You might have heard that cow farts are bad for the environment since they contain methane, so where does that leave human farts?
Human farts may contain methane and other greenhouse gasses, which are not good for the environment.
However, when looking at the bigger picture, human flatulence is only a small unavoidable component compared to fossil fuel emissions and agriculture.
Here’s everything you need to know about the environmental impact of human flatulence.
1. Are Human Farts a Greenhouse Gas?
When we think of greenhouse gasses, we think of the likes of smoke or car emissions, not necessarily gasses coming from humans.
With that said, technically, human farts are partially comprised of greenhouse gasses.
The most common greenhouse gasses in the atmosphere are carbon dioxide, methane, water vapor, ozone, and nitrous oxide – some of these compounds are in human farts, which is why they’re considered a greenhouse gas.
Studies found that about 25% of an average fart are actually simply oxygen and nitrogen from air we swallowed.
The remaining 75% of a fart are predominantly hydrogen (not a greenhouse gas), but also contain CO2, potentially some methane, as well as some other gasses in fairly small quantities.
2. Do Human Farts Release Methane into the Atmosphere?
There are several different components in human farts, and some people’s farts do contain methane.
As mentioned, farts almost always contain hydrogen, nitrogen, oxygen, carbon dioxide, and hydrogen sulfide – but not necessarily methane.
The compounds in our farts and the amount of each varies from person to person and is also influenced by diet.
Everyone’s microbiome is different, which is why you might have noticed that even if two people eat the same diet, their farts do not actually smell the same.
Gut flora may be influenced by genetics, diet, and environment, which is why families often have similar microbiomes.
Some people are also gassier than others, even if they eat similar diets.
The bacteria in our gut are what produce the gasses in flatulence by breaking down the food we eat.
Interestingly enough, not everyone has the type of gut flora that produces methane.
Research found that out of 16 participants (6 female and 10 men), only 5 (31%) released methane throughout the four-hour study.
Given that methane is more potent than carbon dioxide when it comes to the greenhouse effect, this is good news.
The average fart had a volume of 100 ml (3.3 ounces) – so even for those who do produce methane, this would mean only a small amount of methane per fart.
Approximately a quarter of a fart is made up of oxygen and nitrogen, with the remaining three quarters coming from carbon dioxide, hydrogen, and methane.
Another study on ten volunteers found that only three of them produced methane in varying amounts, confirming the findings of the previously mentioned study that only about 30-40% of humans produce methane in their guts.
Those who ate a fiber-free diet produced less flatulence, less carbon dioxide, and no hydrogen – but it’s not realistic for humans to remove fiber from their diets to reduce emissions since it’s vital for good digestive health.
Methane can also be excreted from breathing. Out of 126 participants in a study, only 36% produced methane from their breath.
Of the 36% of participants, 15 methane producers and nine control participants were studied further to determine if fiber altered methane production.
They found that after adding more fiber to their diets, there was not a significant difference in methane excretion.
The study also noted that two participants stopped secreting methane while control participants began to excrete methane, suggesting methane production is not consistent in humans.
3. Do Human Farts Contribute to Climate Change?
Since human farts contain greenhouse gasses, they can technically contribute to climate change.
With that said, they’re not the biggest culprit when it comes to climate change, and there’s nothing we can do to alter human bodily functions anyway.
Although research has found that diet can change the chemistry of our farts, expecting everyone to alter their diet is unfeasible.
Human farts are not a major player when it comes to the climate crisis, and diet does not seem to change whether humans emit methane or not.
The biggest offender when it comes to climate change is fossil fuels, making up 90% of all CO2 emissions globally and 75% of greenhouse gas emissions in general – so, the amount human farts contribute is negligible.
As mentioned earlier, since everyone’s diet and digestive system are different, some people naturally have less of an impact than others.
4. What’s Worse for the Environment: Human or Cow Farts?
Since humans greatly outnumber cows, with 1.4 billion cows on Earth and 8 billion humans, you might think that humans are the bigger offender, but this is not the case.
Since our diets and digestive systems are so different, human and cow farts are not the same.
Plus, most methane cows produce is actually from burping rather than flatulence.
According to this study, the average human fart volume is 705 ml per day, but only 68 ml of that (less than 10%) is the greenhouse gas CO2.
70% of the study participants produced no methane at all, and among those that did produce methane, it accounted for as little as 0.4% to at most 17% of the fart volume (3 ml to 120 ml).
Based on these numbers, one person produces 24.8 liters of CO2 per year.
If we further take into account the fact that only 30% of people produce methane at all, the calculated methane emissions per person range from only 0.3 to a maximum of 13 liters per year.
Compared to that, one cow alone can emit up to 200 kg (440 lbs) of methane per year.
Around 60% of the methane in the atmosphere is due to human activity, with the rest from nature, such as wetlands.
So when it comes to methane from farts and digestion, cows produce more than humans.
So, since methane has more of a warming effect than CO2, the biggest concern is increasing levels of methane in the environment.
Methane levels have almost tripled pre-industrial levels – but the biggest contributors to methane levels are wetlands, fossil fuel extraction, livestock, and landfill and agricultural waste, respectively.
With that said, it may be possible to reduce how much methane cows produce by altering their diets.
Cows are mostly fed grass, hay, grass silage, maize silage, and concentrated feed made up of potato fiber and maize meal.
Feeding cows younger grass may reduce methane emissions by 30%.
However, since nitrogen can be an issue for livestock as it can create ammonia, this type of grass is not a perfect solution.
Relying more on maize silage may reduce methane and nitrogen emissions from cows.
Adding seaweed to the cows’ diet may also reduce methane emissions.