger share of the 

 log volume is represented in slabs, edgings and 

 sawdust. Large mills, liowever, are generally 

 equipped for more efficient sawing and machine 

 operation than small mills are. Small mills and 

 small timber most often go together. Both are 

 characteristic of the North and South. Large 

 mills, on the other hand, are more characteristic 

 of the West, where large timber is still found in 

 abundance. 



In addition to log size, log quality and type of 

 product affect the amount of residue in veneer 

 manufacture. Good veneer timber has become 

 scarce in all sections of the country. As a conse- 

 quence, trees that would be regarded at the lower 

 margin for saw logs are used to an increasing 

 extent for lower grade plywood and containers. 

 Under these conditions, more of the log winds up 

 as residues despite efforts to save as much as 

 possible in the form of usable veneer by patching 

 and using the poorest material for cores or backing 

 in plywood, or for containers. 



Residues in relation to log input for lumber and 

 veneer are highest in the South (table 108). 

 With respect to lumber tliis may be attributed in 

 part to the preponderance of small softwood logs 

 in the cut, and in part to the poor sawing practices 

 prevalent at many of the thousands of small mills 

 which predominate in the area. In the West, of 

 course, residues represent a smaller share of the 

 log volume because larger timber is being cut. 

 The difference between the North and South is 

 perhaps due to the fact that the hardwoods that 

 make up the bulk of the cut in the Nortli average 

 somewhat larger than the general run of softwoods 

 cut in the South. 



Residue percentages in veneer manufacture are 

 higher in the South than in the West, largely 

 because southern veneer plants subsist on much 

 smaller and poorer quality logs than do western 

 plants. Residues from veneer manufacture in 

 the South are also somewhat higher than in the 



'' Aside from these residues, it is estimated that an 

 additional 40 percent of the wood used by all processes of 

 pulping in 1952 was dissolved in the various pulping 

 liquors or the water used for washing and conveying the 

 pulp. About 80 percent of the dissolved material was 

 recovered and used as fuel or for a variety of byproducts. 



North. This difference appears to be significant 

 but is difficult to rationalize. The higher per- 

 centage in the South may reflect the greater use 

 of relatively poor quality logs for container 

 veneer, a product which makes up more of the 

 veneer output in the South than in the North. 

 These logs generally yield a greater percentage 

 of residues than do the better quality logs used 

 for commercial and utility grades and face 

 veneers. 



Residue percentages are substantially higher 

 in pulp and cooperage manufacture in the North 

 than elsewhere. For pulp, this reflects the longer 

 storage period and consequent greater storage 

 losses, and for cooperage it denotes poorer average 

 quality of the material cut. 



Use of Plant Residues 



In 1952, about three-fifths of the total volume 

 of plant residues was used (fig. 69). About one- 

 half of the used residues were coarse and one-half 

 fine. Residues have long been burned for domes- 

 tic and industrial fuel. In 1952, fuel took 1.7 

 billion cubic feet, or 86 percent of all the residues 

 used (table 109). Put another way, the amount 

 used for fuel is the equivalent of about 31.5 

 million cords, or more than half of the total fuel- 

 wood output from all sources. Probably as much 

 as 60 percent of the coarse residues burned for 

 fuel are used for domestic purposes whereas most 

 of the fines are burned at industrial plants. 

 Rural areas, such as are common in much of the 

 South, Midwest, and Southwest, account for a 

 high percentage of the domestic wood used in the 

 form of slabs and similar coarse residues. On 

 the other hand, industrial use is generally asso- 

 ciated with large sawmills and veneer plants 

 where large quantities are directly available. 

 These residues frequently present a severe dis- 

 posal problem, and often provide the most 

 economical fuel where steam and heating require- 

 ments are large. This is the situation at many 

 of the large plants in the West. 



Although plant residues are used mostly for 

 fuel, they have not gone entirely unnoticed for 

 other purposes. About 5 percent of the total 

 used volume, for example, was for pulp and 9 per- 

 cent for a variety of other uses including agii- 

 culture (table 109). Other than fuel and pulp, 

 coarse residues were made into cut-up stock, 

 handles, brush blocks, chemical wood, boxboard, 

 lath, fence pickets, particle boards, and many 

 other commodities. Fines, though going mainly 

 into fuel, were also used in various other ways. 

 Some veneer clippings were pulped. Considerably 

 more fines went into mulches and soil conditioners, 

 bedding for livestock, poultry litter, insulation, 

 wood fioiu", linoleum filler, metallurgical use, and 

 a wide assortment of other applications. 



J. 



