From the epa so yeah not sure how you got the 10% idea Methane (CH4) is the second most prevalent greenhouse gas emitted in the United States from human activities. In 2013, CH4 accounted for about 10% of all U.S. greenhouse gas emissions from human activities. Methane is emitted by natural sources such as wetlands, as well as human activities such as leakage from natural gas systems and the raising of livestock. Natural processes in soil and chemical reactions in the atmosphere help remove CH4 from the atmosphere. Methane's lifetime in the atmosphere is much shorter than carbon dioxide (CO2), but CH4 is more efficient at trapping radiation than CO2. Pound for pound, the comparative impact of CH4 on climate change is 25 times greater than CO2 over a 100-year period. Globally, over 60% of total CH4 emissions come from human activities.  Methane is emitted from industry, agriculture, and waste management activities, described below.