Taking them to a crossroads would be ideal for this, because of all the symbolism.
If they’re giving off energy you can take them to an open window and cast the energy out using the hand gestures below, visualise it flying out of the window and dispersing into the sky, and then wrap the physical remains in tinfoil (aluminium baking foil) or keep them in a tin, sealed in metal, until you’re able to dispose of them properly.