starch . Some briquettes may also include  brown coal  (heat source), mineral carbon (heat source),  borax ,  sodium nitrate  (ignition aid),  limestone  (ash-whitening agent), raw  sawdust  (ignition aid), and other additives like  paraffin  or  petroleum solvents  to aid in ignition. [6] Extruded charcoal  is made by extruding either raw ground wood