WSJ Video: Watch how methane is measured : Gassy Sheep Add to Global Warming
Did you hear that cow farts are causing global warming?
Contrary to popular belief, most of the methane emissions from cows and other livestock aren’t from flatulence or farts. They’re from burping. About 98 per cent of the methane from a cow is emitted through its mouth. (source: Kebreab, Journal of Animal Science.
The average grain-fed dairy cow belches out about 500 litres of methane each day, compared to about 600-700 litres a day per grass-fed cow, due to their unique enteric fermentation digestive process. (source: Ermias Kebreab of the National Centre for Livestock and the Environment).
In total, livestock’s total gas emissions include 37% of all methane (20 times more powerful than CO2) and 65% of all nitrous oxide (296 times).
Yes it’s much funnier to talk about farting than burping/belching. It certainly raises more eyebrows, which explains why many of the headlines on cattle methane go for the “farting to blame for global warming” angle instead, despite its inaccuracy.
But whether it’s farting or burping, it’s given plenty of ammunition for global warming skeptics to make light of global warming, and the research & policies that are proposed to address animal agriculture’s impact.
The statistics below will help dispel the inevitable joke/comment on our gassy footprint. In summary, we have a LOT of livestock, which have HUGE diets!
You: Just how many livestock are you talking about?
- In 2007, at any given time, there were approximately 1.3 billion cattle, 1 billion sheep, 1 billion pigs, 800 million goats and 17 billion chicken (UN FAO). This means – one cattle for every five people, one sheep for every six, one goat for every eight, and 2.5 chickens for every person.
- 10 billion animals are raised and slaughtered each year in the USA (30 animals for each American)
You: Gee that’s a lot of livestock. How much do they eat?
- Each day, a cow eats about 20 pounds of grain, 40 – 60 pounds of ensilage, 30 pounds of hay and drinks about 15 – 25 gallons of water
You: Impressive. Since they eat so much… they must poop a lot right?
- Animals raised for food produce 1.4 billion metric tons of manure, which is 130 times more excrement than the entire human population put together, for a total of 87,000 pounds per second.
When one looks at the number of animals which are eaten, and the amount of crops and energy that are required to feed them, it becomes increasingly clear that we must define the problem as rising meat consumption, not the cows themselves. According to the UN FAO, annual global meat production is projected to more than double from 229 million tons in 2000 to 465 million tons in 2050.
Whenever one discusses cow farts or burps (which I suppose is an interesting conversation starter), it’s also important to understand that methane emissions from livestock are only one part of the “meat footprint”. The emissions from the meat production process includes many other steps which generates high levels CO2.
Some of the ways which animal agriculture industry generates its CO2 emissions include: the clearing forests for cattle grazing or planting feed (Brazilian Amazon especially), slaughtering livestock in factories, and transporting, storing and packaging the meat. More on these other greenhouse gas producing processes another time.
For now, please don’t let the global warming skeptics keep you from holding in farts (it’s bad for you) or keep you from enjoying beans.
Correction: A previous version cited that the average dairy cow belches out about 100 to 200 liters of methane each day, according to Michael Abberton, a scientist at the UK-based Institute of Grassland and Environmental Research. Guess you can average it out.)
