WASHINGTON: Cow dung can generate enough power to meet three per cent of North America's entire energy needs and cut down greenhouse gas emissions. Cow dung, left to decompose naturally, emits two particularly potent greenhouse gas emissions (GHGs) - nitrous oxide and methane. Nitrous oxide warms the atmosphere 310 times more than carbon dioxide, methane does so 21 times more, according to the Intergovernmental Panel on Climate Change (IPCC). The study creates two hypothetical scenarios and quantifies them to compare energy savings and GHG reducing benefits. The first is "business as usual" with coal burnt for energy and with manure left to decompose naturally. The second is one where manure is anaerobically digested to create biogas and then burnt to offset coal. Through anaerobic digestion, similar to the process by which compost is created, manure can be turned into energy-rich biogas, which standard micro-turbines can use to produce electricity. Hundreds of millions of livestock inhabiting the US could produce approximately 100 billion KW hours of electricity, enough to power millions of homes and offices. And, as manure left to decompose naturally has a very damaging effect on the environment, this new waste management system has a net potential GHG emissions reduction of 99 million metric tonnes, wiping out approximately four per cent of the country's GHG emissions from power production. The burning of biogas would lead to the emission of some carbon dioxide but the output from biogas-burning plants would be less than that from, for example, coal. Michael E. Webber and Amanda D. Cuellar from the University of Texas at Austin, co-authors of the paper wrote that in light of the criticism levelled against bio-fuels, biogas production from manure has the less-controversial benefit of reusing an existing waste source and has the potential to improve the environment. These findings were published Thursday in the Institute of Physics' Environmental Research Letters.