Put the water, sweet potatoes, chickpeas, onion, rice, garlic, and salt in a large saucepan and bring to a boil over medium-high heat. Decrease the heat to medium-low and cook, stirring occasionally, for 45 minutes.
Put the peanut butter in a small bowl. Add ½ cup of the liquid from the stew and stir well to make a smooth paste. Stir into the stew along with the collard greens and cook