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The growth of agriculture is
also leading to increasing
emissions of methane. In the last few decades, there has been a
substantial
increase in livestock numbers - cattle, in particular - much of which
has been
made possible by the conversion of tropical forests to pasture. Cattle
emit
large amounts of methane and the destruction of forests for
cattle-raising is
therefore leading to increased emissions of two of the most important
greenhouse gases.
Worldwide, the emissions of methane emitted by livestock amounts to some 70 million tonnes. With modern methods of production, cattle are increasingly fed on a high-protein diet - especially when fattened in feedlots. Such cattle emit considerably more methane gas than grass-fed cattle. Even the fertilization of grasslands with nitrogen fertilizers can both decrease methane uptake and increase nitrous oxide production, which thereby increases atmospheric concentrations of both these gases.
Worldwide, the emissions of methane emitted by livestock amounts to some 70 million tonnes. With modern methods of production, cattle are increasingly fed on a high-protein diet - especially when fattened in feedlots. Such cattle emit considerably more methane gas than grass-fed cattle. Even the fertilization of grasslands with nitrogen fertilizers can both decrease methane uptake and increase nitrous oxide production, which thereby increases atmospheric concentrations of both these gases.
The expansion of rice paddies has also seriously increased methane emissions. Rain-fed rice produces far less methane than inundated rice fertilized with nitrogen fertilizer. Once again, the modernization of agriculture increases methane gas emissions as well as nitrogen emissions.[i]
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Atmospheric methane is an integral component of the greenhouse effect, second only to CO2 as a contributor to the total anthropogenic GHG warming in the atmosphere. The overall contribution of CH4 to global warming is 21 times more effective at trapping heat in the atmosphere with respect to CO2 (IPCC, 1996). From the pre-industrial times to the present, the concentration of CH4 in the atmosphere has increased 151 times (IPCC, 2001a). The main factors contributing to this increase are: proliferation in activities related to exhaustive mining of coal for energy use; emissions due to handling of oil and natural gas systems; dependence on products derived from livestock; waste management; increased production of rice to meet the demand of the growing population; on-site burning of crop residue for preparing the fields for the next cropping; cycle management of solid waste; and waste water from the domestic and the industrial sectors.[ii] |
| Methane emissions in India in 1994 |
The total national CH4 emission
in 1994 from the
above-mentioned sources was 18,083 Gg. The agriculture sector dominated
with 78
per cent of the total national CH4 emissions, within which emissions
due to
enteric fermentation (8,972 Gg) and rice cultivation (4,090 Gg) were
the
highest. Of such emissions 16 per cent came from the energy systems
comprising
emissions due to biomass burning, coal mining and handling and flaring
of
natural gas systems. Waste disposal activities contributed about 6 per
cent of
the total CH4. Methane emissions from the LULUCF sector were minor in
nature,
mainly due to the burning of biomass in forests. Similarly, the
contribution of
the industrial process sector to the total national CH4 emissions is
miniscule
in comparison with other sources and is only around 2 Gg.[iii]
[i]
How
to feed people under a regime of climate change by Edward
Goldsmith. Edward
Goldsmith, October 2003
[ii][iii]
India's
Initial National Communication to the United Nations Framework
Convention on
Climate Change, Ministry of Environment and Forests,
Government of India,
2004
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