BuildASoil Par Boil Rice HullsPar Boiled Rice Hulls by the bale or truckload. PBH Brand Approved for Organic Use. Studies have proven that rice hulls can efficiently replace perlite in your potting soil mixes and is much better for the environment. We have independently heavy metal tested the contents and will only work with PBH for our rice hulls because of how clean they have tested. Beware of cheap rice hulls potentially full of heavy metals. Parboiled rice hulls are produced