The sandwich: a global warming culprit?

8.6 million cars @1. It is the risk of double (or higher) counting carbons that make me reluctant to embrace such 'cross-field' comparisons. I do not find LCAs to be at all rigorous in that regard.

 

Store or bakery bought bread makes for a lot of transportation, packaging, what have you. Something like rolled oat porridge (from a big bag or rolled oats), not so much.

 

my wife bakes her own bread, but still, the ingredients have to come from somewhere.

 

I heard about this on British radio. Egg and cress was one of the lowest carbon-footprint sandwiches, apparently.

However, it seems that the footprint question only covers production, storage and delivery up to the lips. It ignores post-lip footprints.

Now, in my experience, an egg sandwich leads to significant methane emissions during the post-lip period. And methane is a very powerful greenhouse gas.

I think a delicious egg-onion-and-capsicum sandwich, while its production might not be terribly damaging to the environment, could accelerate climate change quite rapidly if I were to eat it.

 

egg@24. Not methane from you; hydrogen. It is no small task for humans to reset intestinal microbes for methane production. And pop science has left you all thinking otherwise. Or else you're all just ninnies.

Cows, contrarywise, have intestinal architecture quite well suited to methane bacteria. And they are big. And they number a billion and so probably match-weigh humans.

Human food conversion to methane is as nothing. Stop talking about it already. So irritating.

 

The science of "pop!"s.

From my bottom.

 

Anyway....

Not all humans' farts contain methane. But some, it would appear, do. For example, in the study below, of nine people's faeces, five contained archaea capable of producing methane, and four didn't.

Miller TL; Wolin MJ; de Macario EC; Macario AJ (1982). "Isolation of Methanobrevibacter smithii from human faeces". Applied and Environmental Microbiology. 43 (1): 227–32. PMC 241804 . PMID 6798932.

My farts, it would appear, probably do contain methane.

Pimentel, Mark; Robert P Gunsalus; Satish SC Rao; Husen Zhang (2012). "Methanogens in Human Health and Disease". The American Journal of Gastroenterology Supplements. 1 (1): 28–33. doi:10.1038/ajgsup.2012.6. ISSN 1948-9498.

Enjoy your sandwiches, everyone!

 

Or water, if I light it.

 

In order to earn a higher scientific degree, virtually all the students have to perform some original research. There simply isn't enough subjects the public would deem worthwhile for every grad student out there. Then even if something is obvious, an experiment proving it is required for the obvious to be so under the scientific method.

Besides, even stuff that seems not worth it adds to our total understanding.

It is the same scenario as with recycling Styrofoam. Most areas don't because the low density means burning more fuel than it is worth to ship it a plastic plant, and it needs a special compactor to get the density high enough to overcome that hurdle.

Shipping bread has the same issue, but at a lower scale. You can ship more of its ingredients into a truck for the same amount of fuel because they take up less space than baked bread, which is also more delicate when it comes to handling.

Stories about improper use of methane detectors say otherwise about the humans and methane production.

 

Strictly in the interest of science, I once observed a flatulence flammability test. There was a strong odor suggesting a measurable amount of sulfur-based, gas content. We also had a demonstration of the importance of a mesh flame screen.

Having one ignition fail to get a proper fuel-to-air ratio, one of the experimenters demonstrated that hair fails as a flame mesh.

Bob Wilson

 

tmi.

 

I will not claim my experience observing ignition of flatulence was scientific. Purely entertainment OK? About half of gas passers could support ignition. Also, that was not a statistically unbiased sample. It was college; perhaps the most statistically biased sample one could address.

Hydrogen must be 4% or more in air to ignite, methane 5%. This clearly can occur with H2 but what about CH4? My recommended 1 article to read on the subject:

"Stability of human methanogenic flora over 35 years and a review of insights obtained from breath methane measurements"

From 2006; they sampled lung exhalation not 'the other end' but they justify that. Also it is free to download.

In their sampled population about 1/3 produced methane at all. Other regional studies have gone as high as 3/4. So, there is methane, but not from everyone.

Also, not much. 11 ppm was their average for producers. This is far below 5%. Scaling from one end of digestive tract to the other was not done, but this study does not support that CH4 ever dominates. OTOH we know that H2 does.

So, maybe it's about halfsies that you produce methane. If so it is in tiny quantities. Ruminant animals we raise for meat and milk are quite otherwise. So if you consume those things, that's your methane footprint. That and wetland rice. Not 'internal activity'.

Human solid waste can be transformed quantitatively into methane (biogas). Happens by microbes under conditions very different from in your intestines. Which I would assert is a very good thing.

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Other paywalled articles appear to make tail-end CH4 measurements. If youse guys are really hot on the subject. I suppose I'll go after them. Sigh.

 

yes, please don't.

 

Clarifying, I do not know that flatus H2 ever exceeds 50%. Dominant gas is CO2, unless you are a 'swallower' in which case N2.

Much more CO2 though, from stem than stern. Are we done with this yet?

 

here I thought we could save this thread with some nice sandwich recipes...

 

or a visit to the earl...

 

For those without the appropriate science background, odorless methane is often mistakenly attributed to smelly flatulence. But as many of the enlightened here know, it's really the sulfur containing compounds, predominantly H2S, that produce the familiar malodor.

Curious fact - although humans have an underdeveloped sense of smell compared to many other mammals, we are able to detect sulfur containing compounds in minute quantities (<10 parts per billion) that about places us among dogs for these particular substances.

 

Odorlessness of methane is really dangerous. After a big people-killing explosion (forget where) a sufur odorant was added to methane gas as normal practice.

Tech copies Nature once again.

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Must be known that flatus has many different smells. Thus, not all H2S. Take a straight carbon chain and put an N on each end. Bam. Stinky. Plus that family of chemicals has amusing informal names.

==
Beef and rice aside, methane mining is still (allowed to be) a pretty leaky process. So your footprint (if you use typical electricity) includes that.

 

For those without the appropriate science background@37. Dammit, I am trying to get you to realize that science will seriously up-fun your lives. Probably you have some things going on more important than that. But just possibly, not as many as you think.

 

i got nothing going on.