Natural gas, which largely consists of methane, is one of the most important energy sources today, and is expected to be the principal intermediate fuel in a future transition to a hydrogen economy. Energy demand in Europe is growing, and much of the growth is expected to be met with natural gas, an increasing fraction of which will depend on offshore resources. The topics of are new and relevant for both scientific and economic prospects: Most of the methane from marine environments is of microbiological origin and produced in ocean margin sediments. However, the natural mechanisms of methane production, storage and transport in ocean margin sediments are insufficiently understood. Recent evidence suggests that the microorganisms producing methane could be the same or very similar to those consuming it, and that the direction of both processes might depend on biogeochemical and geological control parameters. Furthermore, it has been found that the formation of carbonate cement in hydrocarbon enriched sediments is triggered by bacteria, which has important consequences for hydrocarbon exploration. is the first European multidisciplinary project with focus on subsurface production and oxidation of methane, with the goal to develop an easily accessible database for the relevant biogeochemical and microbiological data linked to geophysical and geological data and maps. To meet the objectives, is based on the expertise of carefully selected European partners who possess, or have even developed, the required know-how and modern methodology, who have already an extensive information base on the study sites, and who include also representatives of the end-user groups.

Problems to be solved

Among the critical, general questions to address in the proposed project and to explore at selected European margin sites are:

What are the physical-chemical and biological constraints on anaerobic methane oxidation and how is the process rate controlled at the methane-sulfate transition? Is there energetic control, or do other factors such as diffusion regulate the process?

What is the population structure of the microorganisms responsible for anaerobic methane oxidation in the sea floor? Are there critical differences between methane oxidizing consortia associated with the subsurface methane-sulfate transition as compared with surficial gas hydrates or methane seeps?

What are the carbon pathways of methane production and oxidation and how is the carbon isotopic signal transferred from methane to archaea and sulfate reducers?

What is the quantitative importance of anaerobic methane oxidation for the carbon flux in ocean margin sediments? How important is it for sulfate reduction and for sulfur geochemistry? How effective is the biological methane barrier and why is the process apparently so sluggish?

How are the key processes of methane cycling in the sea floor regulated? What controls the mass balance of gross vs. net methane formation, of anaerobic oxidation, and of surficial gas accumulation?

How does the quantity and quality of buried organic matter in ocean margin sediments control the depth of the sulfate-methane interface? How does the depth and distribution of gas bubbles in sediments relate to the sulfate-methane boundary? Is the location of the upper methane barrier indicative of the long-term carbon load to ocean margin sediments?

What are the geological characteristics of methane seep areas as opposed to non-seep areas in selected margin systems, considering: occurrence of shallow gas reservoirs; fractures and faults formed as a result of neo-tectonics and glacial deformation; sediment type and accumulation rate; re-deposition due to slope instability.

How effective is anaerobic methane oxidation at sites where the methane zone penetrates up to the surface of the sea floor? Is the emitted methane still only a fraction of the ascending methane flux?

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