Measures and yields of products and residues jDlI 



convert a much lesser proportion into primary product. The material flow dia- 

 grams in chapter 28 permits ready comparison of utilization in a wide range of 

 products. 



Chapter 18 discusses the efficiency of various sawing methods and chapters 

 22 through 26, a wide range of products. 



Readers needings a model to calculate the lumber and residue production at 

 any sawmill — operating or proposed — with a minimum of data collection are 

 referred to Steele and Hallock (1979). Their geometric model estimates volumes 

 of green lumber, dry lumber, green chips, green sawdust, and dry planer 

 shavings. 



Average residue production at Georgia sawmills was reported by Page and 

 Baxter (1974) as follows: 



Residue/Mbf of lumber manufactured 

 Type of residue Hardwood Softwood 



Tons - 



Bark (green weight) 0.44 0.44 



Chips (green weight) 1.49 2.51 



Sawdust (green weight) 1 .09 0.44 



Shavings (dry weight) 0.27 0.48 



A canvass of mills in Florida, the Carolinas, and Georgia (Welch and Bellamy 

 1976) indicates the following utilization proportions in lumber and veneer pro- 

 duction (data based on 893 sawmills and 97 veneer mills): 



Proportion of log 

 Mill type volume input ending Proportion of 



and species class as primary product residues utilized 



Percent 



Sawmills 



Hardwood 56 76 



Softwood 37 89 



Veneer mills 



Hardwood 60 79 



Softwood 45 91 



For all 1,102 mills in the study (including those that produced pulp, treated 

 wood, or specialty wood), an average of 86 percent of the initial wood residues 

 was utilized in 1973-74 as opposed to only 37 percent in 1962. Utilization rates 

 varied by species type and by type of residue. Less than 1 1 percent of the 

 softwood residues was wasted, but almost 24 percent of the hardwood residues 

 was not used. Almost all of the coarse residues and planer shavings were 

 utilized; over 35 percent of the finer residue was not. In addition, all but 25 

 percent of the bark residue was put to some use, mainly for industrial fuel. 



A study of 25 Arkansas mills (Porterfield 1975) suggested that utilization 

 efficiency is related more to sawmill size than to species sawn. Large and small 

 mills produced from 55 to 62 percent of their total output as green lumber, but 



