1. Zhen,Y.,Sara, K.,Tianran,S.,Ruben, K. and Andreas,K.
Effect of Redox Activity and Conductivity of Biochar Particles on Methane Emission and Fe(III) Reduction in Anoxic Paddy Soil
Zhen,Y.,Sara, K.,Tianran,S.,Ruben, K. and Andreas,K.

2. Electron Transfer by Biochar
Redox activity electrons accepted and donated by functional groups of biochar
Conductivity a rapid electron transfer by carbon matrice in biochar
Arrow thickness indicates
e- transfer kinetics
Pathway °C
Pathway °C
Geoconductor mechanism
Geobattery mechanism
External electron acceptors
Pathway °C
External electron donors e-
e- flow
(Klüpfel, L. et al., 2014) 2
(Sun, T.R. et al., 2017)

3. Biochar as Electron Shuttle
Biochar functions as an electron shuttle (e- transfer via functional groups of biochar) transferring electrons between microbes and Fe(III) minerals
Biochar addition influences the rate and extent of microbial Fe(III) reduction
ferrihydrite
hematite
Fe(III) mineral
Shewanella oneidensis MR-1 e- O OH
(Kappler. A et al., 2014 ; Xu. S. et al., 2017) 3

4. Competition for Electron Donor between Microbial Fe(III) Reduction and Methanogenesis
Oxic
Anoxic
acetate
Fe(III) reduction
methanogenesis
FeIII
FeII e-
CO2 CH4
Fe(III)-reducing bacteria
methanogenic archaea
CO2 4

5. Competition for Electron Donor between Microbial Fe(III) Reduction and Methanogenesis
Oxic
Anoxic
acetate
Fe(III) reduction
methanogenesis
FeIII
FeII e-
CO2 CH4
Fe(III)-reducing bacteria
methanogenic archaea
CO2 5

6. Biochar addition stimulate microbial Fe(III) reduction (in paddy soil)
Competition for Electron Donor between Microbial Fe(III) Reduction and Methanogenesis
Biochar addition stimulate microbial Fe(III) reduction (in paddy soil)
Oxic
Anoxic
acetate
Fe(III) reduction
methanogenesis
Biochar
Redox functional groups and conductive carbon matrices in biochar
FeIII
FeII e-
CO2 CH4
Fe(III)-reducing bacteria
methanogenic archaea
CO2 6

7. Competition for Electron Donor between Microbial Fe(III) Reduction and Methanogenesis
Biochar:Fe(III) mineral ratios control microbial Fe(III) reduction by functioning as electron shuttle, conductor and capacitor (in Shewanella MR-1 suspension)
Oxic
Anoxic
acetate
Fe(III) reduction
methanogenesis
Biochar
Redox functional groups and conductive carbon matrices in biochar
FeIII
FeII e-
CO2 CH4
Fe(III)-reducing bacteria
methanogenic archaea
CO2
(Submited) 6

8. Competition for Electron Donor between Microbial Fe(III) Reduction and Methanogenesis
Biochar addition was shown to inhibit or stimulate methanogenesis
with partially controdictory results in the literatures
Oxic
Anoxic
acetate
Fe(III) reduction
methanogenesis
Biochar
Redox functional groups and conductive carbon matrices in biochar
FeIII
FeII e-
CO2 CH4
Fe(III)-reducing bacteria
methanogenic archaea
CO2 7

9. Research Questions
Do biochar particle size and biochar:Fe(III) mineral ratios influence the competition between microbial Fe(III) reduction and methanogenesis?
Is this associated with changes in the microbial community composition? 8

10. Results and Conclusions
Biochar particle sizes and biochar:Fe(III) mineral ratios influence microbial communities and electron transfer pathways
This controls the competiton between microbial Fe(III) reduction and methanogenesis in anoxic paddy soil
Welcome to poster board 429 in Session 12f, 17: :30 ! 9

11. Acknowledgements Geomicrobiology group (Tübingen)
Center for Applied Geosciences Geomicrobiology
Acknowledgements
Geomicrobiology group (Tübingen)
Microbial Ecology group (Tübingen)
D. Straub
(University of Tübingen, Geoscience)
J. G. Usack
(University of Tübingen, Environmental Biotechnology) 10