This succinct thermodynamic study addresses the gasification chemistry (air/fuel ratio of 0.5) of four chemical elements involved in ash-related challenges, i.e. Na, K, S and Cl. At typical temperatures for the process studied, the following main trends have been observed: (1) the phase distribution of these elements may change abruptly, i.e. within a narrow temperature range; (2) the main practical outcome of point 1 is that it will be difficult to optimise a given process giving the versatility of chemistry vs temperature but stable operating conditions are preferable. Methods exist to abate ash-related challenges but their selection should include both practical and economic considerations.