3518 Chapter 28 



is best adapted to steep slopes and yields from 20 to 25 tons per operating hour. 

 The swathe-felling mobile chipper operates best on stone-free level ground and 

 can produce 12.5 to 20 tons per hour. The conventional system averages 25 to 30 

 tons per hour on flat to moderate slopes. Productivity depends on stand condi- 

 tions such as tree size, volume per acre, and tract size. Whole-tree chipping, and 

 particularly the swathe-felling mobile chipper, leaves the site very clean and 

 substantial site preparation savings can result. Continuing commercial field 

 trials of the mobile chipper should engender design improvements and increased 

 productivity. 

 Key comparative statistics for the three systems are as follows (1980 basis): 



Conventional 

 whole-tree Cable-yarder Swathe-felling 



Statistic chipper chipper mobile chipper 



Initial capital investment, dollars 663,000 975,000 603,000 



Annual production, tons/year 

 (green-weight basis) 



High 50,400 42,000 30,000 



Low 42,000 33,600 18,750 



Employees number 8.5 15 6.5 



Fuel consumption, gallons/year 63,950 1 10,468 50,423 



Total annual costs, dollars/year 



(with 15 percent cost of capital) 474,607 694,529 426,499 



Production cost, dollars/ton 



High 11.30 20.67 22.75 



Low 9.42 16.54 14.21 



Total annual costs, dollars/year 



(with 30 percent return on investment) 528,245 777,085 474,608 



Production cost, dollars/ton 



High 14.14 26.50 29. 12 



Low 12.01 21.20 18.20 



28-10 $700,000— MANUFACTURE OF CHARCOAL, OIL, 

 AND GAS WITH A PORTABLE PYROLYSIS PLANP^ 



The Enerco® model 24-D pyrolysis unit (fig. 28-12), in which hot pyrolytic 

 gases are recirculated through the reactor — sometimes termed converter, was 

 mounted on a 35-foot trailer and operated for 200 hours by the Tennessee Valley 

 Authority to obtain data for commercial operations. Air, with its nitrogen, is 

 kept out of the system to diminish nitrous oxides and other nitrogenous material 

 in resulting pyrolysis gas and oil, thereby reducing their corrosiveness. Moisture 

 content of wood chips entering the converter should not exceed 20 percent (wet- 

 weight basis). 



^ ^Abstracted from Klein (1981). 



