Manurial Value of Sewage 127 



of sewage by chemical means has been found unprofitable 

 on account of the slight concentration of the liquid their 

 utilization for crop growth is occasionally found profitable 

 on sewage-farms. Profitable sewage-farming is, however, 

 exceptional. By far the greatest number of sewage- 

 farms do not yield a profit. Especially is this the case 

 when the initial outlay for land and equipment is in- 

 cluded in the charges. The failure of sewage-farms to 

 return a profit is not difficult to understand if we remem- 

 ber that the land near large cities is very costly, that 

 large areas are required for sewage treatment, and that 

 the range of crops grown is frequently limited. More- 

 over, the proportion of manurial constituents in sewage 

 is, after all, so slight as to make the application of very 

 large quantities necessary in order that an adequate 

 supply of plant-food may be furnished to the soil. At 

 a generous estimate, English sewage may be allowed 

 a value of three or four cents per ton; while American 

 sewage cannot be valued at much more than a cent per 

 ton on the basis of its manurial ingredients. " As Profes- 

 sor Anderson suggested long ago," says Storer, "it 

 would be about as reasonable to expect the farmers to 

 manure their land with the smoke of cities as with 

 sewage; for, as every one knows, enormous quantities 

 of ammonia must be lost in the aggregate from cities 

 where domestic fires are fed with soft coal. But precisely 

 as it is with the smoke, so it is with sewage; that is to 

 say, the fluid is so very dilute that it cannot be put to 

 use." 



Sanitary value of ^sewage-irrigation. While sewage- 

 irrigation 'has little to recommend it from the economic 



