Distiller's Cave (The Witcher 3: Wild Hunt)

On the Skellige Islands, on the very first island in the east, above the Grotto location, there is a cave. There I found a distiller's diary, a note on how to turn on the machine and a bag of malt. What do you need to do there, has anyone passed this place? There are two boilers, under one of which you can kindle a fire and two switches. The whole thing is highlighted in red. Is there a quest associated with this location?