Disposing of empty fruit bunches (EFBs) is an important problem in the palm oil production industry. Although part of an EFB is used as boiler fuel and fertilizer, most of it goes to waste, and consequently, the valuable energy contained in the woody waste is not utilized in the energy cycle. Herein, we examine EFBs as a fuel. EFBs were treated under hydrothermal conditions between 423 and 623 K without a catalyst to produce charcoal, which was subsequently compared with carbonization under dry nitrogen conditions. The hydrothermal conditions at 573 K and dry conditions at 873 K had similar charcoal yields of 31.4% and 27.8%, respectively. However, the calculated heating value of charcoal obtained from the hydrothermal conditions at 573 K was high (25.8 MJ/kg) compared to that obtained from the dry conditions at 873 K (22.0 MJ/kg). The FT-IR spectra showed that increasing the reaction temperature promoted carbonization of EFBs, and the intensity of the peak due to the -OH of EFBs became weak. Hence, carbonization of EFBs is promoted at low temperature under hydrothermal conditions compared with dry conditions.