Hydrochar-Facilitated Anaerobic Digestion: Evidence for Direct Interspecies Electron Transfer Mediated through Surface Oxygen-Containing Functional Groups

Acceleration of the anaerobic digestion (AD) process is crucial to achieving energy-efficient recycling of organic wastes. Hydrochar is produced by hydrothermal liquefaction of biomass, yet its application in the AD process is rarely reported. The present study showed that sewage sludge-derived hydr...

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Published inEnvironmental science & technology Vol. 54; no. 9; pp. 5755 - 5766
Main Authors Ren, Shuang, Usman, Muhammad, Tsang, Daniel C. W, O-Thong, Sompong, Angelidaki, Irini, Zhu, Xiangdong, Zhang, Shicheng, Luo, Gang
Format Journal Article
LanguageEnglish
Published United States American Chemical Society 05.05.2020
Subjects
Acetic acid
Acidification
Activated carbon
Algae
Anaerobic digestion
Anaerobic processes
Carbon dioxide
Diet
Electrical conductivity
Electrical resistivity
Electron transfer
Energy efficiency
Functional groups
Hardwoods
Liquefaction
Methane
Methanogenesis
Methanosaeta
Organic wastes
Oxygen
Poplar
Refuse as fuel
Sewage sludge
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Summary:Acceleration of the anaerobic digestion (AD) process is crucial to achieving energy-efficient recycling of organic wastes. Hydrochar is produced by hydrothermal liquefaction of biomass, yet its application in the AD process is rarely reported. The present study showed that sewage sludge-derived hydrochar (SH) enhanced the methane production rate of glucose by 37%. SH increased the methane production rate from acetate but did not affect acidification and the methane production rate from H2/CO2. SH enhanced hydrogenotrophic methanogenesis, which could be due to direct interspecies electron transfer (DIET) by converting H+, e–, and CO2 to methane. Trichococcus and Methanosaeta were dominant in the AD process with SH. Label-free proteomic analysis showed Methanosaeta was involved in DIET as reflected by the up-regulation of proteins involved in hydrogenotrophic methanogenesis. Hydrochars derived from corn straw (CH), Enteromorpha algae (EH), and poplar wood (PH), as well as activated carbon (AC), were also tested in the AD process. SH, CH, and EH obviously increased the methane production rates, which were 39%, 15%, and 20% higher than the control experiment, respectively. It was neither electrical conductivity nor the total redox property of hydrochars and AC but the abundances of surface oxygen-containing functional groups that correlated to the methane production rates.
ISSN:0013-936X
1520-5851
DOI:10.1021/acs.est.0c00112