Combine pomegranate juice and demerara sugar in a saucepan and place over medium-high heat.

Stir until the sugar is completely dissolved, about 5 minutes, and set the pan aside to cool.

Express the oil from the citrus zests into the pan, and drop the peels into the liquid.

Once cool, remove the peels from the liquid and store the grenadine in an airtight container in the refrigerator for up to 1 month.