A just-published analysis of data received from a satellite in 2004 has shown that at least during that year, livestock in the U.S. emitted more methane into the atmosphere than did the oil and gas industry. In their article published in Journal of Geophysical Research: Atmospheres, a team of researchers from Harvard University, California Institute of Technology and the University of California studying the data note that such emissions were far higher than was reported by the U.S. Environmental Protection Agency (EPA).
Specifically, the researchers found satellite data showed livestock emitted 13 million tons of methane over the summer in 2004 (the EPA reported 9.7 million tons). They found the satellite data also showed that the combined emissions of the oil and gas industry amounted to 7 million tons (the EPA reported 9.9 million tons).
Unfortunately the sensor on the satellite was unable to show methane amounts after 2004, thus more data is not available. That will, however, change soon as a new satellite with sophisticated atmospheric gas monitoring sensors aboard is set to launch next year. More information on the role that methane plays in changing our climate can be found here.
There's also the problems of leaking methane from reticulation systems, pretty much ignored until people started pounding the pavement with sensors.
The grid size of this satellite sensor was huge and is afaik dependant on the accuracy of ground observations for calibration.From reading about it it seems they use a model for mixing of gases to figure out how to plot the concentrations.
What I wonder is how the data is different for, say, me opening a valve on a tank of gas in the middle of a field vs a couple of hundred cows in that field.