Cows, Farts and Global Warming
In discussions of global warming we always hear about greenhouse gas emissions and fossil fuels adding
CO2 to our atmosphere. But there is much more to the story. One interesting part is methane and the
flatulence of cows.
The flatulence of cows is only a small portion of
cows' methane release. Cows also burp methane.
CH4 is the symbol for methane.
CO2 is the symbol for carbon dioxide
Greenhouse gases (GHG) are gases that emit or reflect infrared radiation. Infrared radiation is light that
we can’t see because it is just beyond the long, harmless, visible red light waves that we can see.
However, we can feel infrared radiation as heat. Gases that absorb or emit infrared radiation keep the
earth warm.
These are the most abundant greenhouse gases in Earth’s atmosphere in order from most prevalent to
least.
• Water vapor (H2O)
• Carbon dioxide (CO2)
• Methane (CH4)
• Nitrous oxide (N2O)
• Ozone (O3)
• Chlorofluorocarbons (CFCs)
Even though water vapor is the most abundant greenhouse gas, our human behavior doesn’t have much
affect on the amount of water vapor there is in our atmosphere. So greenhouse gases that people have
helped to create or that we can have an impact on lowering are the gasses that scientist calculate and call
anthropogenic (resulting from the influence of human beings on nature). We have the ability to reduce
these anthropogenic greenhouse gases.
1. Now let’s include water vapor in these calculations. The direct contribution to the greenhouse
affect of water vapor varies from 60% to 70%. The pie chart above leaves out the water vapor
contribution of greenhouse gas affect since it is not man-made. If we consider on average that
water vapor contributes 65% of our GHG, approximate what percent of our total greenhouse gas
production is not water vapor?
2. If 84% of that non-water-vapor gas is CO2, what percent of our total greenhouse gas production is
CO2? Enter that percent in the chart below.
3. Do the same calculations in the chart below for CH4, N2O, and fluorinated gasses.
Approximate % of GHG
generated each year
Greenhouse gas
H 2O
Weight of greenhouse
gas
CO2 equivalence
(CO2e)
65%
CO2
CH4
N 2O
Fluorinated gasses
On the pie chart above, CO2 is the most prevalent non-water-vapor GHG with CH4 coming in second. It is
interesting that methane (CH4) is much more efficient at trapping the earth’s heat radiation than carbon
dioxide (CO2). By weight, methane has more than 20 times greater an affect on climate change than
carbon dioxide (CO2).
Methane is measured in metric tons. Metric tons are units of mass or weight equal to 1,000 kilograms or
about 2,204 pounds. For instance, the average automobile produces about 6 tons of CO2 per year.
I tried to find out the annual production by weight of all greenhouse gases but this was the only lead that I
could find.
Globally, ruminant livestock produce about 80 million metric tons of methane annually, accounting for
about 28% of global methane emissions from human-related activities.1
4. Calculate the tonnage of global methane from this fact and add that weight in a new column of the
chart above.
5. Fill in as much of the weight column in the table above as you can.
6. If methane has 23 times the affect on global warming than carbon dioxide, calculate the CO2
equivalent affect (CO2e) of that weight of methane.
This is actually how the greenhouse gases are measured ... by CO2 equivalence units measured for
100 years of affect (CO2e). The CO2 equivalence factors for the gases already mentioned are1:
Gas
CO2e
CO2
CH4
N 2O
Fluorinated gasses
1
23
296
140 - 11,700
7. In 2010, The Bureau of Transportation Statistics counted 250,272,812 highway vehicles on US
roadways. Remember the before mentioned fact that each vehicle emits about 6 tons of CO2 per
year. About how many tons of CO2 must all of those U.S. vehicles produce?
An adult cow may be a very small source by itself, emitting only 80 - 110 kgs of methane, but with about
100 million cattle in the U.S. and 1.2 billion large ruminants in the world, ruminants are one of the largest
methane sources.
In the USA, cattle emit about 5.5 million metric tons of methane per year into the atmosphere.
8. What is the CO2e (CO2 equivalent) of those American cattle?
9. How does that compare with the US auto emissions?
Not sure that this is verifiably true but answers.yahoo.com claims that;
• The average person farts 30 times a day.
• The average fart is 25cc
10. What is the total volume of fart per person per day?
11. If only 10% of a human fart is methane than how much methane does one person emit in one day?
12. There are approximately 315 million people in the US. How much methane gas do they
collectively emit from just flatulence? (1 metric ton of methane = about 2,150,000 cubic centimeters
of methane.)
13. What is the CO2e of that much methane?
14. Which is worse: cars, cows, or people as GHG producers?
15. Should we give up eating meat?
Source: http://en.wikipedia.org/wiki/Flatulence
http://icp.giss.nasa.gov/education/methane/intro/cycle.html
http://icp.giss.nasa.gov/education/methane/intro/cycle.html
1
http://www.epa.gov/methane/
1
http://www.epa.gov/rlep/faq.html
http://www.ncdc.noaa.gov/oa/climate/gases.html
http://www.epa.gov/climatechange/ghgemissions/
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