First, what is global warming?

Basically, a layer of greenhouse gases (primarily water vapor, carbon dioxide, methane and nitrous oxide) absorb infrared radiation and trap heat inside the atmosphere of the earth (like a blanket) and it causes the surface to be a little bit warmer.

Methane is a greenhouse gas like carbon dioxide. However, methane negatively effects the climate 23 times more than carbon dioxide does. So what does this have to do with cows? Well, cow gas and manure contains a lot of methane. All ruminants, or animals that regurgitate their food and then re-chew it produce methane.  Combined, these animals emit about two billion metric tons of carbon dioxide equivalents per year.

On average, a cow releases 70-120 kg of methane per year. So after doing the math, if a cow produces 100 kg of methane in a year, that equals 2,300 kg of carbon dioxide. But how much is 2,300 kg of carbon dioxide?

The average car had to drive 7,800 miles to produce 2,300 kg of carbon dioxide. That means you could drive 7,800 miles per year and produce the same effect on the environment that a cow does in one year of just pooping.

The average American drives 13,476 miles per year (according to the Federal Highway Administration).

So two cows have a larger carbon footprint than the average American driver.

There are about 1.5 billion cows and bulls on the earth right now.

In 2011 the number of cars reached 1 billion in the world (sorry I can’t find anything more recent than 2011).

Therefore (if I did my math right): All of the cows on the planet make ¾ as much green house emmisons as all of the cars on the planet make.

However, that is only compared to the cars that people drive personally, that does not account for all of the planes, trains, and trucks that are constantly transporting people and goods around the world.

The official statistic that I found was from the Food and Agriculture Organization of the United Nations, said: agriculture is responsible for 18% of the total release of greenhouse gases worldwide. (This is more than the whole transportation sector).

There is another reason why this number is so large that I have yet to mention: with all of these cows, there is a need for more land for them to graze. The clearing of tropical rain forests to get more grazing land is responsible for another 2.8 billion metric tons of carbon dioxide per year.

Livestock take up 30% of the earth’s entire land surface. Plus, 33% of all farm land is used for producing food for livestock.

In Latin America, about 70 % of former forests in the Amazon have been cleared for grazing. Having more cows leads to the production of more greenhouse gases and having more cows leads to less trees and forests. But trees and forests are essential because they are what removes the greenhouse gas carbon dioxide from the air! Basically cows are harming the environment from two angles.

But why are there so many cows that this has actually become a problem? Today more people have more money to buy more food. There has been a considerable increase (62% since 1963) in the available food consumption of meat worldwide. While many developed countries meat consumption has stayed relatively stable, there has been an increase in developing countries. Most developing countries such as Brazil, have seen a threefold increase, but China has seen a dramatic ninefold increase in their total meat consumption. (Kearney J., Food consumption trends and drivers. Philos. Trans. R. Soc. Lond. B Biol. Sci. 2010; 365:2793–807.)

A Japanese study showed that producing one kilogram of beef leads to the emission of greenhouse gases with a global warming potential equivalent to 36.4 kg of carbon dioxide.

It is also interesting to note that it also consumes 169 mega joules of energy. This is enough energy to light a 100-watt bulb for nearly 20 days.

Table: http://timeforchange.org/are-cows-cause-of-global-warming-meat-methane-CO2 (Take this table with a grain of salt; I don’t know how reliable this source is, I just wanted to capture the overall trend.)

So what conclusions can we gain from this?

While it is not a fact that cows are the cause of global warming, it is a fact that they contribute considerably to the amount of greenhouse gases emitted. What we also know for sure is that it is environmentally friendly to eat less meat and dairy products. It is one of the simple ways that you can reduce your own personal carbon footprint and your own negative impact on the environment.