Warning! There’s lots of data here, and the numbers are astronomical. After all, we’re talking about the entire planet’s atmosphere. So this should help give you a sense of the numbers:
1 Gigaton = 1,000,000,000 metric tonnes
The estimated weight of Mt. Everest = 3,400,000,000 metric tonnes
Carbon Dioxide (CO2) has become the ruler by which all greenhouse gases are compared. It’s mainly produced by the world’s transportation systems, which send up roughly 6.8 gigatons of Carbon Dioxide (that’s 2 Mt Everests) every year. (link) Carbon Dioxide is released through burning coal, oil, wood, and through deforestation. Similarly, the raising of livestock contributes to this figure mainly in the clearing of forests to graze animals, and in the use of fuels for transporting animals, feed, and supplies. (link)
In terms of cost, I invite you to consider that each ton of CO2 added to our atmosphere causes an estimated $220 in economic damage (I will let you, dear reader, examine the cost of almost 7 gigatons).
You can’t spell ‘carbon,’ without CAR.”
Jeff Speck - 'Walkable City'
While released in smaller amounts, methane is all the more troublesome since it has 72 times the impact on the climate. For transportation, methane is released mainly in oil drilling, through ‘flaring’ or through pipeline leaks. (link) About 14% of the world’s methane is released this way.
Grazing animals, on the other hand produce most of the world’s methane. The combination of ‘cow burps’ with animal waste lagoons and animal feed results in roughly 15 gigatons of CO2 equivalent per year. (link) That said, I want to make an important additional point. By comparison, rice production (the main plant-based source) contributes about 2.7 gigatons CO2 equivalent per year. (link) I include this to point out that there are plant-based sources which have a big impact as well. According to Dr. Masanobu Fukuoka, a well-known permaculture farmer in Japan, rice farming can be done less impactfully by reducing the amount of time that rice fields are flooded.
The third climate changing gas is Nitrous oxide. This potent gas is 300 times as damaging as CO2. So even though it is released in comparably small amounts, it still packs a big punch. Nitrous oxide is mainly produced by agriculture, with livestock contributing 1.5 megatons of CO 2 equivalent each year. (link) By comparison Nitrous oxide emissions from transportation are almost nil.
Even with the wealth of information available though, the issue is not as clearcut as it seemed. The world’s transportation vehicles do produce almost 7 gigatons of CO2. But there’s more to the story then that.
The key element, which Dr. Mitloehner had said was missing from the UN study, was something called ‘embodied energy.’ This is the amount of energy that goes into something before it arrives on a store shelf. The UN study did include the embodied energy for livestock (land use change), but did not include the embodied energy needed to bring a car and it’s fuel to the customer. That’s why, in my research I looked into the whole process, to offer an ‘apples-to-apples’ comparison. It’s difficult to make comparisons between a living being like a cow and an automobile, but bear with me.
just imagine Bill O'Reilly in a thong.
Strømman et. al. Norwegian Univ. of Science and Technology
So going beyond tailpipes and cow burps, where is the rest of the damage coming from? Well the embodied energy for transportation includes a long industrial process. Vehicles don’t operate in a vacuum [no cars in outer space]. The materials have to be mined from the ground, manufactured, and then delivered. Estimates for the pollution created vary widely. From as low as 6.3 tons per vehicle to as much as 30% of a car’s total emissions. (link)
On top of the embodied energy to manufacture vehicles there is also a great deal of embodied energy needed to pump, process, and deliver the fuel. According to this UK report, the embodied energy for fuel is roughly equal for that of vehicle manufacture. They estimate that the embodied energy for both manufacture and fuel at 10% of the vehicle’s lifetime impact. This amounts to roughly 158 million tons of CO2 worldwide. Of course the impact depends largely on the source (offshore, tar sands, or oil shale) and distance that the oil has to be transported.
Lastly we will look at the Greenhouse Gases released for roads. According to this Canadian study, the average carbon emissions for roads comes out to 11 metric Tonnes per sq. km. over a 50 year period. Translating that into a world total gives us almost 35 million tonnes of greenhouse gas released per year around the world.
Though the climate emissions from cars and their infrastructure is enormous, the data nevertheless was showing that the world’s domestic animals produce more climate changing gases then all of the world’s transportation. But wait, there’s even more to this story.
Dr. David Steele of EarthSave Canada wrote an eloquent piece, describing other factors not included in the UN study. In this case the most significant being the Carbon Dioxide exhaled by the millions of cows daily (just like we do). His conservative analysis estimates that 3.2% of world emissions can be attributed to the breathing of livestock. He also suggests an additional 2% increase due to the gas exhaled by farmed fish, which I agree is important. Adding the sum total, we get an additional 3 gigatons of CO2 equivalent.