Hey Mr. Green,

I’ve heard that belching and farting from cattle and other livestock is a major cause of global warming. What’s your take?

—Tim, in Springfield, Missouri

Some adults seem to get more excited by the gaseous by-products of digestion than 10-year-old boys. Unlike the lads, however, they are not amused by them.

The total greenhouse gas emissions from the digestive processes of livestock—what is politely called “enteric fermentation”—are 164.5 million metric tons, mostly from dairy and beef cattle, according to EPA estimates.  Add emissions from manure to this total and you get the equivalent of 243.2 million metric tons of carbon dioxide, or 3.6 percent of all U.S. greenhouse gas emissions. So cattle belching and farting per se amount to 2.5 percent of our total greenhouse gas.

You can reduce these emissions by cutting back on your meat consumption, or going vegetarian or vegan, but you shouldn’t get all complacent and self-righteous about such abstinence. After all, electric power plants and transportation account for a lot more greenhouse gas than livestock, accounting for 31 percent and 27 percent of it respectively.  And just to put things in perspective, the population of the American bison, an intrepid enteric fermenter who can match a bovine belch for belch, numbered between 30 and 60 million before white colonialists burst upon the scene and blasted them nigh unto extinction. Today’s beef herd of 88 million doesn’t seem outrageously large in comparison.  I do suspect that at some future time, if we’re not vaporized thanks to a nuclear hacker, that the vast prairies of the United States will restored, and the buffalo population will return to its ancient levels, becoming a reliable source of protein and wonder.—Bob Schildgen