What food item became currency for the trade system among the confederate prisoners?

Most people don't consider rats a food item, but if they were among the over 400,000 soldiers held prisoner during the U.S. Civil War, they might change their mind. Desperation led to desperate schemes in POW camps in both the North and the South. One soldier at  Camp Lawton, near Millen, Georgia, wrote that prisoners were “obsesses with food, sometimes consuming rats or boiling grass to ward off scurvy” (quoted in CNN.com/us/civil war/150th anniversary-prisons).

Of all the prison camps, Andersonville Prison in the Confederate State of Georgia is the most well known, and it was considered the worst of all camps. About 45,000 soldiers went through Andersonville. The peek population, in a prison built to house only 10,000, was over 33,000. And when the prisoner swap between the Northern and Southern Armies stopped because the South refused to exchange “negro troops the same as white soldiers,” the overcrowded conditions continued (civilwar.org). Food was scarce for everyone in the prisons, prisoners and guards alike. However, the guards were fed more of the scarce rations than the prisoners, so prisoners ate whatever they could find — including rats. Lack of adequate food, medical care, and sanitation took the lives of many at the Andersonville Prison Camp.

Overcrowding was an issue in almost all prison camps during the war, in both the North and the South. Thus, insufficient food was also a problem for overcrowded Northern POW camps. The Elmira Camp in the Union State of New York, with barracks space for only 5,000, had 12,000 prisoners residing there between July 6,1864, and July 11,1865. Hence, the prisoners in Northern camps also ate whatever they could find. Rats were a big problem at the camps, so the Elmira Camp officials used a small dog to catch rats that they then sold to prisoners for 5 cents. Most of the Confederate soldiers could not afford the 5 cents, though, leading two Elmira prisoners to capture the dog and cook it. They were, of course, sent to the guardhouse for 30 days for punishment.

Countless soldiers on both sides died from malnutrition and disease, especially since there was little medical care available. At Elmira about one-fourth (3,000) of the prisoners died. At Andersonville, over 12,000 died (almost as many as the whole prison population at Elmira). Approximately 56,000 deaths, nearly 10% of the total Civil War death toll, were due to the horrible conditions in prison camps.