640 



Yearboo\ of Agriculture 1949 



the old, provide a practical approach 

 to the chemical utilization of wood 

 residues. 



Wood residues are especially adapt- 

 ed for chemical processing because 

 wood of any form or size or quality 

 can be used. Sawdust, shavings, slabs, 

 trimming, cordwood, and cull logs are 

 all suitable. Further, the presence in 

 the residue of relatively large amounts 

 of knots, bark, and even wood in the 

 early stages of decay does not interfere 

 with most of the processes, although it 

 may reduce the yield of chemical prod- 

 ucts. Even though it would usually pay 

 to process the hardwoods (broadleaved 

 species) separately from the softwoods 

 (cone-bearing species) for the reason 

 that the products and yields from those 

 two general classes of wood differ, it 

 is not necessary generally to separate 

 them. 



The amounts of wood residues avail- 

 able indicate the possible magnitude of 

 a chemical industry based on their full 

 utilization. Naturally, the first wood 

 residues to be considered for such an 

 industry would be those that occur at 

 sawmills, veneer mills, and secondary 

 manufacturing plants, because the ma- 

 terial is already at hand and a large 

 part (in the form of sawdust and shav- 

 ings) is already reduced sufficiently in 

 size for use. Some 16 million tons of 

 such material now remain unused each 

 year. An additional 27 million tons are 

 burned to generate steam for plant 

 operations. As soon as its chemical- 

 processing value becomes greater than 

 its fuel value, which at present averages 

 about $4 a ton, this material, too, will 

 be available for chemical processing. 



The total mill residue is equal in 

 weight to one-fifth of the national pe- 

 troleum production. Left unused in 

 the woods each year, because their re- 

 moval is considered unprofitable, are 

 44 million tons more of cut wood, 

 chiefly crooked, split, and partly de- 

 cayed material unsuitable for lumber 

 but admirably suited for chemical use. 

 Still another 23 million tons of stand- 

 ing timber are killed by fire, lightning, 

 or insects each year and left in the 



woods ; a large part of that would also 

 be suitable. Altogether, those residues 

 equal in weight about half the present 

 petroleum production. Enough wood 

 residues are available, then, to supply 

 a great new chemical industry. 



Such a large industry would not be 

 warranted unless its products were in 

 sufficient demand at a price for which 

 they could be profitably produced. 

 The nature and uses of the products 

 obtained by the various methods of 

 chemically processing wood can be a 

 measure of this demand and value. 



EXTRACTION differs from the other 

 chemical-processing methods in that it 

 is highly dependent upon species and 

 alters the wood substance only slightly. 

 The only extensive wood-extraction in- 

 dustry is the naval stores industry of 

 the South, which extracts turpentine 

 and rosin from old stumps of longleaf 

 and slash pines from which the sap- 

 wood has decayed. Only the heart- 

 wood stumps of those species are used 

 because of their high extractive con- 

 tent. The industry processes about 

 6,000 tons of stump wood daily to ob- 

 tain 12,500,000 gallons of turpentine 

 and 750,000 drums (520 pounds to the 

 drum) of rosin a year. Turpentine is 

 used chiefly as a paint thinner, a me- 

 dicinal, and a raw material for making 

 synthetic camphor and other valuable 

 synthetic products. The rosin is used 

 chiefly in soaps, paper size, paints, 

 varnishes, sealing waxes, cements, and 

 plastics. Large amounts of cymene and 

 a rosin residue are also obtained. The 

 latter is used in plastics and as a binder 

 for sand in foundry cores. 



Chestnut wood chips and hemlock 

 bark are extracted to obtain tannin for 

 tanning leather. In no case is the tan- 

 nin content of wood sufficient to make 

 extraction profitable for it alone. In 

 the case of chestnut, the extracted 

 chips have been used to form pulp for 

 paper making. The chip residue might 

 also be used for further chemical 

 processing. 



Years ago a small industry existed in 

 the Northwestern States in which the 



