You're left with a much smaller volume of willow wood than the original soil. Wood that could be then be dried to reduce its weight even more. It could then be

You're left with a much smaller volume of willow wood than the original soil. Wood that could be then be dried to reduce its weight even more. It could then be used as a biofuel in a fluidized bed reactor specifically created to handle such heavy metal dense fuel, as suggested in this paper.[1] Most of the heavy metals remain in the ash, the cadmium needs to be trapped in the exhaust. 1 - https://sci-hub.se/https://doi.org/10.1016/j.biombioe.2011.12.025