Climate Geoengineering and Cow Dung Smog

                                                    The Taj Mahal enveloped in a cow dung smog.

India recently banned the burning of cow dung near the Taj Mahal, in an attempt to reduce the amount of smog in the air around the famous architectural gem.  This might surprise people who think that smog is only a product of factory emissions and and car exhausts, but smog produced by burning cow dung is a severe problem in India.

I first encountered cow dung smog when I was trekking in the Himalayas of Nepal some years ago.  The trekking routes used by western trekkers usually follow traditional foot paths used by Nepalis as they travelled between villages in the southern Himalayas.  The rugged and steep trekking paths go high into the mountains to cross mountain passes between small Nepali villages.  In many parts of Nepal the trails are still the only way to reach many small, isolated villages built in the valley bottoms, or perched on small areas of flat ground up in the mountains.    

As we trekked into these remote Nepali villages, miles from any automobiles or industrial activity, we encountered miasmas of smog.  How, we wondered, could there be smog without cars? We observed many small fires were burning and emitting a stanky smoke throughout the village---some of the fires were inside huts and some outside in the fields----and dried cow dung was the fuel being burned.  

Cows are considered sacred by Hindus, and may not killed or eaten.   However, it is less well known that cows are nonetheless a key part of the subsistence rural economy in Nepal and India because cow dung from the sacred cows is an important fuel.  The dung is gathered, dried, and burned for heat and cooking along with wood gathered from mountains forests.   In densely populated India the use cow dung for fuel is critical because, for the most part, there are no remaining forests from which peasants can gather firewood.

It is estimated that about a billion people around the world use cow dung as a source of fuel.   In addition to Nepal and India, cow dung is important in Egypt and parts of the rest of Africa, China and other areas in southeast Asia, Mongolia, Pakistan, Bangladesh, Syria and Turkey.   And as the population of these regions increase, so does the population of cows that the economy depends on for fuel.

Cows are ruminants and live on grass.  Although huge amounts of CO2 are given off when cow dung is burned, this CO2 would've been released into the atmosphere anyway because grass dies and decays at the end of the summer.  But Cows and cow dung are still a significant source of greenhouse gases because  cows themselves release large quantities of methane and ammonia, and still more methane and ammonia is released when cow dung is burned.    Because methane is such a powerful Greenhouse gas (by some estimates CH4 is 23 times more powerful then CO2 at trapping heat), cows are thought to be responsible for about 18% of all global warming.

So what can the CO2 Antarctic Pumpdown geoengineering proposal and other geoengineering proposals doe about cows and cow dung smog and methane in the atmosphere?  Just about nothing.  Once methane gets into the atmosphere it is almost chemically inert---by some estimates any methane that gets into the atmosphere will stay there for almost a thousand years, with the greenhouse effect due to methane gradually increasing as the CH4 concentration in the atmosphere builds up.

Today's cow dung smog is tomorrow's greenhouse warming.