3500 



Chapter 28 



In special situations where diesel fuel is unavailable and where wood is 

 plentiful, wood gas can economically provide the energy necessary to drive 

 vehicles such as tractors. About 2.5 pounds of air-dry wood are required per 

 horsepower-hour compared to about 0.40 pound of diesel fuel. A cord of air-dry 

 hardwood should yield gas with energy equivalent to 125 to 150 gallons of diesel 

 fuel. 



A diesel tractor rated at 65 drawbar horsepower costs about $0.26 per horse- 

 power-hour of operation. If this tractor is modified to operate on wood gas, the 

 cost should be about $0.31 per horsepower-hour of operation (table 28-1). 



Table 28-1. — Estimated cost of owning and operating a 65 -hp (drawbar) diesel farm 

 tractor on diesel oil and wood gas (Post and Eoff 1981)' 



Diesel 



Wood gas 



Per year Per hour Per year Per hour 



Dollars 



Depreciation, tractor 900 1 .50 900 



Depreciation, gasifier, 



and cleanup equipment 



Interest, insurance, and taxes 1,190 1.98 



Filters, oil, and hydraulics 



associated with engine 



and drive train 306 .51 



Filters associated with 



burning wood gas 



Fuel 



Diesel ($1 .00/gal) 2,499 4. 16 



Wood ($30/dry ton) 



Labor cost 3,000 5.00 



Total cost 7,895 13.15 



Cost per horsepower-hour 



of operation"^ 0.26 



250 

 1,610 



306 



72 



198^ 



810 



3,450^ 



1.50 



.41 

 2.68 



.51 



.12 



.33^ 

 1.35 

 5.75' 



7,596 12.65 



0.31 



'Assuming $13,000 initial price, $4,000 salvage value, and 600 operating hours per year with 10- 

 year tractor life. 



^Some diesel fuel is needed for ignition of wood gas. 



^Assumes 15 percent increase in labor costs for wood gas operation. 



'^Assumes 50 horsepower output for diesel and 40 horsepower output for wood gas. 



