Silent but Deadly: The Global Warming Impact of Human Flatulence
As a climate consultant, I am very fortunate to work in a field that is exceptionally relevant, interesting, and perfectly aligned with my personal interests and passions. I spend much of my free time reading books, articles and the latest research on climate change-related topics, and as a bonus, it keeps me up-to-date and sharp as a knife in my line of work.
No, flatulence is not also a passion of mine, but calculating greenhouse gas emissions and the impact on climate change of companies, activities, products, and services is a big part of what I do from 9 to 5, and is something that often occupies my mind in my free time.
Now, we all probably know by now that agriculture is a big contributor to global greenhouse gas emissions, contributing roughly 12% to our global footprint. This is not ideal but is understandable considering we have almost 8 billion mouths to feed. Most of these mouths have a fondness for dairy products and meat, especially beef, which contributes about 60kgCO2 per kg (compared to most fruit and vegetables which emit less than 1kgCO2 per kg). The majority of these emissions are as a result of the cow’s digestive processes which cause methane to come out of both ends. This is significant, since methane is 34 times more potent as a greenhouse gas than carbon dioxide over 100 years.
This led me to thinking about us humans — we also have gases escaping our bodies from time to time (some much more than others). A bit of a google search showed that some had asked how this might impact global emissions before, but it seems no one had done any proper calculations. So, I decided to give it a go, and the results were surprising…
Let’s get technical
First, we need to make some assumptions. A study done in 1994 found that on average, a person ‘emits’ 705mL of gas a day. Of this gas, roughly 50mL is methane and 68mL is CO2. What this study also found was that only 3 in 10 people emit methane as a result of differences in gut biomes. Using this information, the fact that there are about 7.8 billion people on the planet, and the density of these gases, I calculated the following:
Global annual Methane emissions from human flatulence = 27,931,173kg
Global annual CO2 emissions from human flatulence = 384,159,551kg
Since methane is 34 times more potent as a greenhouse gas, we can combine these as a total carbon dioxide equivalent footprint (which is the standard way of reporting greenhouse gas emissions), resulting in:
Global annual carbon footprint of human flatulence = 1,333,819 TonnesCO2eq
Now the above number may seem like a lot, so I’ll try put it into perspective in several interesting ways. First, let’s make it seem rather insignificant:
The carbon footprint of human flatulence only contributes 0.0027% to global emissions
Meh, nothing wrong with letting off a bit of gas then it seems. Now, let’s tell a different story using the same data point (annual emissions per country can be found here):
Global emissions from human flatulence are more than the annual emissions of Bermuda, Samoa, The Cayman Islands and the Solomon Islands COMBINED
Sounds a bit more worrying doesn’t it? These tiny island nations obviously have very small carbon footprints, but an article with a sensational headline like this will probably have a few people advocating for us all to eat less beans. Let’s try another one:
Global emissions from human flatulence is equivalent to driving a medium sized car 200,000 times around the Earth
Of course, in the global scheme of things this is highly insignificant. Per person fart emissions is about 0.17kgs of CO2 a year, this is about the same as driving your car 1km. Take a shorter route tomorrow, fart with a clear conscious for the rest of the year.
A fine balance
The caveat to all of this of course is that human flatulence is a natural process and the CO2 that we release is sequestered by crops that we grow and eat again, and so the cycle continues. There are other processes that form part of the natural carbon cycle that release CO2 on a much bigger scale than what I calculated above. To say that human flatulence contributes to global warming is therefore misleading of course (and here I’ll apologize for my hypocritically sensational article headline). So fart all you want — the calculations above were just a fun exercise and are nothing to be concerned about.
However, our planet and everything on it coexist in a fine balance. Carbon dioxide only makes up about 0.041% of Earth’s atmosphere, but if we increase this to anything above 0.08% we’re looking at a roughly 4°C warmer world which will be damn near uninhabitable — such is the fragility of this balance. We have already increased this concentration to levels never before seen in recorded history, or within the last million years.
Sooo…what am I supposed to do?
The world has already warmed by about 1°C but we genuinely have a shot at limiting any further warming to 2°C. Even this level of warming will have disastrous consequences, but consider it a survivable fender bender as opposed to a complete write-off. Governments, companies and individuals all have a part to play and every small action contributes. Here are some simple actions you can take (in no particular order):
1. Eat less meat
2. Drive less (or drive electric)
3. Fly less
4. Buy less and buy better
5. Use less energy (or go green)
6. Instigate and drive climate action within your company
We often forget that our sphere of influence as individuals is not only limited to our lifestyle choices but also extends to our work, which is what many of us spend 5 days a week doing. Regardless of your role or position, you have the power to instigate action or at least raise awareness. So, if you love your steaks and overseas holidays too much, then my absolute number one recommendation is to get your company to take meaningful climate action (and feel free to eat all the beans you want while you’re at it).
