Page 255 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

and tropical climates (Lottes and Ziegler 1994). They thus play an important role in global GHG source and sink dynamics.
As seen in Chapter 5, peat sediments can provide important long-term carbon sinks. The conversion of freshwater to marine ecosystems, as was observed for the North Sea deposits, seems to stabilize the organic carbon fractions that are stored. In the future, such organic carbon sediments can be abiotically converted into coal deposits, and, thus, be further protected against biological conversions. Coal can be seen as the ultimate long-term peat storage, and although coal is largely resistant to microbial degradation, it provides an important energy source for humanity.
Currently, the potential contributions of marine buried peat sediments to the global GHG budget are unknown. In Chapter 5, we characterized the microbial community and quantified its potential contribution to GHG emission. We found that, under in situ conditions, the GHG production potential is negligible, indicating that marine peat sediments will be important long- term carbon sinks.
Further understanding the conversion of freshwater peatlands into marine ecosystems can be used as a tool to prevent the microbial degradation of peat organic matter in coastal wetlands. Overall, coastal wetlands are sources of CH4 and N2O, but sinks of CO2 (Tan et al. 2020). Marine influences show the promising potential to suppress the production of both CH4 and CO2, but the contribution of N2O can increase (Doroski, Helton and Vadas 2019). There is a clear link with freshwater thermokarst lakes, which are potentially smaller CH4 sources when they transition into thermokarst lagoons. Therefore, future efforts should target the quantification of these changes on the global GHG budget. These studies should include field data of microbial diversity shifts, the GHG fluxes of thermokarst lakes that are transitioning into thermokarst lagoons, and laboratory-based studies on important tipping points of this transition regarding community and GHG production shifts.
Coal is an abundant energy source of the Earth and a potential source of methane
The fossil fuel coal has been the major source for electricity generation worldwide up to 2016, and it still provides around 25% of the power produced today (IEA 2019b, 2020a). Due to both the corona crisis and energy transitions, the global coal demand is expected to fall with 8% in
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