It wasn’t dried coffee it was called extract of coffee and had consistency of axle grease.
The coffee was brewed as normal, water was extracted from the brew and then added to Borden’s recently patented sweetened condensed milk. Packed in tins it was sent out to the troops who only needed hot water.
“Professor Tilden’s Extract of Coffee”, I found some info. Ha! Good stuff as far as that goes but I don’t believe it was extensively issued. Not anything like the bean coffee. The blockade really hit the Confederates the worst as far as coffee was concerned, they couldn’t hardly get any, not for love or money. They had some success getting Union supplies when the soldiers had to ditch their haversacks, and a lot of informal (and unauthorized) trading tobacco for coffee went on. Wonder what the exchange rate was?