Page 256 - Microbial methane cycling in a warming world From biosphere to atmosphere Michiel H in t Zandt

Chapter 11. Integration and outlook
2020, with most significant drops in advanced economies like the United States (-25%) and the European Union (-20%) (IEA 2020a). This is potentially good news for GHG emissions, since the coal industry provides the largest anthropogenic source of CO2. GHG emissions from coal were 14 Gt in 2016, which equals 40% of the total fossil fuel emissions and nearly 25% of total global greenhouse gas emissions (Hood 2018; IEA 2018, 2019a). In addition, direct coal burning leads to the emission of sulfurous and nitrogenous compounds (SOx, NOx), heavy metals, and particulate pollution that contaminates global ecosystems, including forests, grasslands, and wetlands (Hendryx, Zullig and Luo 2020).
Methane is also biologically produced from coal, and it could provide a cleaner energy source in terms of secondary pollution. However, in Chapter 4, we found that coal biomethanation is difficult to achieve in harder, sub-bituminous coal types. Our observations are supported by several other studies on strategies for coal methanogenesis (Moore 2012; Fuertez et al. 2017). Even though direct methanogenesis has been described from coal through methoxydotrophic methanogenesis, the conditions required for this pathway are generally not met. These conditions include high temperatures of around 60°C for Methermicoccus shengliensis and ample supplies of methoxylated aromatic compounds (Cheng et al. 2007; Mayumi et al. 2016; Kurth, Op den Camp and Welte 2020).
Within the global picture, CH4 from coal still results in fossil carbon emissions into the atmosphere that contribute to the enhanced greenhouse effect. Therefore, research towards CH4 production from coal should not be a priority. However, a clear understanding of the potential for coalbed methanogenesis from different coal types and locations can provide valuable insights into the reduction of coalbed fugitive CH4 emissions into the atmosphere. An estimated nine percent of global CH4 emissions originates from coal wells, which further stresses the urgency of reducing these emissions (EPA 2020).
Interactions between microbes and infrastructure provide hints for the protection of steel constructions
Several peat ecosystems include manmade structures for landscape stabilization. Interestingly, there is a strong interaction between manmade structures and the in situ microbial communities. In Chapter 3, we studied microbially inhabited deposit layers that were involved in corrosion
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