One hundred lbs. of fresh fæces contain 75 lbs. of water, and 25 lbs. of dry substance.
One hundred lbs. of fresh urine contain 96½ lbs. of water, and 3½ lbs. of dry substance.
One hundred lbs. of the dry substance of the fæces contain 5 lbs. of nitrogen, and 5½ lbs. of phosphates.
One hundred lbs. of the dry substance of the urine contain 27 lbs. of nitrogen, and 10¾ lbs. of phosphates.
These figures are from Lawes and Gilbert, and may be taken as representing the composition of excrements from moderately well-fed persons.
According to Wolff, a ton of fresh human urine contains 12 lbs. of nitrogen. According to Lawes and Gilbert, 18 lbs.
The liquid carted from the city by Mr. Hooker was from well-fed adult males, and would doubtless be fully equal to the figures given by Lawes and Gilbert. If we call the nitrogen worth 20 cents a lb., and the phosphoric acid (soluble) worth 12½ cents, a ton of such urine would be worth, on the land, $1.06.
“A ton of the fresh fæces,” said the Deacon, “at the same estimate, would be worth (20 lbs. nitrogen, at 20 cents, $4; 21¾ lbs. phosphoric acid, at 12½ cents, $2.70), $6.70.”
“Not by a good deal,” said the Doctor. “The nitrogen and phosphoric acid in the urine are both soluble, and would be immediately available. But the nitrogen and phosphoric acid in the fæces would be mostly insoluble. We cannot estimate the nitrogen in the fæces at over 15 cents a lb., and the phosphoric acid at 5 cents. This would make the value of a ton of fresh fæces, on the land, $4.09.”
“This makes the ton of fæces worth about the same as a ton of urine. But I would like to know,” said the Deacon, “if you really believe we could afford to pay $4 per ton for the stuff delivered on the farm?”