Pelletization of nitrogen-containing biowaste hydrochar for solid biofuel preparation

In this study, typical N-containing biowaste including food waste (F), sludge (S), and chlorella (C) was modeled using pine (P) as a carbohydrate component and protein/glycine as a nitrogen-containing component, and hydrothermal carbonization and pelletization were performed to in-vestigate the fuel properties of hydrochar pellet including proximate analysis, elemental compo-sition, tensile strength, and combustion characteristics. Results suggested that the introduction of N can obviously enhance the compressive strength of hydrochar pellet, of which chlorella model derived hydrochar pellet possessed higher tensile strength (1-3.75 MPa) compared to others. Protein/P model hydrochar had a higher water resistance index, but glycine/P model hydrochar had higher hydrophily than that of protein/P model. Most importantly, H/C in all protein/P model hydrochar was lower than that of glycine/P, and bio-oil derived liquid bridge may ac-count for the high tensile strength. Moreover, combustion analysis showed that glycine in model enhanced volatile matter combustion of hydrochar with a low ignition temperature. This work suggested that N in biowaste had significant effect on the fuel properties of hydrochar pellet, and proper strategy of N-containing biowaste for HTC can be expected for the value-added utilization as solid biofuel.

Automated summary

In this study, the fuel properties of hydrochar pellets derived from various N-containing biowastes were investigated through hydrothermal carbonization and pelletization. The introduction of N significantly enhanced the compressive strength of hydrochar pellets. Chlorella-derived hydrochar pellets exhibited the highest tensile strength. Protein/P model hydrochar had a higher water resistance index, while glycine/P model hydrochar was more hydrophilic. The N-containing biowaste had a significant effect on the fuel properties of hydrochar pellets, offering potential for value-added utilization as solid biofuel.