From Gunpowder - Alchemy, Bombs & Pyrotechnics: The History of the Explosive that Changed the World by Jack Kelly
The author discusses the Confederacy's problems in obtaining saltpeter, an essential ingredient in the manufacture of gunpowder:
Faced with this bleak prospect, the Confederacy turned to George Washington Rains. Born in rural North Carolina in 1817, Rains had excelled at West Point and had taught chemistry there, resigning his commission in 1856 to become president of an iron works in nearby Newburgh, New York. Though he had lived half his life in the North, Rains chose allegiance to the slave states when war erupted. Confederate president Jefferson Davis put him in charge of what would soon be called the Gunpowder and Niter Bureau.
Rains knew that local producers could supply plenty of charcoal - he determined that cottonwood, more plentiful in the South than willow, worked just as well as a powder ingredient. Several hundred tons of sulfur, imported for sugar refining, were on hand at New Orleans. Adequate additional supplies could be acquired from sources in Texas.
Saltpeter was the critical item. Rains dispatched agents to Europe, and over the course of the war smugglers brought 2.7 million pounds of the salt through the blockade by which the Federals intended to strangle their enemies. Deposits derived from bat guano were dug from caves in Tennessee, Kentucky, and Alabama. To supplement these sources and to assure Confederate self-sufficiency in niter, Rains turned to the age-old practice of establishing saltpeter "plantations" or "nitriaries." Workmen dug long pits and filled them with stable manure, rotting vegetation, and animal carcasses. Stray dogs were rounded up and tossed in, prompting the Montgomery Weekly Mail to quip that "soldiers using this powder are said to make a peculiar dogged resistance."
Jonathan Haralson, a zealous official of the niter district around Selma, Alabama, insisted that housewives save the contents of their chamber pots to add to a collection barrel. Confederate soldiers composed a bit of doggerel to commemorate the proposal:
But you have put the pretty dears to patriotic pissing.
Not to be outdone, the Yankee troops replied:
If every time he shot his gun he used his sweetheart's nitre?
The Confederacy fell before much of this homegrown saltpeter, which took at least 18 months to ripen, found its way to rebel guns.