In this study the release of methane to the atmosphere by the USSR is estimated. This paper includes estimate of the methane fluxes from USSR wetlands, fossil fuel mining and cattle, and also their possible geographical distributions. It is shown that the USSR methane sources are 11% of the global value of 540 Tg. Using a simple model of the transformation of soil organic matter, it is estimated that the maximum methane flux from USSR wetlands is 11 Tg/yr. Thus the USSR contributes less than 10-13% of the world's methane flux from wetlands. The estimates of the maximum methane fluxes from coal mining, oil mining and gas mining (including transportation and storage) are 18, 7 and 11 Tg/yr, respectively. Thus the USSR contributes up to 43% of the global fossil fuel source of methane. The upper limit of the methane flux from USSR cattle is 12 Tg which is 15% of the global cattle methane source. It is concluded that geographically there are two maximum values of methane flux from the USSR which are formed by inputs from the different methane sources. The first methane flux maximum is located in the West Siberian Plain and is formed dominantly by gas and oil mining. The second methane flux maximum is located in the Ukraine and neighboring regions, and is formed by coal mining, wetlands and cattle.
