Why were slaves so valuable to the wartime economy of the Confederacy?

Slaves were very valuable to the wartime economy of the Confederacy. With slaves doing the work on the farms, the farm owners were able to go and fight for the Confederacy. These farm owners knew that their farms could operate and be productive even if they weren’t present on the farms, because they knew the slaves could be made to continue to work and to harvest the crops. Since 89 percent of eligible white Southern men served in the Confederate army, the work that the slaves did on the farms was very important.
Slaves were also used in other ways. Some were used in industries. They replaced the workers who went to fight in industries such as the iron and salt industries or in building railroad lines. For example, many slaves made up a majority of the workforce at Richmond’s Tredegar Ironworks, a company that produced cannons for the Confederacy during the Civil War. Some slaves were used as cooks and nurses for the Confederate army. Some slaves also helped to build the defenses around some of the Southern cities such as Richmond and Petersburg.
The presence of slaves in the South allowed the Southern economy to continue to function during the Civil War.
https://historyplex.com/slavery-during-civil-war

https://www.encyclopediavirginia.org/Slavery_During_the_Civil_War

https://www.virginiahistory.org/collections-and-resources/virginia-history-explorer/american-turning-point-civil-war-virginia-1/how