Green’s Dictionary of Slang

Free State coal n.

(S.Afr.) dried cow-dung, used as fuel.

Fort Beaufort Advocate 2 Oct. n.p.: Somebody was asking what Free State coal is [...] according to [Dictionaries] it is a South African term for dried cow-dung. Cow dung is used for fuel where wood is scarce, but why the honour went to the Free State . . is a mystery [DSAE].