木灰 is read as きばい (kibai) and means wood ashes.
きばい
kibai
こぼくしかい
withered trees and cold ash
きわた
cotton (material)
こがらし
cold wintry wind
もくぞう
wooden
もくざい
lumber
きずみ
charcoal
もくへん
block (of wood)
もくせい
Jupiter (planet)
きど
entrance to an entertainment venue (i.e. sumo arena, etc.)
もくはん
wood-block printing
もっかん
wooden bobbin
もくほんしょくぶつ
woody plant