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Wetland soils, however, are often sources of atmospheric methane rather than sinks because the water table is much higher, and the methane can be diffused fairly easily into the air without having to compete with the soil's methanotrophs. [73] Methanotrophic bacteria also occur in the underwater sediments.
Hydrogen, being the lightest existing gas (7% the density of air, 0.08988 g/L at STP), seems to be the most appropriate gas for lifting.It can be easily produced in large quantities, for example with the water-gas shift reaction or electrolysis, but hydrogen has several disadvantages:
Methane has a limited atmospheric lifetime, about 10 years, due to substantial methane sinks. The primary methane sink is atmospheric oxidation, from hydroxyl radicals (~90% of the total sink) and chlorine radicals (0-5% of the total sink). The rest is consumed by methanotrophs and other methane-oxidizing bacteria and archaea in soils (~5%). [5]
Scientists are also worried about the rapid rise in atmospheric levels of methane, a shorter-lived but more potent heat-trapping gas. Both jumped 5.5% over the past decade.
The heat needed for the reaction can also be GHG emission free, e.g. from concentrated sunlight, renewable electricity, or burning some of the produced hydrogen. If the methane is from biogas then the process can be a carbon sink. Temperatures in excess of 1200 °C are required to break the bonds of methane to produce hydrogen gas and solid carbon.
Global emissions of methane from existing gas infrastructure may be up to five times higher than had been believed, a new study has found. Existing measures to burn off the powerful greenhouse gas ...
Additionally, if the water table is lowered significantly enough, then the wetland can actually be transformed from a source of methane into a sink that consumes methane. Finally, the actual composition of the original wetland changes how the surrounding environment is affected by the draining and human development.
The most clearly identified rise in atmospheric methane as a result of human activity occurred in the 1700s during the industrial revolution. During the 20th century—mainly because of the use of fossil fuels—concentration of methane in the atmosphere increased, then stabilized briefly in the 1990s, [56] only to begin to increase again in ...