Rice hulls are the outer, protective coverings of rice grains. They are an inert ingredient, meaning they don’t contribute flavor, color, or aroma to the beer, but they play a crucial role in the brewing process, especially when brewing with a high percentage of adjunct grains or grains that lack husks, such as wheat or oats.

The primary purpose of using rice hulls in brewing is to prevent a stuck sparge. A sparge is the process of rinsing the grain bed to extract as much sugar as possible from the malted grains. Sometimes, due to the gelatinous nature of some grains, the grain bed can become compacted, and the flow of water through the bed can be restricted, leading to a stuck sparge. This is particularly common in beers with a high proportion of wheat, oats, rye, or other adjuncts.

Rice hulls help in the following ways:

1. Preventing Stuck Sparge: By mixing rice hulls into the grain bed, brewers can ensure a smoother flow of water through the mash, preventing the grain bed from compacting and thus avoiding a stuck sparge.

2. Filter Aid: Rice hulls act as a natural filter aid, helping to clarify the wort as it passes through the grain bed.

3. Efficiency Improvement: The use of rice hulls can also aid in improving lautering efficiency by facilitating better drainage and reducing the risk of channeling within the grain bed.