Characterization of hydrochar obtained from hydrothermal carbonization of wheat straw digestate

Abstract

Hydrothermal carbonization (HTC) of wheat straw digestate was performed at 180–260 °C for 2–8 h. The resulted hydrochars were analyzed by ultimate analyzer. Elemental carbon and oxygen concentration of hydrochars were fitted with power law correlation. Moreover, chemical structures of feedstocks and hydrochars were investigated by 13C cross-polarization magic angle spinning (CP/MAS) nuclear magnetic resonance (NMR) spectroscopy. In particular, a procedure including CP dynamics analysis was applied to obtain semi-quantitative information on the composition of the analyzed materials from 13C CP/MAS spectra. Up to a process temperature of 220 °C, digestate-derived hydrochar contained primarily crystalline cellulose and lignin. At 260 °C, crystalline cellulose was degraded and more aliphatic carbon and lignin-rich hydrochars were produced. Ester bands corresponding to hemicellulose disappeared at mild HTC conditions at 180 °C and 2 h.