I've posted a thread on that:
https://civilwartalk.com/threads/confederate-troops-recycling-bullets-and-shells.118733/
A few accounts....
Pvt. Frank H. Foote, 48th Mississippi Infantry, during the siege of Petersburg:
"Shells flew overhead pretty thick, and afforded a source of revenue to the poor Confederate soldier, which in those hard times was indeed a God send; and that was gathering of iron fragments of bursted shells and the leaden balls that fell behind our lines in vast quantities and selling them to the junk dealers at Petersburg, who bought them up for the C.S. Government. It was no unwonted sight to see dozens of ragged Confederates digging, gouging, and gathering to themselves the precious fragments in heaps from the fields to our rear. Thousands of pounds of each were thus gotten, and disposed of at good figures; and the iron showers that bursted over-head proved a blessing in this respect; and brought sustenance to man, where it was intended to wreak destruction. The government had it worked over into shell and bullets which would be sent to us; and thus it returned to our foe to make death or be lost in the pines. The soldiers finally became so reckless that frequently orders had to be issued forbidding the men to gather the iron. I have seen dozens of soldiers racing after a huge mortar shell; they knew about where it would drop, and recklessly exposed themselves to secure the shell or its pieces. These shells would frequently not burst, and this was a prize eagerly striven for, as it realized about thirty dollars."
Pvt. Philip D. Stephenson, 5th Co. Washington Artillery, at Spanish Fort:
"Another recreation during the early part of the siege was to gather bullets and other forms of lead in the open space behind us. This lead was sent back to Mobile for remanufacture into cartridges and he who gathered a certain amount got a furlough of a day or so into the city. The soldiers did not hesitate to risk their lives while not in action roaming around in the exposed open space behind us gathering bullets. A furlough was a furlough."
Maj. Gen. Samuel G. French during the Atlanta Campaign:
"28th. [August 28, 1864] I rode through the city [Atlanta]. To give you can idea of the terrible musketry fire, in an open field between their picket line and mine one brigade picked up about five thousand pounds of lead balls that had been fired on the lines. The ground was literally covered with them--oxidized white like hailstones. Trees three and four inches in diameter in front of my line were cut down by balls. The lead was sold to the ordnance officers, and the weight was thus known."