EXPERIMEXTAL PRODUCTION OF STRAW GAS. 7 
lampblack, it is doubtful whether a market for this residue or the 
other by-products would yield a profit to the farmer. The cost of 
collecting, hauling, and shipping, as compared with the prices these 
products command, would make such a procedure unprofitable. 
The most advantageous utilization of the by-products probably 
is on the farm where the grain is produced. As a fuel the carbon 
residue has a heating value of approximately 10,000 British thermal 
units per pound, while as a fertilizer its average composition is 
about 5 per cent potassium oxid (K 2 0) , 1.5 per cent ammonia (XH 3 ) , 
and 0.3 per cent phosphoric acid (H 3 P0 4 ). The tar can be used 
satisfactorily as a wood preservative and disinfectant. 
IMPRACTICABILITY OF EXPERIMENTAL PLANT. 
The results of the tests here reported indicate that the type of 
straw-gas producing plant used is not practicable as a unit for 
farms, chiefly on account of its initial cost and upkeep, the length 
of time required to produce suitable quantities of gas, and certain 
inconvenient features of the retort and scrubber. 
In conducting an average run on the production of gas, about 75 
pounds of unbaled straw can be placed in the retort as a maximum 
single charge. Considering the time necessary for charging the 
retort, carbonizing, cooling, and removing the charge, approximately 
1J hours are required for the distillation of this quantity of straw, 
yielding about 375 cubic feet of purified gas. The complete cost 
of the plant as installed, exclusive of building, was $1,500. 
The annual cost of producing gas in this plant is shown in Table 2. 
Table 2. — Cost of producing straw gas in experimental plant* 
Interest on investment (6 per cent on .$1.500) $90.00 
Depreciation (8 per cent) 120.00 
Labor for producing gas (1,000 man-hours at $0.50 per 
hour) 500. 00 
Total 710. 00 
On this basis, 4.22 cubic feet of gas can be produced for 1 cent, or 
1,000 cubic feet for $2.36. In terms of heating units, the gas pro- 
duced for 1 cent represents 1,688 British thermal units. 
In the foregoing computations no charge has been made against 
the straw consumed, no monetary value has been given the by- 
products, and no consideration has been given to hauling charges, 
or to the cost of a building for housing the equipment. The heat 
for carbonizing the charge was supplied by straw burned in the 
fire box. Straw, generally wasted in many sections, has a distinct 
potential value by virtue of the fertilizing constituents which it 
contains. According to figures 5 taken from accurate analyses, with 
nitrogen selling for 25 cents, phosphoric acid for 8 cents, and potash 
for 15 cents a pound, oat straw has a value of $7.73. barley straw 
one of $6.68. wheat straw one of $1.95. and rye straw one of $5.25 
a ton. It would be necessary to pay these prices to obtain the same 
quantity of fertilizing constituents in commercial fertilizers. Ac- 
cordingly, straw when returned to the soil for the addition of plant 
food elements is very valuable. 
i Yearly production of ga^, 300.000 cubic feet. 
5 Fertilizing Value of Straw. Farm Implement News. vol. 40. no. 4t'» (Nov. 13, 1919 . 
p. 27. 
