Biochar triggers methanogenesis recovery of a severely acidified anaerobic digestion system via hydrogen-based syntrophic pathway inhibition

Improvement of Direct Interspecies Electron Transfer via Adding Conductive Materials in Anaerobic Digestion: Mechanisms, Performances, and Challenges

“…Moreover, establishing DIET by adding conductive materials significantly shortened the lag period of anaerobic digestion system even under conditions of high hydrogen partial pressure, high concentration of ammonia nitrogen, and sulfur inhibition. Wang et al (2020b) found that DIET stimulation shortened the lag time of acetate, propionate, butyrate, and valerate by 29.2, 20.5, 9.1, and 10.5%, respectively. Therefore, the promotion on syntrophic metabolism of volatile fatty acids (VFAs) may be the main reason why DIET shortens the lag period.…”

“…Furthermore, conductive carbon materials have large specific surface areas and porosities ( Figueiredo et al, 1999 ; Chen et al, 2014b ; Zhao et al, 2016a ), which play a vital role in the adsorption, fixation, and enrichment of microorganisms involved in DIET ( Qi et al, 2021 ). Meanwhile, the redox groups on the surface of conductive carbon materials, such as quinone or quinone hydrogen, may be closely related to DIET ( Wang et al, 2020b ). The possible related mechanisms are shown in Figure 2C .…”

“…Therefore, most studies speculated that performance improvement might be attributed to DIET existing in complex anaerobic digestion systems based on microorganisms already known to take part in DIET. However, the relative abundance of Geobacter in anaerobic sludge is low ( Dang et al, 2016 ; Peng et al, 2018 ; Li et al, 2020b ) or even undetectable ( Wang et al, 2020b ). In addition, several studies have demonstrated that conductive materials would enrich microorganisms with extracellular electron transfer ability, such as Desulfuromonas ( Barua et al, 2018 ), Pseudomonas ( Barua and Dhar, 2017 ), Azovibrio ( Ruiz et al, 2014 ), and Syntrophomonas ( Chen Y. et al, 2020 ), which may participate in DIET.…”

“…Conductive carbon materials not only promote metabolism of inhibitory intermediates by fixing and enriching specific microorganisms but also alleviate inhibition of toxic substances via adsorption effect ( Martins et al, 2018 ; Jung et al, 2020 ). The pH buffering capacity of conductive carbon materials also creates a favorable environment for methanogenesis ( Wang et al, 2017 , 2020b ). Simultaneously, conductive carbon materials can improve anaerobic digestion performances through other mechanisms, such as function of released ions and surface redox groups, which may affect the redox potential of anaerobic digestion systems.…”

Biochar for agronomy, animal farming, anaerobic digestion, composting, water treatment, soil remediation, construction, energy storage, and carbon sequestration: a review

“…Ambaye et al ( 2020a ) demonstrated an increase in methane generation and total volatile fatty acids elimination when fruit waste anaerobic digestion was supplemented with sludge-derived biochar. Finally, biochar may accelerate the transfer of electrons between syntrophic bacteria and methanogens, hence increasing biogas production and system stability (Wang et al 2021b , d ). These electro-trophic microbes may be successfully enhanced via the regular use of biochar; additionally, direct interspecies electron transfer may improve volatile fatty acid breakdown (Wang et al 2021b , d ).…”