The burnt shrimp has no use whatsoever, although you can unsuccessfully attempt to eat it. Like most other burnt food, it is tradeable to other players but not on the Grand Exchange. When Tutorial Island existed, the first shrimp cooked was always burnt. Prior to the release of Swan Song, burnt raw shrimp became the same type of burnt fish as anchovies, instead of their own item. A hidden update on 4 March 2013 made all burnt shrimp stackable.