<p>This study investigated the impact of biochar on the semi-continuous anaerobic thermophilic digestion of kitchen waste and subsequent dewaterability of the digestate. Two biochar types were prepared from banana peels (BBP biochar) and spent coffee grounds (BCG biochar), and then applied as additive materials. Both biochars increased the production of methane from kitchen waste with the maximum yield of nearly 400 L_CH4/kgVS. However, stable digestion performance was only achieved using BBP, which was characterized by lower hydrophobicity and greater polarity than BCG. Furthermore, the digestate from the experiment with BBP displayed much better dewatering properties, as evidenced by much lower capillary suction time (CST) than the values reported in the BCG and control processes. The digestate dewaterability was further improved by using cationic flocculant and inorganic coagulants for conditioning with the most effective iron-based PIX113, which efficiently clarified supernatant. In conclusion, it has been documented that biochar added to kitchen waste before digestion not only increased biogas production but also improved the digestate dewaterability, however, the effect was dependent on the origin and properties of this supplement.</p>