Ọ na-adabara na saịtị dị ize ndụ nke nwere methane (nke a na-akpọkarị gas) na mgbawa coal0ust, nke nwere ike ijikwa nsị nke nwere ngwakọta nke ọdịnaya siri ike dị ka sedimenti, coal slime, cinders, fibrous material, etc.
