What type of decomposed plant material is typically used in the production of Scotch?

The production of Scotch whisky typically involves the use of peat, which is a type of decomposed plant material that forms in waterlogged areas known as peat bogs. Peat is rich in organic matter and has a unique ability to impart distinct flavors to the whisky when used during the malting process. Specifically, peat is burned to create smoke, which infuses the malted barley with a characteristic smoky flavor that is synonymous with many Scotch whiskies, especially those from the Islay region.

The other materials are not involved in this process in the same way. Sand, for instance, is primarily used in construction and does not contribute to the flavor profile of whisky. Wood, while significant in barrel aging, does not play a role in the initial stages of whisky production like malting. Coal is not typically used in whisky production and does not have the same flavor contribution as peat. Therefore, peat stands out as the correct choice for this question regarding Scotch whisky production.