FROZEN HEAT | Volume 1
Teragrammes Methane mass released per year
Primary sources of methane release
231
100
Minimum Maximum
Ruminant emissions
Biomass burning
Wetlands
90
80
Landfills
70
Oil andGas (Burned as fuel)
Rice Paddies
60
Coal (Burned as fuel)
50
40
Termite emissions
30
Geological sources
Wild animal emissions
20
Wildfires
Oceans
Gas hydrates
10
0
Source: IPCC (2007)
Figure 2.2: Primary methane emissions to the atmosphere per year. Methane emissions due to human-related activities, shown to the right of the volcano, account for approximately 70 per cent of the total emissions (Reeburgh 2007; Colwell and Ussler III 2010). Gas Hydrates are currently estimated to contribute about 5 Tg (Tg = 10 12 grammes) of methane (3.5 Tg carbon) per year to the atmosphere (IPCC, 2007). Emission rates for gas hydrates are highly speculative, however, and may overestimate the atmospheric methane contribution by not fully accounting for methane consumed by microbes in the sediment and water column (Fig. 2.3). Additional research will be required to constrain the methane flux from gas hydrates that reaches the atmosphere.
A GLOBAL OUTLOOK ON METHANE GAS HYDRATES 35
Made with FlippingBook