Page 33 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

Carboniferous Period (359-299 million years ago) and comprise an important carbon sink that has resulted in the removal of large amounts of CO2 from the atmosphere (Richards 2013). Currently coal mining has a big environmental impact and is estimated to result in emissions of 10-15 Pg CO2 from coal burning (2002-2018) and 26-50 Tg of fugitive CH4 emissions through mining activities (2003-2012) per year (Saunois et al. 2016; IEA 2019a). Coalbed methane is produced through both biological and thermogenic processes, and escapes from both active and abandoned coal mines. On a global scale, these emissions amount to 11% of the total yearly anthropogenic CH4 budget (Saunois et al. 2016). The exploitation of coalbed CH4 could thus strongly reduce fugitive coalbed CH4 emissions.
Coalbed CH4 exploitation can also provide an environmentally more sustainable alternative to direct coal burning (Fakoussa and Hofrichter 1999; Al-Jubori et al. 2009; Kinnon et al. 2010). Direct coal burning leads to environmental pollution in the form of heavy metals and sulfur compounds (Querol, Fernández-Turiel and López-Soler 1995). However, in many instances, coalbed CH4 harvesting is not profitable due to unfeasibly low CH4 production rates and barriers to a selling market (Moore 2012). As a result, many active CH4-producing coal systems are neglected and thus remain sources of CH4. Microbial process-based studies can help to successfully optimize coalbed CH4 production. Even though coalbed CH4 remains a fossil carbon fuel with a large carbon footprint, it can nevertheless provide a more sustainable step on the transition to climate neutrality.
Peatlands have a central role in the global carbon cycle
On shorter timescales, peatlands play an active and important role in the global carbon budget by sequestering atmospheric CO2. They form when decomposition rates are lower than primary production rates (Limpens et al. 2008). Peatlands act as major C reservoirs by storing up to one third of the Earth’s terrestrial C stocks in the form of dead organic matter (Gorham 1991; Treat et al. 2019). Although they have been developing since the evolution of wetland plants, most of present-day peatlands have originated in the Holocene Epoch (11.7 thousand years ago till now) (Gajewski et al. 2001; Treat et al. 2019). Their slow mineralization rates and constant carbon sequestration make peatlands important active C sinks in the global carbon budget.
About one-third of the Holocene peatlands are currently buried in marine sediments (Törnqvist and Hijma 2012). Due to rapid warming at the start of the Holocene, the ice sheets
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