GST classification: Other slag and ash, including seaweed ash and municipal incineration residues subject to GST. Goods classified as other slag and ash, including seaweed ash (kelp), and ash and residues from the incineration of municipal waste (other than fly ash) are covered in Schedule 3 for GST, the entry having been amended by notification no. 43/2017 w.e.f. 15-11-2017 to adopt the current descriptive scope.