Arguments
Does breathing contribute to CO2 buildup in the atmosphere?
Posted on 26 September 2010 by climatesight
Guest post by Kate from ClimateSight
The very first time you learned about carbon dioxide was probably in grade school: We breathe in oxygen and breathe out carbon dioxide. Any eight-year-old can rattle off this fact.
More specifically, the mitochondria within our cells perform cellular respiration: they burn carbohydrates (in the example shown below, glucose) in the oxygen that we breathe in to yield carbon dioxide and water, which we exhale as waste products, as well as energy, which is required to maintain our bodily processes and keep us alive.
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
carbohydrates + oxygen → carbon dixoide + water + energy
It should come as no surprise that, when confronted with the challenge of reducing our carbon emissions from the burning of fossil fuels, some people angrily proclaim, "Why should we bother? Even breathing out creates carbon emissions!"
This statement fails to take into account the other half of the carbon cycle. As you also learned in grade school, plants are the opposite to animals in this respect: Through photosynthesis, they take in carbon dioxide and release oxygen, in a chemical equation opposite to the one above. (They also perform some respiration, because they need to eat as well, but it is outweighed by the photosynthesis.) The carbon they collect from the CO2 in the air forms their tissues - roots, stems, leaves, and fruit.
These tissues form the base of the food chain, as they are eaten by animals, which are eaten by other animals, and so on. As humans, we are part of this food chain. All the carbon in our body comes either directly or indirectly from plants, which took it out of the air only recently.
Therefore, when we breathe out, all the carbon dioxide we exhale has already been accounted for. By performing cellular respiration, we are simply returning to the air the same carbon that was there to begin with. Remember, it's a carbon cycle, not a straight line - and a good thing, too!
This post is a new rebuttal to the skeptic argument 'Breathing contributes to CO2 buildup' (written by Kate from ClimateSight). This blog post is the Intermediate version - she's also written a Basic Version that features a simple graphic explaining the carbon cycle from a respiration point of view.
I was searching for a way to tell merkins that they emit too much. The article is severely constrained by space but the really essential point is that there are many nations that ‘emit’ more CO2 from their population breathing than they do from burning fossil fuels.
The rationale for the article was a ‘helpful’ suggestion of a method for the US to further destabilise Kyoto (this was in 2006) by insisting that human respiration be included on the flimsy pretext that enteric methane is included. The idea (from the US pov) would be that China especially would have to pay a greater proportion of its GDP to buy credits than the US.
Please, note the ‘department’ of Eos that this was published in before telling me that breathing does not release fossil CO2.
If plants cant distinguish fossil CO2 from any other CO2, and the concentration of CO2 in the atmosphere has nearly doubled, it is likely that a good part of what we eat has its origin in petroleum.
"And how humans reducing other species on the planet has made any difference."
You could have less diversity in terms of species, but still have more animals numerically in terms of food stock..., but these in turn feed on vegetation.
My big concern is when they start noticing the CO2 that comes from fermenting wine and beer.
Plant a garden on your balcony, and raise chickens in your bedroom!
Ironically, even walking and bicycling isn't a 'carbon' neutral transport due to the greater exertion relative to rest, and food consumed necessary to generate this extra energy! Whilst this is usually insignificant if you are a vegetarian, it is not if a substantial portion of your diet comes from beef and lamb!
Check to see where that plastic bag of chopped up lettuce you purchased at the megamall was grown and processed. In the United states it was likely grown and irrigated in Arizona or California, chopped and packaged in Mexico, and consumed in New York and Maine. In Europe it may have been grown and irrigated somewhere around the Mediterranean, chopped and packaged in Africa, and consumed in Sweden and Norway.
Yes, the carbon footprint of that package of chopped up lettuce is much less than meat, but much, much more than your backyard garden.
I wouldn't count livestock bred for meat or dairy products since even if we became pure vegans, methane producing animals would still roam the earth (think of the vast herds of American bison and don't forget the termites - another source of CH4).
RSVP possibly need not overly fear the addition of wine and beer to our CO2 budget - after all, we discovered the stuff because of natural fermentation (though not all natural fermentation will yield that which gladdens the heart of man - the denizens of the darker recesses of my fridge gladden the heart of none!).
Alas, no matter how impeccably renewable our energy sources, our CO2 footprint must exceed that of respiration particularly since activities such as manufacturing steel and concrete result produce waste CO2.
Hard as we strive to balance our carbon budget, we still fall victim to the relentless laws of thermodynamics spiralling our way to entropy. As John Maynard Keynes cheerily quipped: in the long run, we're all dead.
"This article doesn't really answer the question of whether a massive increase in the human population over the last couple of centuries has had an overall effect on CO2 emissions from breathing."
Yes, it does. It's a cycle; the size of the cycle doesn't matter, it's still a cycle. No matter how many people there are, the carbon they exhale all came out of the atmosphere in the first place.
Of course, this applies only to exhaled CO2. Clearly an increasing population will leads to increasing CO2 emissions in other ways--just not in breathing.
The CO2 we breath out comes from the food we have eaten, it has just been recycled,it isn't NEW CO2, while the CO2 from burning fossil fuels is.
Your response captured the essence of the situation, but it's not really accurate, for a couple of reasons.
First, the CO2 we exhale actually is "new" CO2. Remember, this is a carbon cycle, not a CO2 cycle. The CO2 we exhale was created by respiration.
Second, the carbon in the CO2 generated by fossil fuels burning also came from atmospheric CO2, so it isn't really different from exhaled CO2 in that respect. What's different is that it took millions of years to accumulate, it was sequestered for further millions of years, and we're releasing it over a time span that can be easily measured in decades.
What you said was a fair representation of the practical difference between respiration and fossil fuel burning. No matter. The deniers will still catch you out on such oversimplifications and call you a liar or worse.
Nature adjusted well to the CH4 released by billions of methane-producing animals grazing naturally on the earth for millions of years. It is only recently, since we took to burning huge amounts of fossil fuel to disrupt nature, has this become a problem. To see how we have systematically destroyed the earth, I recommend reading Topsoil and Civilization. The fact that we have systematically destroyed most of the world's topsoil makes climate change effects all the more serious.
Yes I have seen wildly different figures, some placing cattle meat two orders of magnitude above that of vegatables in terms of Carbon equivalent per unit energy others with much less difference. Here is just one source
CO2e from foods
It seems we are digging deep to come up with this topical treatment of the lamest denier tactic "well, stop breathing then!"
But lately the trend has been an excess of the super basic and a paucity of posts based on new journal articles. I hasten to add that I understand the work required to read and understand, let alone recast it in a way that appeals to less knowledgeable folks like myself.
But that is part of what makes skeptical science so great, and I miss it.
Actually, we've been burning biomass for tens of thousands of years and fossil fuel for about 200. My point was that we've been a non carbon neutral species almost since our arrival on the planet. Indeed, as best as I can tell, we are the only non carbon neutral species.
More to the point, much of what we build and consume (aside from food) is not carbon neutral and, failing a major technological revolution, never will be. Even producing the technology required for renewable energy is not a carbon neutral exercise.
I was merely pointing out that it makes little difference whether cattle bred for meat and dairy or free ranging ruminants that do not form part of our food chain roam the world.
I feel a certain wry amusement having been labelled a 'sceptic' that folk don't notice when I'm agreeing with an AGW proposition :-)
Actually, I did notice. :)
A worthy, thought-provoking read is Ruddiman's Plows, Plagues and Petroleum: How Humans Took Control of Climate. Ruddiman contends that human induced climate change began as a result of the advent of agriculture thousands of years ago and resulted in warmer temperatures that could have possibly averted another ice age. A nice graphic for visualization of the ensuing "Golden Age" is:
We'll have to update this graphic around 2030 or 2040, when we hit that IPCC 2-3 degrees C with the legend "Agriculture ends" and an arrow pointing to the date. :(
The Yooper
Using carbon cycle fuels rather than carbon sink fuels could have been managed, or managed better. If carbon cycle fuels had been treated as a crop - with replanting or coppicing or similar processes - we could have maintained some balance. Especially if we'd started out that way and developed and extended those practices with population increase.
The underlying problem is that we've been wasteful, profligate even, with every kind of substance we could use as fuel. Even coppicing was used principally as a way of getting desired form for building materials rather than as a way of maintaining fuel stocks.
No matter how the carbon cycle was affected by fire, domestic animals or anything else, the total store was still limited to the what was available from atmosphere and biomass. You can transfer some from here to there, change the relative importance of some reservoirs and sinks, create new sinks and means of emissions from reservoirs, but there is no net addition to the cycle.
Pulling out what has been stored in the crust for millions of years and injecting it in the cycle is different. That's a true net addition.
Philippe @ 24: Actually, Greece was deforested long before the Common Era - they used heaps of timber for their triremes.
Similarly, large swathes of Croatia were deforested by the Venetians who needed the wood to build the piles upon which much of their city rests today.
In short, even biomass ain't carbon neutral especially if we use it at a rate greater than it can be replaced. Why else did we turn to coal (coal mining is a challenging and dangerous enterprise even today)?
"Using carbon cycle fuels produces ecological changes, using carbon sink fuels produces physico-chemical imbalance in nature, which produces ecological changes."?
The obvious issue that using carbon cycle resources badly can cause damage is a step beyond the simple truth that the breathing of animals, including us, and plants photosynthesizing is a carbon neutral cycle.
Once we move into deforestation or oxidising carbon by exposing and ploughing soils or burning dung instead of using it to replenish soil nutrients, we're beyond this central, simple, obvious point.
"Pulling out what has been stored in the crust for millions of years and injecting it in the cycle is different. That's a true net addition. "
Which almost sounds like there should be more vegetation in the long run.
As long as population increases, however this may not be true, but if stabilized or was to reduce, why not?
As for general ecological vegetation there's a whole lot of discouraging material about interactions between animals, insects and vegetation being disrupted. (Think knocking off the dodo leading to the decline of the trees which had depended on seeds being distributed and fertilised in dodo droppings. Noone saw that coming.)
And our knowledge of how much our crop and useful plants are dependent on other ecological interactions is very much in its infancy. The consequences of imbalances in distribution and concentration of plants which will thrive and those which will decline in an atmosphere with increased CO2 (and ozone, etc) are nearly unknown, and the knock-on effects ... ?
CO2: 'double cheese-burger with no salad, in fact leave the bun and beef out too' for plants.
Plants lock up C02...Plants get 'eaten'....C02 is released.........What is the difference? Of course humans and all veggie eaters contribute to GHG's.
The C02 would remain 'locked in' otherwise.
Henry
Plants which are eaten or die and decompose on the surface return their carbon to the atmosphere... from which it is then re-absorbed by new growth.
Plants which get buried and slowly turn into fossil fuel sequester that carbon away from the atmosphere... until we dig it up and burn it.
One is an ongoing natural cycle with essentially balanced amounts of carbon going into and out of the atmosphere. The other is a human intervention which is putting more carbon into the atmosphere faster than natural processes can absorb it... and thus causing the atmospheric CO2 level to increase.
Thus, even ignoring that all of the carbon we breathe into the atmosphere comes from plants (or animals that themselves got it from plants) which in turn took that carbon OUT of the atmosphere... the total amount from human breathing is much lower than the rate that atmospheric CO2 is growing.
USEIA says 30 Gtons per year for the global total -- and that was 2008.
There's actually a series of invited posts on WUWT by Ferdinand Engelbeen regarding the human causes of CO2 increases, the most relevant to this discussion being Part 1 - showing that the CO2 increase is due to our actions. Parts 2, 3, and 4 are also interesting.
I'm going to have to compliment Anthony Watts for supporting such a clear series of posts that disagree with some of his base arguments!
A typical human contains ~18% by mass C, or about 13 kg for a 70 kg person. So since my birth, I have been recycling tons of carbon (for no net change), but also sequestering about 13 kg of C. If I wasn't there to eat those plants, they would more quickly have rotted and returned the CO2 to the atmosphere. As long as I am breathing, I will continue to sequester my share of C. When I stop breathing, that C will be returned to the atmosphere.
The more people, the more C is sequestered in our collective bodies! (6 billion people) * (0.06 tons/person) --> about 0.1 billion tons of sequestered C.
Basically, any net global increase in biomass will sequester C (for example, the annual variations in CO2 as the plants in the N Hemisphere grow during the spring and summer). Since I personally am 80 kg of biomass, I am sequestering my share of carbon for ~70 years.
(Of course this is a bit simplistic. If people were not around, then other animals would increase to take advantage of the food supplies, and those animals would sequester the C in a similar manner.
And people have cut down forests around the world, returning that sequestered C more quickly. I suspect this effect greatly outweighs the increase in human sequestered C. And both of these are presumably greatly outweighed by the burning of fossil fuels over the last century.)
Why are we talking about breathing as a CO2 source?
Sometimes it isn't enough to simply disprove a 'skeptic' argument with one line of reasoning. If you show it is ludicrous five different ways, stamp it into the ground, set it on fire, and bury it in the mud then maybe they'll consider that it isn't ABSOLUTE proof of the rightness of their opinion.
Another fun fact... the UPPER estimate of CO2 emissions from volcanoes is about 300 million tons per year. Which is only 1/10th the emissions from humans breathing each year... which is itself only 1/10th the emissions from human industry each year.
The simple fact is that all these contributions and variations associated with biological processes within the carbon cycle are totally swamped by us burning materials that are supposed to act as carbon sinks. These materials sequestered their carbon little by little during many millions of years of carbon cycling through these processes and we're releasing them in a couple of dozen decades.
Thus, neither increasing nor decreasing the number of human 'producers of CO2' would have any impact on total atmospheric CO2 levels... we can't increase the atmospheric CO2 level when all of the carbon in our bodies came from the atmosphere. We're just 'temporary storage'.
The structure of the tree enables CO2 to be sequestered into the tree itself and fixed below ground through the root system. Depending on the state of the soil to begin with, this and the buildup of organic matter in the soil itself can result in a permanent increase of carbon storage within the soil.
If instead we focus on the trees, then we realise that the effects of global deforestation not only contribute in the short term a substantial proportion of the annual increase in atmospheric CO2 levels, but are impacting on the long term capacity to permanently lock up carbon in the soil on a large scale.
Last I checked, people do not eat trees.
Maybe there are some differences between species in the amount of exhaled air that is converted from O2 to CO2, but let's assume the whole animal biomass is exhaling ~5% more CO2 and ~5% less O2 than they inhale (and that hasn't radically changed during the industrial revolution). Evidently, the increase in atmospheric CO2 today versus pre-industrial atmosphere is .01% of the total air, but that increase represents only a .2% decrease in CO2 uptake from plants during 250 years.
Where does all the new C added from fossil fuel burning (that isn't retained in the air) end up, if not in the biomass itself?
Or, are humans responsible for diminishing the whole ecosystem (plants and animals), in which case, how much of the CO2 increase can be attributed to the decimation of plant life or other sources, versus how much directly to burning fossil fuels?
Are people really the biggest factor in the whole carbon cycle? Or, does the animal life on Earth (human and otherwise) contribute more CO2 to the carbon flux than fossil fuels?
No doubt the measured increase in atmospheric CO2 is significant, but what is the margin for error in those measurements?
I don't know the answers and I am looking for some educated guesses.
Seek, and ye shall find.
Using your reasoning about humans being neutral in terms of CO2. Following that logic the burning of fossil fuels can be deemed neutral as well. Oil and coal are derived from plants. They just happen to be sequestered in the ground. Its interesting though once taken out of the ground they still don't add to the increase in CO2 as they are in a liquid or solid state. Not unitl they are "burned" do they release CO2. I wonder if that is the same for humans, whether you should be buried or sequestered?