The volatility of HTC coals (hydrochar) from different biomass feedstock and model compounds was compared by thermogravimetric measurements. It is found, that lignocelluloses and its carbonisates behave significantly different than biomass with other composition. This is caused by the reduction of the cellulose carbonization due to the presence of lignin in lignocelluloses. In addition, HTC coals after thermal treatment were investigated. The chemical changes due to water elimination and cross-linking during carbonization and post-treatment were identified by FTIR measurements.