There's probably a little THC still captured inside the tar. You could dry the lungs out in natural sunlight (oven would be too hot, unless at a very low setting), til their are crispy. Cut them into small pieces, about the size of tortilla chips. Grind them up in a coffee grinder LIGHTLY until its the same consistency of well-ground pot. Look up construction of a butane honey-oil extraction device (basically a PVC pipe with the ends capped and a hole drilled in each end), make one, and stuff the lung inside. Extract like you normally would during a regular butane extraction of marijuana.