Barley malt is an ingredient used in brewing, a division of the cooking skill. Barley malt can be made by cooking barley on a range. Barley can be grown from exceedingly common barley seed at a very low farming level, and can be protected by farmers for the price of three buckets of compost. "Cooking" barley can only be done on a range, and gives no cooking experience.
Barley malt is a critical ingredient in brewing. All types of ale require barley malt as an ingredient (Note that Cider is not an ale). To start brewing, a player must first go to one of the brewing vats located in either Keldagrim or Port Phasmatys. After adding two buckets of water to the brewing vat, a player must add two barley malt items to the vat, followed by the deciding ingredient and ale yeast.
The other use for barley malt is a farming payment to protect a patch of jute, in exchange for 6 of this item.
It's needed for the Forgettable Tale... Quest.