I was being very brief.
After the material has been converted into fuel, the mineral residue must be returned to the ecosystem from which it came. This can be done at the same time, and by the same vehicles that are picking up the litter. As these vehicles vacuum an area in the front, they spray the mineral residue from the rear to replace those minerals contained in the stuff being removed. On farms, after conversion, the residue is applied to the fields as fertilizer.
David F Mayer