Rice husk coal or carbonized rice husk, (Khuntan燻炭 / Ibushisumi) is a excellent soil improvement material. It improves drainage, allows the soil to breathe, and is the habitat of microorganisms that also improve the soil. Rice husk coal has an alkaline pH of 8-9, that when added to acidic soil, helps to enhance the disease resistance of vegetables. The lightweight coal can easily be added to potting mixes or used alone as a cover crop to prevent weeds.
*tomononekko.blog - DIY Khuntan. Guide to making Rice husk coal.