Nordic countries incinerate almost all non-recycled municipal waste, to the point that they import waster from other countries to keep the incinerators well fed

Nordic countries incinerate almost all non-recycled municipal waste, to the point that they import waster from other countries to keep the incinerators well fed. Any insights how this is handled there? They are pretty famous for having some of the strictest environmental and health regulations, so I assume these issues have solutions.