What-If 0017: "Green cows"

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What-If 0017: "Green cows"

Postby Vroomfundel » Tue Oct 23, 2012 9:20 am UTC

http://what-if.xkcd.com/17/

To optimize exposure, cows will need to lie on their belies with their legs spread... that's going to be kind of funny. Or maybe on their backs? Depends on which side will be endowed with the more chlorophyll.

Reminds me of this weird critter: http://www.wired.com/wiredscience/2010/01/green-sea-slug/ - an animal that photosynthesises
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Re: What-if 0017: Green cows

Postby AvatarIII » Tue Oct 23, 2012 10:10 am UTC

your link is to 16

eh, this one feels phoned in, very little "what if we had more power?", I was thinking maybe, what if green cows had big fins that could fold away at night, how big would the fins have to be to keep cows well fed, and therefore how much extra farmland would be needed to make room for these giant-finned cows.
How much energy would then be saved by not needing a digestive system? which you could start by asking how much energy is wasted producing 100 litres of saliva per day?
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Re: What-if 0017: Green cows

Postby Vroomfundel » Tue Oct 23, 2012 11:37 am UTC

corrected

Indeed, not as much speculation as I was hoping for. Specifically about the fins, they'll have to have a sunlit surface of 48 square metres as per Randall's calculation. I guess with radiator-style folding we can get a reasonably good volume to exposed surface ratio but these are still going to be huuge fins
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Re: What-if 0017: Green cows

Postby AvatarIII » Tue Oct 23, 2012 12:25 pm UTC

Vroomfundel wrote:corrected

Indeed, not as much speculation as I was hoping for. Specifically about the fins, they'll have to have a sunlit surface of 48 square metres as per Randall's calculation. I guess with radiator-style folding we can get a reasonably good volume to exposed surface ratio but these are still going to be huuge fins


...and I suppose if cows had no reason to walk about to graze, they would end up wasting away and not having a particularly good meat yield, which would defeat the purpose (I guess they'd have a better leather yield though).
I guess I'm wondering, would photosynthesising cows with big 48m^2 worth of fins that don't walk around, be more space efficient than normal sized cows that do walk about.
also, if the cows were genetically engineered rather than evolved, there would be no limit to what percentage of the day the cows could be lit. if the cows were lit by electric light during the night all year the fins could be smaller, but how much would it cost per cow in electricity? would the carbon emissions of power plants generating the electricity be better or worse than the carbon emissions by methane produced by cows, which, no longer eating, would be zero, as well as the CO2 used up by the cows photosynthesising 24/7.

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Re: What-if 0017: Green cows

Postby Barstro » Tue Oct 23, 2012 1:03 pm UTC

Vroomfundel wrote:corrected

Indeed, not as much speculation as I was hoping for. Specifically about the fins, they'll have to have a sunlit surface of 48 square metres as per Randall's calculation. I guess with radiator-style folding we can get a reasonably good volume to exposed surface ratio but these are still going to be huuge fins


There's an interesting math problem;
How efficient would cattle's ability to photosynthesize need to be to become viable?

Assuming you are correct grass-fed cattle need 48 square metres per head based on average sunlight and 3-6% efficiency (and factoring in other benefits/detriments of having grass growing in that area vs. finding some other use for the real estate during the day), what is the sweet spot between efficiency of photosynthesis and the size of cow-fins?

How much land does a cow need to live without further intervention (nobody tilling the land, planting seed, fertilizing, or taking away manure?

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Re: What-if 0017: Green cows

Postby asymptotically » Tue Oct 23, 2012 1:10 pm UTC

Most importantly, there are 42 bottles of cow saliva on the racks

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Re: What-if 0017: Green cows

Postby five dollars » Tue Oct 23, 2012 1:11 pm UTC

Wait, cows use 50 megajoules per day? Don't humans only use, like, 8 or 9 (2000 kcal, and 1 cal = a little more than 4 J)? What do cows do that uses so much more energy than humans?

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Re: What-if 0017: Green cows

Postby asymptotically » Tue Oct 23, 2012 1:16 pm UTC

They generate a lot of saliva. I bet it requires a lot of energy to drool out 42 shelved bottles of it.

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Re: What-if 0017: Green cows

Postby AvatarIII » Tue Oct 23, 2012 1:24 pm UTC

five dollars wrote:Wait, cows use 50 megajoules per day? Don't humans only use, like, 8 or 9 (2000 kcal, and 1 cal = a little more than 4 J)? What do cows do that uses so much more energy than humans?


probably digesting all that cellulose, a moot point when they don't need a digestive system any more.

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Re: What-if 0017: Green cows

Postby rmsgrey » Tue Oct 23, 2012 2:16 pm UTC

five dollars wrote:Wait, cows use 50 megajoules per day? Don't humans only use, like, 8 or 9 (2000 kcal, and 1 cal = a little more than 4 J)? What do cows do that uses so much more energy than humans?

The average cow is about ten times the mass of the average human, so cows are using roughly half as much energy as the equivalent mass of humans...

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Re: What-if 0017: Green cows

Postby Fire Brns » Tue Oct 23, 2012 2:34 pm UTC

I've always wondered how photosynthetic animals would work. I suppose if you had more transparent flesh and deeper chlorophyll cells you could boost the input a bit (but increase UV sun damage) and may be even more energy efficient if it just sits around and only moves if a predator shows up.

But then fields would just grow out of control and the grasses would take their revenge on humanity by having wild animals attack you every 5 feet you walk through them.
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Re: What-if 0017: Green cows

Postby mathmannix » Tue Oct 23, 2012 2:39 pm UTC

AvatarIII wrote:probably digesting all that cellulose, a moot point when they don't need a digestive system any more.


Hehe, moot point.
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Re: What-if 0017: Green cows

Postby Vroomfundel » Tue Oct 23, 2012 2:48 pm UTC

AvatarIII wrote:
five dollars wrote:Wait, cows use 50 megajoules per day? Don't humans only use, like, 8 or 9 (2000 kcal, and 1 cal = a little more than 4 J)? What do cows do that uses so much more energy than humans?


probably digesting all that cellulose, a moot point when they don't need a digestive system any more.


... and producing saliva :-D

That's a good point though, does the cow energy expenditure include the amount of energy spent on digesting food? If we want to do precise calculations on the viability of substituting one form of energy source to another we should take "net gain", into account, i.e. subtract the food digestion energy expenditure, which - with celluslose - is indeed going to be pretty high. This might be an important correction in the calculations - but with a quick search I couldn't find any specific numbers for cellulose breakdown energy consumption. I guess these are quite difficult to come by (at least precisely) as that's not happening by use of enzymes and other natural means but through symbiosis with the gut fauna.
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Re: What-if 0017: Green cows

Postby AvatarIII » Tue Oct 23, 2012 2:50 pm UTC

mathmannix wrote:
AvatarIII wrote:probably digesting all that cellulose, a moot point when they don't need a digestive system any more.


Hehe, moot point.


:lol: nice.

http://en.wikipedia.org/wiki/Ruminant#R ... crobiology
Vertebrates lack the ability to hydrolyse beta [1-4] glycosidic bond of plant cellulose due to the lack of an enzyme celulase. Thus ruminants must completely depend upon the microbial flora, present in rumen or hindgut, so as to digest cellulose. Digestion of food in rumen is primarily carried out by the rumen microflora which contain dense populations of several species of bacteria, protozoa, sometimes yeasts and fungi. It is estimated that 1mm of rumen contains 10-50 billion bacteria, 1 million protozoa and several yeasts, fungi.[13]

As the environment inside a rumen is anaerobic, most of these microbial species are obligate or facultative anaerobes which can decompose complex plant material such as cellulose, hemicellulose, starch, proteins. Hydrolysis of cellulose results in sugars which are further fermentated to acetate, lactate, propionate, butyrate, carbon dioxide and methane.

During grazing, ruminants produce large amount of saliva. Estimates are within 100 to 150 litres of saliva per day for an adult cow.[14] The role of saliva is to provide ample fluid for rumen fermentation and as a buffering agent.[15] Rumen fermentation produces large amounts of organic acids and thus maintaining the appropriate pH of rumen fluids is a critical factor in rumen fermentation.


it seems the saliva production is an important step in cellulose digestion.

http://en.wikipedia.org/wiki/Ruminant#R ... ate_change
Methane has 23 times the warming potential of carbon dioxide and its production by ruminants may contribute to a greenhouse effect or climate change. Methane production by animals, principally ruminants, is estimated 15-20% global production of methane.[20][21] The rumen is the major site of methane production in ruminants.[22]


photosynthetic cows could be the best way to save us from the greenhouse effect :D
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Re: What-if 0017: Green cows

Postby Coming_curse » Tue Oct 23, 2012 2:56 pm UTC

What if we took not just chlorophyll but also carotenes and put all the photoactive cells into the hair (and maybe used a little styling gel :mrgreen: ) to maximize the surface area? Shouldn't this increase the amount of energy quite a lot?
One could also play with reflecting skin to get more of the scattered light ...

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Re: What-if 0017: Green cows

Postby Barstro » Tue Oct 23, 2012 3:04 pm UTC

Fire Brns wrote:But then fields would just grow out of control and the grasses would take their revenge on humanity by having wild animals attack you every 5 feet you walk through them.


I'm not so sure. These cows need to use their fins to soak up a lot of light, and a place to stand to do all that soaking. I see them going out to fields in the morning, soaking up the sun, and going back in the evening. None of the light will reach the field, and we will have a lot of barren areas.

In regards to the cows not needing to move, and thus using up less energy;
Cows that don't move could make for some very fatty beef. Good if marbled, bad if it isn't.

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Re: What-if 0017: Green cows

Postby Fire Brns » Tue Oct 23, 2012 3:24 pm UTC

rmsgrey wrote:
five dollars wrote:Wait, cows use 50 megajoules per day? Don't humans only use, like, 8 or 9 (2000 kcal, and 1 cal = a little more than 4 J)? What do cows do that uses so much more energy than humans?

The average cow is about ten times the mass of the average human, so cows are using roughly half as much energy as the equivalent mass of humans...

I assume that is because we have more active metabolisms and also our brains use 20% of our caloric intake which I believe cows do not have the same energy draw.

Human brain: I wonder how much energy cow's use, how could we make cows more energy efficient, why do cows stand north-south, why do they produce so much spit?
Bovine brain: Time to eat grass.
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Re: What-if 0017: Green cows

Postby ahammel » Tue Oct 23, 2012 4:23 pm UTC

Coming_curse wrote:What if we took not just chlorophyll but also carotenes and put all the photoactive cells into the hair (and maybe used a little styling gel :mrgreen: ) to maximize the surface area? Shouldn't this increase the amount of energy quite a lot?
Leaving aside the problem that hair isn't made of cells, you would have problems transporting water and sugar in and out of something that thin. There's a reason that leaves are bigger than that.
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Re: What-if 0017: Green cows

Postby burnt_sheep_den » Tue Oct 23, 2012 4:43 pm UTC

Sidenote: Noticing Randall's use of Rhode Island as a handy unit of area again, I wondered how it translated to the more common European unit: a Belgium (http://www.sizeofbelgium.com/pmwiki.php.)
Turns out they are one order of magnitude apart: 3140 sq km for RI, and 30530 sq km for the Belgium.

So Europeans can handily substitute "1/10th a Belgium" whenever seeing "Rhode Island".

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Re: What-if 0017: Green cows

Postby mathmannix » Tue Oct 23, 2012 4:46 pm UTC

ahammel wrote:Leaving aside the problem that hair isn't made of cells, you would have problems transporting water and sugar in and out of something that thin. There's a reason that leaves are bigger than that.


I think I learned that hair was dead cells... is that wrong?

Fire Brns wrote:Human brain: I wonder how much energy cow's use, how could we make cows more energy efficient, why do cows stand north-south, why do they produce so much spit?
Bovine brain: Time to eat grass.


This is precisely why eating cow brains doesn't make people smarter. Cannibalism is the only way.
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Re: What-if 0017: Green cows

Postby Mikeski » Tue Oct 23, 2012 4:55 pm UTC

Vroomfundel wrote:Reminds me of this weird critter: http://www.wired.com/wiredscience/2010/01/green-sea-slug/ - an animal that photosynthesises


The ones that steal Portuguese Man-o-War stingers are cooler, though.

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Re: What-if 0017: Green cows

Postby ahammel » Tue Oct 23, 2012 6:56 pm UTC

mathmannix wrote:
ahammel wrote:I think I learned that hair was dead cells... is that wrong?

Apparently not entirely. Wikipedia tells me that the outer surface is a layer of dead cells, and the rest is just keratin.
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Re: What-if 0017: Green cows

Postby yellow103 » Tue Oct 23, 2012 7:16 pm UTC

I was hoping for some sort of find a way to power cows with electricity, and possibly nuclear powered cows.

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Re: What-if 0017: Green cows

Postby jay35 » Tue Oct 23, 2012 7:34 pm UTC

I would have liked more extrapolation as well. Easy hypotheticals abound:

What if the cows were larger?
What if the cows were fed different feed?
What if we used elephants instead?
Or mammoths?
How about sea rays?
What if we turn the energy concept on its head and posit plants eating instead of photosynthesizing? How much more energy would that create? What would be the effects of that on earth's ecosphere, climate, food chain, etc?

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Re: What-if 0017: Green cows

Postby Whizbang » Tue Oct 23, 2012 8:08 pm UTC

jay35 wrote:What if we turn the energy concept on its head and posit plants eating instead of photosynthesizing? How much more energy would that create? What would be the effects of that on earth's ecosphere, climate, food chain, etc?


Like the Venus Fly Trap?

What if we were to set up solar panels and convert the sun light for the cows, then feed it through a "series of tubes" into their systems as usable calories?

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Re: What-if 0017: Green cows

Postby Mikeski » Tue Oct 23, 2012 10:01 pm UTC

AvatarIII wrote:eh, this one feels phoned in, very little "what if we had more power?", I was thinking maybe, what if green cows had big fins that could fold away at night, how big would the fins have to be to keep cows well fed, and therefore how much extra farmland would be needed to make room for these giant-finned cows.
How much energy would then be saved by not needing a digestive system? which you could start by asking how much energy is wasted producing 100 litres of saliva per day?

"What if we had more power?" is kinda answered in the article; if photosynthesis could give it 4% of the energy it needed, you need a cow 25 times larger that uses no more energy than the original-sized one (so: with fins that fold out that far. pteradac'ttle! "Radiator fins" would shade each other and not help.). Or you need some combination of fins and much more efficient photosynthesis. Since 100% efficient photosynthesis is off the table due to silly laws about thermodynamics, we need at least something more flying-squirrel-like or bat-like.

They'd still need a digestive system (though maybe a lower-power one) since the cow has to be made out of something, and photosynthesis doesn't convert directly to matter, it just lets the organism build stuff out of the the water and nutrients it gets from "digesting" its environment (roots, or sometimes trapped insects like flytraps or pitcher plants).

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Re: What-if 0017: Green cows

Postby bmonk » Tue Oct 23, 2012 10:28 pm UTC

On the other hand, a photosynthetic cow--where the photosynthesis was an assist to the cow's normal digestion--could survive in more extreme conditions. Perhaps in deserts where there is little vegetation available, as long as they had access to water?

They would also have to have some sort of adaptation to ingest soil or other matter, since they would not be taking in so much food.
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Re: What-if 0017: Green cows

Postby KarenRei » Wed Oct 24, 2012 2:06 am UTC

Yeah, Randall made a huge error. He took the "3-6%" efficiency figure for photosynthesis and went wild with it.

The basal metabolic rate of a 450kg cow is around 25 MJ/day (a human uses about 7, give or take). We can assume that a cow that did nothing but soak up the sun wouldn't use much more than its basal rate. The cow should be being credited with the full 11% efficiency of photosynthesis, not the biomass-creation figures. That's nearly 5 MJ. So the "green cow" isn't 1 1/2 orders of magnitude off it's only half an order of magnitude off. Said green cow simply needs to lose that giant energy-consuming digestive system, some of that muscle mass, and generally lighten up everything to account for the weight reduction, and stretch out that surface area with skin that droops all the way to the ground, and it could probably pull it off. I picture something more like a deer or antellope with extreme drooping skin and maybe taller, lankier legs and a weaker frame.

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Re: What-if 0017: Green cows

Postby ijuin » Wed Oct 24, 2012 7:57 am UTC

A big problem with a photosynthesizing mammal (or any warm-blooded creature) is that even for something as large as a cow, nearly half of its energy consumption at rest is spent on just keeping warm in temperate weather. For smaller mammals such as mice, the fraction of resting energy expended on body heat is well over seventy percent, which is why they need to eat nearly their own body mass in food per day.

Because of this, it may be more profitable to use cold-blooded creatures (reptiles, amphibians, or shallow-water fish) as a source of photosynthesizing meat, as their metabolic energy requirements are lower (plus they won't look strange since many of them are already green!). Consider how much less you have to feed a fish kept in an aquarium as compared to a mouse of equal body mass.

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Re: What-if 0017: Green cows

Postby AvatarIII » Wed Oct 24, 2012 8:23 am UTC

ijuin wrote:A big problem with a photosynthesizing mammal (or any warm-blooded creature) is that even for something as large as a cow, nearly half of its energy consumption at rest is spent on just keeping warm in temperate weather. For smaller mammals such as mice, the fraction of resting energy expended on body heat is well over seventy percent, which is why they need to eat nearly their own body mass in food per day.

Because of this, it may be more profitable to use cold-blooded creatures (reptiles, amphibians, or shallow-water fish) as a source of photosynthesizing meat, as their metabolic energy requirements are lower (plus they won't look strange since many of them are already green!). Consider how much less you have to feed a fish kept in an aquarium as compared to a mouse of equal body mass.


We're not talking about small mammals though, cows are pretty big.

and I'm not sure, but I'm guessing there must be some reason that the biggest reptiles in the world are smaller than cows. I'd possibly consider that at larger sizes, warm blooded creatures/mammals are more efficient.

Then there's the fact that reptiles are rarely if ever cultivated for food.

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Re: What-if 0017: Green cows

Postby Arancaytar » Wed Oct 24, 2012 9:36 am UTC

Cow saliva is clearly the food of the future. Tasty and nutritious.
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Re: What-if 0017: Green cows

Postby mathmannix » Wed Oct 24, 2012 2:11 pm UTC

AvatarIII wrote:
ijuin wrote: Because of this, it may be more profitable to use cold-blooded creatures (reptiles, amphibians, or shallow-water fish) as a source of photosynthesizing meat, as their metabolic energy requirements are lower (plus they won't look strange since many of them are already green!). Consider how much less you have to feed a fish kept in an aquarium as compared to a mouse of equal body mass.


Then there's the fact that reptiles are rarely if ever cultivated for food.


Wow, maybe not in the UK, but definitely in the American South. Alligator meat is considered a delicacy in cajun cooking. (I've never eaten gator, but I have eaten rattlesnake. Very greasy.) What about you Aussies? I know you have Crocodiles, I saw Crocodile Dundee...
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Re: What-if 0017: Green cows

Postby senor_cardgage » Wed Oct 24, 2012 4:45 pm UTC

He missed the obvious question that I'm sure we were all hoping would be answered:

If cows could photosynthesize, would raptors still want to eat them?

Or, what if the raptors themselves could photosynthesize? Would they still need to eat cows? Or people?

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Re: What-if 0017: Green cows

Postby mathmannix » Wed Oct 24, 2012 5:32 pm UTC

Never mind raptors, what about vegetarians? I would think that a veggie burger could be made from a green cow. Also, If one is of the "I never eat meat - except now and then a steak" variety, it would be a great excuse to say no, you haven't fallen off the wagon.
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Re: What-if 0017: Green cows

Postby Whizbang » Wed Oct 24, 2012 5:47 pm UTC

What if Vegans could photosynthasize?

Whoa...

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Re: What-if 0017: Green cows

Postby Karkasmolen » Wed Oct 24, 2012 10:18 pm UTC

I would like to point out, with unabashed smugness, that Japan was so kind as to inform me of the fact regarding cow saliva already.

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Re: What-if 0017: Green cows

Postby CoupleK » Thu Oct 25, 2012 12:29 am UTC

I liked it! Short but sweet; a nice little cap to my day.

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Re: What-if 0017: Green cows

Postby Yosarian2 » Thu Oct 25, 2012 12:42 am UTC

Mikeski wrote:They'd still need a digestive system (though maybe a lower-power one) since the cow has to be made out of something, and photosynthesis doesn't convert directly to matter, it just lets the organism build stuff out of the the water and nutrients it gets from "digesting" its environment (roots, or sometimes trapped insects like flytraps or pitcher plants).


Not quite. About 90% of the mass of a tree actually is carbon pulled directly out of the atmosphere. Water and nutrients are important, but for the most part, plants really are made out of air.

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Re: What-if 0017: Green cows

Postby Mikeski » Thu Oct 25, 2012 1:40 am UTC

Yosarian2 wrote:
Mikeski wrote:They'd still need a digestive system (though maybe a lower-power one) since the cow has to be made out of something, and photosynthesis doesn't convert directly to matter, it just lets the organism build stuff out of the the water and nutrients it gets from "digesting" its environment (roots, or sometimes trapped insects like flytraps or pitcher plants).


Not quite. About 90% of the mass of a tree actually is carbon pulled directly out of the atmosphere. Water and nutrients are important, but for the most part, plants really are made out of air.

Not quite. They're about 95% carbon and hydrogen and oxygen, and most plants don't absorb much water as water vapor. This link says most plants are 45-50% carbon by oven-dried mass, which means a live one has even less. I hate pointing to yahoo answers, but maybe about 12%? (I'm an engineer, not a biologist, so pardon the first-hits-on-google-that-aren't-global-warming-screeds references.) A thing made of 90% carbon sounds more like charcoal. :wink:

And that doesn't invalidate the cow needing a digestive system of some sort, which was the point. Pretty much all living things are 90-95% CHO and 5% "other".

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Re: What-if 0017: Green cows

Postby AvatarIII » Thu Oct 25, 2012 8:35 am UTC

mathmannix wrote:
AvatarIII wrote:
ijuin wrote: Because of this, it may be more profitable to use cold-blooded creatures (reptiles, amphibians, or shallow-water fish) as a source of photosynthesizing meat, as their metabolic energy requirements are lower (plus they won't look strange since many of them are already green!). Consider how much less you have to feed a fish kept in an aquarium as compared to a mouse of equal body mass.


Then there's the fact that reptiles are rarely if ever cultivated for food.


Wow, maybe not in the UK, but definitely in the American South. Alligator meat is considered a delicacy in cajun cooking. (I've never eaten gator, but I have eaten rattlesnake. Very greasy.) What about you Aussies? I know you have Crocodiles, I saw Crocodile Dundee...


are 'gators actually farmed though or are they hunted from the wild?


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