Rice Cultivation
The cultivation of rice is an entirely man-made activity and is the largest artificial source of methane and considered to be one of the primary culprits in rising methane levels in the atmosphere. Production of rice has more than doubled in the past 60 years and rice cultivation is estimated to produce between 50 and 100 million tons of methane per year. As the human population grows, the demand for rice production increases leading to even an even greater release of methane into the atmosphere.
Grazing Animals
On a global scale, grazing animals, such as cows and sheep, emit around 80 million tons of methane per year. This methane is generated during digestion in a process known as enteric fermentation. During this process, methane is produced in a specialized stomach called the rumen. The rumen aids in the digestion of foods like grass and hard grains. The gas is emitted through belching and flatulence. As the human population grows so does the need for more livestock thus increasing the amount of methane released, over time.
Termites
Termites release methane in a manner similar to grazing animals. The release of methane due to the digestive process of termites is estimated to be between 2 and 22 million tons per year. Termites are a natural source of methane emissions however, human activities such as deforestation, farming and other agricultural pursuits contributes to exploding populations of termites. The increased population in turn increases the production of methane by the insects.
Landfills
Decomposing organic waste, such as uneaten meat and vegetaables and human waste products produce methane over time. Due to the amount of slowly decaying waste present, landfills act as sources of methane production for years beyond their closure. Methane emissions from landfills, on a global scale, are estimated to be between 30 and 70 million tons annually and growing.