Accelerated methanogenesis from aliphatic and aromatic hydrocarbons under iron- and sulfate-reducing conditions.
The impact of four electron acceptors on hydrocarbon-induced methanogenesis was studied. Methanogenesis from residual hydrocarbons may enhance the exploitation of oil reservoirs and may improve bioremediation. The conditions to drive the rate-limiting first hydrocarbon-oxidizing steps for the conversion of hydrocarbons into methanogenic substrates are crucial. Thus, the electron acceptors ferrihydrite, manganese dioxide, nitrate or sulfate were added to sediment microcosms acquired from two brackish water locations. Hexadecane, ethylbenzene or 1-(13)C-naphthalene were used as model hydrocarbons. Methane was released most rapidly from incubations amended with ferrihydrite and hexadecane. Ferrihydrite enhanced only hexadecane-dependent methanogenesis. The rates of methanogenesis were negatively affected by sulfate and nitrate at concentrations of more than 5 and 1 mM, respectively. Metal-reducing Geobacteraceae and potential sulfate reducers as well as Methanosarcina were present in situ and in vitro. Ferrihydrite addition triggered the growth of Methanosarcina-related methanogens. Additionally, methane was removed concomitantly by anaerobic methanotrophy. ANME-1 and -2 methyl coenzyme M reductase genes were detected, indicating anaerobic methanotrophy as an accompanying process [Correction added 16 December after online publication: 'methyl coenzyme A' changed to 'methyl coenzyme M' in this sentence]. The experiments presented here demonstrate the feasibility of enhancing methanogenic alkane degradation by ferrihydrite or sulfate addition in different geological settings.
Bundesanstalt für Geowissenschaften und Rohstoffe, Hannover, Germany. michael@siegert.org
Michael
M
Siegert
Danuta
D
Cichocka
Steffi
S
Herrmann
Friederike
F
Gründger
Stefan
S
Feisthauer
Hans-Hermann
HH
Richnow
Dirk
D
Springael
Martin
M
Krüger
D000693:Anaerobiosis; D001530:Belgium; D001673:Biodegradation, Environmental; D002245:Carbon Dioxide / Q000378:metabolism; D005290:Ferric Compounds / Q000378:metabolism; D045302:Geobacter / Q000235:genetics / Q000378:metabolism*; D019015:Geologic Sediments / Q000737:chemistry / Q000382:microbiology; D006839:Hydrocarbons, Acyclic / Q000378:metabolism*; D006841:Hydrocarbons, Aromatic / Q000378:metabolism*; D007501:Iron / Q000378:metabolism; D017895:Manganese Compounds / Q000378:metabolism; D008697:Methane / Q000378:metabolism*; D017020:Methanosarcina / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009566:Nitrates / Q000378:metabolism; D010084:Oxidation-Reduction; D010087:Oxides / Q000378:metabolism; D013431:Sulfates / Q000378:metabolism; D013997:Time Factors
D005290:Ferric Compounds; D006839:Hydrocarbons, Acyclic; D006841:Hydrocarbons, Aromatic; D017895:Manganese Compounds; D009566:Nitrates; D010087:Oxides; D013431:Sulfates; D002245:Carbon Dioxide; C092844:ferric oxyhydroxide; D007501:Iron; D008697:Methane; C016552:manganese dioxide