In this study, hydrothermal carbonization (HTC) of grape seeds, a lignocellulosic biomass, was carried out at various temperatures (200, 225, and 250 degrees C), different reaction times (6, 12, and 24 h), and different biomass:water ratios (0.025, 0.05, and 0.1). The most important parameter affecting the yields and characteristics of hydrochars was found to be temperature. The HTC of grape seeds was then conducted in the presence of metal chlorides (i.e., CsCl, ZnCl2, and SnCl2) at temperatures of 200, 225, and 250 degrees C for 12 h. SnCl2 behaved very differently in the HTC process than the other catalysts (or no catalyst). A major difference among these catalysts was the extent to which they were incorporated within the hydrochar structure. SnCl2 was much more readily incorporated than was CsCI or ZnCl2. Carbon microspheres were observed in hydrochars from obtained biomass without a catalyst and with CsCl and ZnCl2 catalysts; agglomerated carbon nanospheres were observed in hydrochars produced with SnCl2. Hydrochars obtained at 225 and 250 degrees C by using SnCl2 and ZnCl2 catalysts were in the lignite class, while hydrochars obtained from biomass without a catalyst, and using CsCI, were in the peat coal class.