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Grex > Science > #12: The science in science fiction: Farming for Babylon 5. |  |
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russ
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The science in science fiction: Farming for Babylon 5.
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Sep 17 15:09 UTC 1996 |
So, we were talking about it. Let's look at it more closely.
The concept: How difficult would it be to "farm space" near a large
installation without its own supply of some foods, such as Babylon 5?
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russ
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response 1 of 39:
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Sep 17 15:10 UTC 1996 |
Summer Agora 129 <---> Science 12
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russ
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response 2 of 39:
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Sep 17 15:19 UTC 1996 |
An installation with a large population but little food production
would have a big surplus of what we might like to call, for lack of
a more euphonious term, fertilizer. This fertilizer contains large
amounts of essential nutrients such as potassium, calcium, phosphorus
and fixed nitrogen. Other things produced in excess as products of
metabolism are carbon dioxide and water. Miscellaneous stuff from
human activities includes salts of fatty acids (soap), cellulose
fiber in myriad forms, etc.
To such humble sludge is the bottom of the food chain anchored.
Given that this stuff will be available free or perhaps even for
a cartage fee (they pay, you haul), would it be feasible to build
a food chain ex nihilo to supply food to the parent installation?
How could this be done?
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dadroc
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response 3 of 39:
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Sep 17 16:04 UTC 1996 |
On a smaller scale you should read about ecospheres. Complete self
contained universes in glass spheres. The survive year in and year
out only needing a stable temperature and sunlight.
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janc
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response 4 of 39:
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Sep 17 16:20 UTC 1996 |
I'd say Russ is right on this one. It would be absurd to try to support a
significant population of humans for a significant time without setting up
a mostly-closed ecosystem for them to inhabit. You might as well cut their
heads from their bodies and try to support the head by some fancy life-support
machine. Perhaps feasible, but neither economically nor emotionally
satisfying. Humans are part of their ecosystem, and don't function well
without it.
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russ
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response 5 of 39:
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Sep 17 18:16 UTC 1996 |
Re #4: The premise of Babylon 5 is that some farming is done on
the station, but only for vegetables. Even eggs are imported.
This strikes me as ridiculous, so I was curious: just how hard
would it be to set up a space-farm (greenhouse, really) and turn
that sludge into "real" food?
There are 3 parts to the process, aside from transportation:
1.) Sterilize/compost/treat the sludge to get it into a form
usable by plants.
2.) Grow plants on the sludge-derived nurtient, water, CO2 and light.
3.) Feed animals on the plants, yielding flesh and eggs (and
processing wastes which feed back to step 1).
Part 1 is reasonably easy. Composting is an age-old method of killing
pathogens and producing soil from garbage. However, it's not easy to
quantify how much space or time it takes. Something like the wet-oxidation
process investigated by NASA might be better. Recipe: Take sewage. Add
a big shot of oxygen. Pressure-cook at 400 F for several hours. Produces
dissolved salts, CO2, a bit of ammonia and water.
Bactera readily convert ammonia into nitrate (2 NH3 + 4 O2 -> 2 NO3- +
2 H2O + 2 H+). Fixed nitrogen is good; it saves energy for the next
steps.
Which is conversion to plant biomass. Plants are not extremely efficient
in normal experience. However, some algae can be very prolific when fed
correctly; if memory serves, some blue-green algae in the Chlorella family
can hit 30% efficiency in converting light to energy! So something like
Chlorella growing inside glass or plastic tubes filled with CO2 and a
solution of nutrient sludge would grow like crazy.
Next step is for the next response.
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russ
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response 6 of 39:
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Sep 17 20:10 UTC 1996 |
Assume for a moment that you can get 10% conversion in practice,
so every 1000 watts of light (Is Epsilon Eridani a "sun"?) stores
100 watts of biomass-energy. A food calorie is 4184 watt-seconds of
energy, and proteins and sugars are roughly 4 calories per gram
while fats are roughly 9 calories per gram. If the algae averages
out to 6 calories/gram dry weight and the amount of light that gets
through the mirrors and windows and tubes is 1000 watts/m^2 (about
what a sunny summer day in Arizona puts on the ground), the daily
production is 1000 * 0.10 * 86400 / (4184 * 6 ) = 344 grams per
square meters per day.
The next step is feeding to animals. I've read that chickens can
produce 1 pound of weight gain from 3 pounds of grain. Assume that
feeding dried algae pellets gives half of that efficiency. 344
grams of algae would be converted to 57 grams of chicken. I have
no idea how efficient rabbits are. Shrimp and the Asian fish called
tilapia thrive on algae and are grown in small tanks or ponds, but
I have no idea how efficient they are either.
Already this isn't bad. 57 grams is about 2 ounces, so 3 square
meters of algae tank would give about 6 ounces of chicken per day,
enough for a sandwich or a nice stir-fry. If the efficiency could
be pushed to the maximum known, it could be as much as 6 times that.
An egg is what, about 2 ounces? That same 57 grams would make about
1 egg. From each square meter, every day. At maximum efficiency it
would make 6 eggs per square meter per day.
The engineering is probably easy for people who build interstellar
ships. You need mirrors and windows to get light in for the algae,
radiators to keep the temperature down, pumps and tanks to store and
move water, "nutrients", suspended algae and whatnot, and probably
spin to make a definite "floor" and "ceiling" to make chickens happy.
So, it would appear that a farm with 10,000 square meters of growing
area could turn out about 570 kilograms (about 1250 pounds) of chicken
and eggs every day, at the pessimistic efficiency. At best known
efficiency it would be 3420 kg (7500 pounds) per day. This would feed
quite a few people.
And now to the situation in the Babylon 5 story:
At black market prices, would it be long before somebody set up to sell
800 dozen eggs a day, or a half-ton-plus of chicken meat, if they could
grow it locally instead of smuggling it?
And that, I think, is where agricultural science makes the science fiction
in Babylon 5 look just a bit unrealistic.
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popcorn
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response 7 of 39:
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Sep 17 22:52 UTC 1996 |
This response has been erased.
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rcurl
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response 8 of 39:
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Sep 18 04:47 UTC 1996 |
A problem not addressed above is obtaining all of the essential amino
acids, vitamins, and minerals. The rather monotonous diet that small scale
"farming" would yield may not do so. I recall that one explanation of the
disappearance of some early culture - one of the Indian cultures of the
Southwest - was the lack of an essential amino acid in their diet.
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russ
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response 9 of 39:
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Sep 18 17:03 UTC 1996 |
Re #8: Good point. However, minerals (calcium, phosphorous, potassium
and the like) are elements and can't be destroyed. If there are few
or no losses from the system, they will be conserved. Further, while
people cannot synthesize every necessary amino acid (e.g. lysine,
which may be the one you were thinking of), plants, bacteria and
yeasts most certainly can supply everything that a chicken needs to
do it. I believe that blue-green algae are able to fix nitrogen and
synthesize amino acids, too; if something was missing from Chlorella,
it's a good bet that high-school level biology of the 23rd century
would include engineering such genes into microorganisms. It is
already a science-fair level project today.
Re #7: And that leads to another interesting factoid. Cows don't
directly digest much of what they eat; they have bacterial symbionts
which handle cellulose. I am aware that the USDA financed some
research which showed that cows could be fed on a diet consisting
almost entirely of pelletized newsprint and a bit of urea (to provide
fixed nitrogen for the bacteria's synthesis of proteins). I doubt
that goats require much if anything more. Which raises the question:
is the artificial moon of Epsilon Eridani IV made of feta cheese?
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n8nxf
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response 10 of 39:
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Sep 18 20:00 UTC 1996 |
How many pounds of beef must a person eat to gain a pound in body
mass? Then, how many pounds of vegtable material must a person eat
to gain a pound of body mass?
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russ
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response 11 of 39:
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Sep 18 20:36 UTC 1996 |
I am NOT proposing that the menu on Babylon 5 include Soylent Green. ;-)
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wolfg676
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response 12 of 39:
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Sep 19 05:19 UTC 1996 |
Re: #11- It would cut down the lurker population...
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dadroc
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response 13 of 39:
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Sep 19 14:18 UTC 1996 |
I am going to argue against composting as we know it. A bunch of research
was done after WW2 and it was found to be extremely unstable in any
industrial size. It produces pathogens that are nasty. That is why we have
liquid sewer systems. The logic is simple, no culture, no waterflow. They
wanted to shut down the chemical processes and stop pathogen production
in cases of social unrest or wars. We have done no work to explore this
problem. The data was not good, even with todays tools and 50 years of
experience.
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russ
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response 14 of 39:
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Sep 19 14:43 UTC 1996 |
Uh, excuse me? Industrial-scale composting is done in Ann Arbor for
tree leaves and yard waste, biogas reactors amount to big anaerobic
liquid-state composters (and can handle the effluent from entire
cattle feedlots), and sewage-treatment plants amount to aerobic
liquid-state composting. If that's not what you meant, I'd appreciate
you making yourself clear.
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rcurl
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response 15 of 39:
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Sep 19 17:18 UTC 1996 |
"Sludge" from waste treatment plants is rather refractory to further
bacterial decomposition or metabolism. It would have to be broken down
chemically to recycle it, which may be both time consuming and also not
yield a desirable mix of products.
Not just lysine. The "essential" amino acids, which the body cannot
synthesize, are (according to an old list I have) leucine, isoleucine,
lysine, phenylalanine, histidine, tryptophane, valine, threonine and
methionine, which are available in different proportions from different
foodstuffs. Of course, a "balanced diet" provides sufficient of all of
these. My point was that a small "food factory" cannot produce a very
large variety, and careful planning would have to go into choosing the
food products that do provide the essential amino acids in sufficient
quantity.
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russ
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response 16 of 39:
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Sep 19 17:57 UTC 1996 |
Treated sludge is sold as a soil amendment, which leads me to suspect
that it consists largely of wood fiber and the like. It burns, and
I'd wager that it would also be amenable to the wet-oxidation process.
Heavy-metal contamination is a problem in municipal sewage sludge, and
while 23rd-century bioremediation could probably handle that without
much difficulty or expense, it could be an interesting plot element;
Med Lab gets a bunch of chromium-poisoning cases because a farmer
skimped on the sludge treatment.
Meat is "complete protein" almost by definition, and Inuit used to
live on little else. It contains all the essential amino acids.
Other animals can synthesize amino acids that humans cannot, and that
is enough for the food chain.
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rcurl
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response 17 of 39:
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Sep 19 21:55 UTC 1996 |
The point is, the required processing - equipment and chemicals - is
growing, as each of these "little" impediments is addressed. The whole
thing could become too cumbersome and demanding of yet other resources,
and energy, to run at a small scale. Further to amino acids - chickens may
contain all the essential amino acids, but corn and sorghum must be
fortified with lysine, soybeans with methionine - or you have to diversity
your crops and even overproduce to meet your limiting amino acid
requirements.
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russ
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response 18 of 39:
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Sep 19 22:37 UTC 1996 |
Rane, I noted the wet-oxidation process very early on. The requirements
are few: pipe (perhaps stainless steel), a source of oxygen, and something
to heat it. The 10,000 m^2 baseline farm would have ten megawatts or so
of light falling on it. A little more mirror would suffice to supply the
required heat; if 300 C of temperature rise is required, and 20 tons/day of
slurry passes through the system, the total power required to heat it
(assuming no losses and no heat reclamation) is only another 290 kilowatts.
If the captured light is 1000 watts/m^2 after losses, that's a strip less
than 30 inches wide around the edge of a 100 by 100 meter square.
We already have high-lysine corn. Engineering Chlorella (or whatever)
to have the required nutrients ought to be a very simple proposition
250 years from now; it's already a science-fair project to tweak E. COli.
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rcurl
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response 19 of 39:
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Sep 20 03:00 UTC 1996 |
I'm losing track of the parameters of this proposition. I've jumped in
here, but I have no idea what "Babylon 5" is. Any engineering development
feasibility study depends also on the scale of the project, though the one
almost inviolable rule is that unit costs go down as scale increases *as
long as the market doesn't change*. Yes, every engineering challenge can
be "met" in some fashion, but costs, resources and "desirability" might
still limit T (which is why nuclear power is a bust). Therefore, all the
parameters within which this design is being done have to be stated.
Waste treatment by wet oxidation is used commercially. Its drawbacks
include materials of construction and the capital and energy costs of
compression - they must work at a temperature well above the critical
point. One novel way around this has been to conduct the oxidation in a
well that goes to ca. 3000 feet - it takes relatively little energy to
circulate liquid down down and up and the pressure is sufficient at the
bottom. One of these was installed out west, but it has not become popular
- or economic - because wet oxidation is incomplete, and one must still
treat the remaining organics. But it could be considered - is there
gravity at "Babylon 5"?
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rcurl
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response 20 of 39:
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Sep 20 03:15 UTC 1996 |
Oh, a plus in wet oxidation - no external heat is necessary on rich sources
as the heat of oxidation is adequate.
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janc
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response 21 of 39:
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Sep 20 04:04 UTC 1996 |
I don't follow the show very closely, but it seems to be a cylindrical space
colony, I think they said five miles long. It spins along its long axis, but
the interior seems to be more hallways and corridors than the spacious
interior of an O'Neil colony, and gravity in all the halls and corridors
seems to be uniform, so maybe they have some kind of magical artificial
gravity (I guess they do...their non-spinning space craft have gravity) so
they maybe just spin Babylon 5 for the fun of it. Population is apparantly
quite large and consists of a wide range of alien species, so your ecosystem
may have to support all sorts of aliens as well as humans. Maybe that's why
they don't grow their own food -- too complicated to support all those
different species. But humans seem to operate the place and consist of the
larger portion of the population.
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matthew
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response 22 of 39:
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Sep 20 04:40 UTC 1996 |
They spin to provide gravity (the core section of the station is extremly low
gravity) Earth ships having rotating sections to provide gravity. A couple
of the alien races have 'magic gravity technology' but most rely on rotation
or safety harnesses to keep their ships crews in place.
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void
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response 23 of 39:
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Sep 20 09:21 UTC 1996 |
re way back there: a few years ago i looked into raising my own meat
animals. it turned out that rabbits produce the most meat per pound of feed
than any other domesticated animal, but i can't currently remember the source
for that info.
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russ
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response 24 of 39:
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Sep 20 19:52 UTC 1996 |
That's fascinating, void. But is that for home farming or best commercial
practice? I'm assuming the former, and the outcome may be different.
Rane, here are the relevant specs for Babylon 5:
- Population approximately 250,000, many species represented.
Majority human.
- Construction is a number of connected spheres, like tennis
balls in a tube. There are also toroidal hallways which
have appeared in some episodes. Whether these hallways
are on the surfaces of the spheres or between them is not
obvious.
- There is at least one gardening/farming sphere where plants
are grown. There is no other farming on board.
- Due to the above, all other foodstuffs are imported, including
eggs. One episode featured a lament about not having tasted
a real egg in a long time.
- The political situation is such that travel from Earth is
restricted and goods are hard to get.
Given that, and given agricultural science known today or plausibly
inferred from current trends, my question was, is it reasonable to
use shortages of certain food items as a plot device? Given the lure
of high prices due to transportation markup, it seems unlikely that
nobody would have taken up the challenge of growing locally.
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