Improvement in the physicochemical characteristics of biochar derived from solid digestate of food waste with different moisture contents

The management of digestate from food waste (DFW) has become a worldwide challenge. Pyrolysis is a promising technology to generate biochar from the DFW. However, unlike other biomass, DFW usually has high salt and moisture content, which affects the properties of biochar generated from pyrolysis. The characteristics of biochar derived from DFW with different MCs (5%, 20%, 40%, and 60%) were investigated in the present study. It was found that more micropore and mesopore structures were generated in the biochar with the increase of MC from 5% to 60%, resulting in the Brunauer-Emmett-Teller surface area of the biochar increased from 89.23 m(2) g(-1) to 117.75 m(2) g(-1). The MC could also promote the variation of oxygen-containing functional groups and the generation of amorphous carbon structures, which are beneficial for the adsorption property of the biochar. Pyrolysis could stabilize the metals in the biochar, while MC has little effect on the metal speciations. These results provide fundamental information on the impact of MC on the properties of biochar derived from DFW and are important for the optimization of the pre-drying process.

Automated summary

The management of digestate from food waste (DFW) is a global challenge. Pyrolysis is a promising technology for producing biochar from DFW. However, the high salt and moisture content in DFW affects the properties of biochar generated. This study found that increasing moisture content resulted in more micropore and mesopore structures in the biochar, increasing the surface area. Moisture also promoted changes in oxygen-containing functional groups and the formation of amorphous carbon structures, enhancing the adsorption properties of the biochar. Pyrolysis stabilized metals in the biochar, unaffected by moisture content.