Preparation of Iron-Containing Digestate-Based Biochar and Its Impacts on Anaerobic Digestion Performance of Urban Organic Solid Wastes
LIU Mengyao
HE Xin
ZHAO Zhiqiang
Abstract：Direct interspecies electron transfer(DIET)offers a faster electron transfer rate and a reduced dependence on diffusive mass transfer,potentially becoming a primary mechanism for the anaerobic digestion of urban organic solid wastes,such as food waste and excess sludge.However,digestate,the byproduct of anaerobic digestion,poses environmental hazards and hinders the achievement of a waste-free city.This study investigates the morphological and structural characteristics of iron-containing digestate-based biochar(Fe-BC)produced at various carbonization temperatures,and its impact on the anaerobic digestion of urban organic solid wastes,with the goal of achieving"waste-to-value-added products".The results showed that increasing the carbonization temperature led to a more developed pore structure in the Fe-BC,but reduced the complexity of its functional group composition.Fe-BC prepared at 800 ℃ exhibited the most developed pore structure and the highest iron content,with more uniform iron distribution throughout the biochar.In anaerobic digestion experiments,the group with biochar prepared at 800 ℃ demonstrated a cumulative methane yield of 184.24 mL/g volatile solids(VS),a 19.78％increase compared to the control group(without biochar).The VS removal rate reached 45.75％,a 6.73％increase over the control group.The group with biochar prepared at 500 ℃ showed a 15.66％increase in cumulative methane yield and a 5.79％increase in the VS removal rate,while the other experimental groups showed no significant improvement.The effect of Fe-BC on promoting methane production was most pronounced in the middle of the experiment,peaking on the ninth day.Furthermore,Fe-BC prepared at 800 ℃ improved both the methane content and the quality of the biogas produced.Electrochemical analysis indicated that the sludge in the Fe-BC group prepared at 800 ℃ exhibited greater capacitance and lower electrical resistance,suggesting enhanced interspecies electron transfer,microbial electron exchange,and electrical conductivity.Additionally,Fe-BC increased the relative abundance of Methanosaeta and Fastidiosipila.In conclusion,Fe-BC derived from digestate possesses a well-developed pore structure,with Fe-BC prepared at 800℃ exhibiting the most developed porosity.The addition of Fe-BC prepared at 800 ℃ was the most effective in promoting the anaerobic digestion of urban organic solid wastes.Moreover,Fe-BC enriched specific microorganisms,thereby promoting DIET and enhancing the anaerobic digestion of urban organic solid wastes.
Keywords：Municipal organic solid wastesAnaerobic digestionIron-containing digestateBiocharDirect interspecific electron transfer
Publication Date：2025-10-30
Online Publishing Date：2025-10-20(First online date of this platform, not the publication date of the document)
Pages：10( 181-190 )