B L Razdan
About 90 per cent of the Earth’s protective ozone layer resides in the stratosphere between 15km and 50km altitude. Molecular oxygen is broken down in the stratosphere by solar radiation to yield atomic oxygen, which then combines with molecular oxygen to produce ozone. Ozone is destroyed naturally through a series of catalytic cycles involving oxygen, nitrogen, hydrogen and to a lesser extent chlorine and bromine species. The abundance of stratospheric ozone is therefore chemically controlled by the stratospheric abundances of compounds containing hydrogen, nitrogen, chlorine and bromine. Increases in the abundances of methane and nitrous oxide (sources of hydrogen and nitrogen oxides respectively) thus affect the abundance and distribution of stratospheric ozone. Stratospheric ozone is also affected by the abundance of carbon dioxide (CO2), because the rates of the chemical reactions that control the abundance of ozone are temperature-dependent, and the abundance of CO2 plays a key role in determining the temperature structure of the stratosphere. While methane is a more potent greenhouse gas than CO2, there is over 200 times more CO@ in the atmosphere. Hence the amount of warming methane contributes is 28% of the warming caused by CO2.
A United Nations report has identified the worlds rapidly growing herds of cattle as the greatest threat to the climate, forests and wildlife. Livestock are responsible for 18% of the greenhouse gases that cause global warming, more than cars, planes and all other forms of transport put together. Burning fuel to produce fertilizer to grow feed to produce and to transport it – and clearing vegetation for grazing – produces 9% of all emissions of CO2, the most common greenhouse gas. And their wind and manure emit more than one third of emissions of another, methane, which warms the world 20 times faster than CO2.
Livestock belch out or release methane gas as they digest their food. And a methane molecule released into the atmosphere, has a 25 times greater capacity for trapping heat than a carbon dioxide molecule. Rice, meat, dairy products and fish are associated with high methane emissions while wheat, vegetables and fruits contribute to an oxide of nitrogen – another greenhouse gas that has an even greater heat trapping capacity than methane. Bananas had the least global warming potential, according to the research analysis inasmuch as much of the emissions associated with bananas emerge from their transportation from plantations to retail outlets.
In early 1990s, the Indian scientists were caught by surprise when the US researchers had suggested that India’s paddy fields were producing a large amount of methane unmindful of the fact that the livestock industry had a much bigger impact on the environment. This prompted an indigenous research in the subject that showed that the US claims were far exaggerated. The research also led to the assessment of the greenhouse gas emissions during each stage of the lifecycle of various food items from the farm to the dining table viz. production, processing and cooking, so to say, to generate a comparative chart.
The research designed to generate raw data about the global warming potential of Indian food items has determined the Global Warming Potential in gram carbon dioxide per kg thus: Apple (357), Banana (98), Basmati rice (859), Chapati (250), Dosa (729), Fish (756), Idli (682), Parantha (261), Potato (132), Poultry meat (801), Milk (766), Mutton (9149), Rice (712).
The data thrown up as above clearly shows that a kilogram of mutton has a global warming potential 12 times higher than a kilogram of fish. The global warming potential of poultry meat – chicken or duck – is only slightly higher than that of fish. It also makes it abundantly clear that vegetarians are far more environment-friendly than the non- vegetarians. For the sake of the planet earth and for their own sake, the latter can do their bit by eating a little less meat – or better still, shift over to “mock meats” or vegetarian meats, now available in a large number of Washington area restaurants, where the wizardry and skill of counterfeiting meat has become a sophisticated art.
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