RAAB is an old Terra Preta System as practiced in parts of India, which is no more seen. Mr. Bernard Declercq, Auroville had seen this system about 30 years
back, in parts peninsular India, explains it as "Raab is a system of charring biomass used by some tribal communities in India. It consists of making beds of various layers of dry,
half-dry and fresh woody and leafy biomass, dung and clay. The thus layered bed is fully sealed with clay and cold fired (burning in reduced conditions). In the resultant residues rice nurseries are started. The tribals affirm that this gives perfect growth to the rice plants. Charcoal bits, ash, even wood vinegar as well as sulfur that may have been absorbed by the clay, would explain the growth enhancing factors of the raab system". He is practicing Terra Preta and also charcoal production at Auroville. Please see this link.