Pyrolysis behaviors and thermodynamics properties of hydrochar from bamboo (Phyllostachys heterocycla cv. pubescens) shoot shell

•Bamboo shoot shell was employed to produce hydrochar.•Pyrolysis and thermodynamics properties followed dose-response function.•Rapid variations of the hydrochar properties appeared at severity of 5.93–6.59.•Hydrochar thermal stability increased greatly with the increase of severity.•Thermodynamic properties of hydrochar approached those of lignin model compounds. Hydrothermal carbonization (HTC) was employed to produce hydrochar from bamboo (Phyllostachys heterocycla cv. pubescens) shoot shell (BS) at severity (combined temperature and time) of 4.83–7.69. The pyrolysis and thermodynamics properties of the hydrochars were fully investigated. The results showed that the hydrochar properties (solid yield, C content, H/C and O/C atomic ratios, pyrolysis yield, pyrolysis index, formation of enthalpy, exergy, LHV, and HHV) of BS were highly dependent on severity and could be expressed by dose-response functions. The rapid variations of the hydrochar properties appeared at severity of 5.93–6.59. The pyrolysis temperature interval for the maximum weight loss shifted from 300 to 400°C at hydrothermal severity less than 6.59 to 400–500°C at hydrothermal severity greater than 6.59. The hydrochar thermal stability increased greatly with the severity increasing. And the thermodynamic properties of hydrochar approached those of lignin model compounds as the hydrothermal severity was greater than 6.59.