Attenuating Methane Emission from Paddy Fields

Rising trend of earth’s surface temperature is today a global threat to mankind. This trend is directly linked to an increasing atmospheric abundance of various greenhouse gases, like CO2, CH4 , N2O etc. emanating from man-made activities (IPCC 2007). Among these gases, CH4 is the most abundant carbon species present in the atmosphere (mixing ratio ~ 1.8 ppm). Being a highly radiatively active gas, it is a major component of the natural gas after CO2, accounting for about 20% of the global greenhouse effect (Wuebbles and Hayhoe 2002). Being highly reactive, CH4 also affects the chemistry and oxidation capacity of the atmosphere by influencing the concentrations of tropospheric ozone, hydroxyl radicals and carbon monoxide (Cicerone and Oremland 1998). Ozone formation further amplifies the methane AQ1 induced greenhouse effect by approximately 70% (Moss 1992). Global atmospheric concentration of CH4 has increased from a pre-industrial value of about 715 ppb to 1745 ppb in 1998, and to 1774 ppb in 2005 (IPCC 2007). Once emitted, CH4 remains in the atmosphere for approximately 8.4 years before removal (Dentener et al. 2003). Although atmospheric abundance of CH4 is far less than 0.5% of CO2, but on molecule to molecule basis, it is approximately 23 times more effective in absorbing infrared radiations than CO2 (IPCC 2007). Dlugokencky et al. (2003) observed that atmosphericmethane had been at a steady state of 1751 ppbv between 1999 and 2002 (Fig. 16.1). However, over the last two decades, the concentration of CH4 in the troposphere is reportedly increasing at the rate of ~ 0.7% each year and is anticipated to modify the global climate, affecting terrestrial ecosystem both functionally and structurally (Houghton et al. 1996).