Generation of methane from paddy fields and cattle in India, and its reduction at source

Methane (CH4) is a saturated organic gas. About 500 Tg yr(-1) methane is generated globally. It is evident that 70% of the total emission have anthropogenic sources. The paddy fields contribute a significant portion of the total methane generated. About 20% of the total methane is generated from the paddy fields. In India, methane efflux rate is negative to 49 mg m(-2) hr(-1). The mean CH4 flux from Indian paddy fields is calculated to be 4.0 Tg yr(-1). Livestock, and in particular ruminants are one of the important sources of methane emission on a global scale. There are two sources of methane emission from live stock: (1) from digestive process of ruminants. (2) from animal wastes. The estimated value of methane emission from digestive process of ruminants in India accounts for 6.47 Tg yr(-1), and animal wastes accounts for 1.60 Tg yr(-1). Total generation of methane from animals in India is about 1.0 Tg yr(-1). In paddy fields the key of controlling methane emission lies in the control of irrigation water. The methane emission can be decreased drastically if the field is under dry conditions for a few days at the end of tillering. In the case of livestock, reduction of methane emission can be done by (1) increasing the intake of the animal (2) modifying the composition of the diet, (3) eliminating protozoa in rumen, (4) improving fibre digestion efficiency and (5) inhibiting activity of methanogenic bacteria. Copyright (C) 1996 Elsevier Science Ltd.