How much volume does a liquefied human take?

Question

A group of aliens are off to save the human race from extinction caused by a Lovecraftian monstrosity.

In order to accomplish this feat, they go to Earth in order to harvest as many humans as possible to restart the race while keeping as much diversity in the gene pool as possible.

The thing is, the aliens don't have time to introduce themselves and have the humans sort themselves out. So they arrive one day and start abducting people for the greater good. In order to store the humans they have acquired, they liquefy them in-order to save...how much space on their craft exactly?

I would like to know how much volume a liquefied person takes up if they were stored in the most spatially-economical vessel (a cube or rectangle, though cylinders might be needed if under pressure.)

The age groups I would like are:

• Toddlers

• Teenagers

• Adults

(Don't question how they are liquefied only to come back normally afterwards. We are dealing with Clarketech here.)

Answer 1

How good is liquefaction?

L.Dutch's answer is the right concept, but his numbers are wrong. 6 liters is the maximum inhalation of an average adult male; however, men have much larger capacity than women and normal respiration does not fully inflate the lungs. The 62 liter volume of an average adult assumes a resting inhalation volume which actually averages closer to 2.5 liters of air in your lungs (during normal at-rest breathing across genders). Volumes of gastro intestinal gases vary a lot throughout the day, but average about 1 liter. This means his equation should look more like 3.5/(62+3.5) = 5%; so, you only get a 5% reduction in absolute volume.

That said, the more important savings are in removing the empty spaces around the body. An average human is 160x39x23cm that is 143.52 liters. When you compare that to the 58.5 liter liquid state of a human, you get 143.52/(143.52+58.5) = 71%; so, your reduction in practical volume would be 71% compared to shoving us in boxes.

This will result in the following:

Age Group          | Avg. Whole Weight | Avg. Volume
-----------------------------------------------------
2yr old Toddler      12,000 g            11,100 cm^3*  
13yr old Teenager    45,000 g            41,600 cm^3*
Adult                62,000 g            58,500 cm^3

*Due to lack of data, child volumes are based on mathematical ratios compared to adults.
Different childhood ratios of bone, muscles, organs, etc might impact these figures. 

Designing the packaging:

To package your humans this way, place thier remains in large plastic bags kind of like IV bags. This will keep your remains separate, sterile, and waste very little space.

That said, because some fluids such as stomach acid would react with other fluids such as brain chunks, you may in fact want to store certain biological substances separately rather than in on big bag to make sure you still have all the same compounds coming out as you had going in. This may mean a complex system of "disassembling" the human body into separate bags rather than just throwing them into a blender. This can lead to some unexpected wasted space as you start needing to account lots of total bag materials, air gaps between bags, and possibly wasted space in whatever bins you use to keep all the liquid human sacs organized in. It's hard to say just how much space will be wasted without delving REALLY deep into human biochemistry and industrial design to determine how many bags and of what size you need; so, lets just say it will still be more efficient than boxing whole humans, but maybe closer to a 50-60% savings if you go this rought.

But, your aliens could do better

Generally I agree with Carl's assessment that you don't need to bring whole people, but cloning humans requires large artificial wombs, and lot of labor for your aliens to hang around baby sitting us for 20 years waiting for us to have a functional adult population while our DNA synthesizes all the complex compounds (proteins, fats, nucleic acids, carbohydrates, etc.) that make up an adult.

Instead of a slurry which is 60% water, you could dehydrate the human pulp into a "meat and bone meal". This is an industrial term referring to the dehydrated and ground up remains of an animal. Since any planet they are bringing us to would inevitably contain lots of water, they would just need to rehydrate our remains as part of the reconstitution process using the water from our new world. https://en.wikipedia.org/wiki/Meat_and_bone_meal says that meat and bone meal averages 4–7% water; so, if you reduce the human body from 60% water to 4-7%, you are eliminating about 57-58% of a human's total mass.

According to calcert.com, loose meat and bone meal is has a density of 0.72 g/cm^3. This is a bit less than our liquid density because the powder will have room for air, but will still have a lower total volume than liquid humans while allowing the aliens to transport all of our complex compounds needed to put us back together.

This will result in the following:

Age Group          | Avg. Whole Weight | Avg. Dry Weight | Avg. Volume
-----------------------------------------------------------------------
2yr old Toddler      12,000 g                5,100 g        7,080 cm^3*  
13yr old Teenager    45,000 g               19,125 g       26,560 cm^3* 
Adult                62,000 g               26,350 g       36,600 cm^3*

*Due to lack of data, meat and bone meal density is based on animal meal.  Human meal 
might be slightly more or less dense.

If the remains are vacuum sealed like coffee, you could increase the density of your meal to be just a bit over 1 g/cm^3; however, vacuums cause most organic compounds to break down; so, depending on how advanced your alien tech is will determine how much they can safely compress your human remains.

Going back to the practical volume of a human, this means you will get about an 82% practical reduction in volume by converting people to meat and bone meal. If you opt for liquefaction in your story, I would suggest giving some brief handwave explanation for why you can not dehydrate the human remains.

Designing the packaging:

Another possible advantage to removing water from the human body is that it makes freezing us far less destructive. Water expands when freezing which plays havoc on on the other molecules being frozen with it. The Arrhenius equation shows that as things cool, things that react at higher temperatures stop reacting with one another. This means you can deep freeze stomach acid and dehydrated brain chunks together without them reacting with one another such that you can get an even better efficiency out of your packaging by keeping us in one very cold container.

Even under low-vacuum states, vacuum sealed plastic and foil cubes are probably the best way to store and separate human remains because they maintain a sterile, light weight, easily stored, separate vessel for each human, and can be shaped into cubes for optimal space efficiency. To figure out how big these cubes have to be we should look at the top end of who the aliens might select for transport. If they want to save the species, they will probably select people based on health factors meaning the obese and dangerously tall may be excluded. This puts a reasonable upper limit of 115kg on your whole weight. If we assume a light vacuum seal will compress the meal density to about 0.85 g/cm^3, then we get a finished volume of about 41,055cm^3 or a cube that is about 35x35x35cm.

If it were me, I would describe the human storage room as being a cryogenically cooled cargo bay full of pallets of vacuum sealed blocks, all ~35x35cm at the base so that they stack nicely, but ranging from ~4-35cm tall. By mixing and matching people of various volumes, each pallet could be filled to the maximum height recommended by alien freight regulations.

In conclusion:

There are many factors that could play into how you could and should store a disintegrated human, and it all boils down to "how destroyed is too destroyed to reassemble." Hopefully this goes into enough (though be it disturbing) detail to figure out how compressed your humans should be.

Answer 2

The average volume of an adult human is about 62 liters.

Assuming that the aliens don't use any process that causes the loss of volatiles elements, the only saving from liquefying a human body would come from the air volume taken by the lungs and bowels.

In an average adult the lungs account for about 6 liters of air, while the bowels I wasn't able to find accurate values, so I would go for the same volume as the lungs.

That would save about $12/(62+12)=16\%$ of the volume taken by a normal body.

Since we are at it, the same page I linked above calculates the volume of entire mankind is about half a cubic kilometer

If you stacked everyone together into a Human Cube (hmmm, I should trademark that), it would be about 770 meters on a side.

Since the average above covers adults, teenagers and toddlers, I won't go into further calculations.

Answer 3

Since we know that the density of a human is very close to 1kg/l (we float in water, but only just), a human’s volume in litres is pretty much the same as their weight in kilogrammes.

Answer 4

The whole concept is wrong. If you want to save the species and the diversity of the species all you need is a couple bottles full of cryogenically stored eggs and sperm. And a decent artificial womb, but if they can travel from wherever to Earth, that shouldn't be a big problem.

Resurrecting actual people is a huge waste of mass and effort, and further it'll be a lot easier to acclimatize newborns to the alien planet than to try to get native Earth-born folk to adjust.

Answer 5

Liquification won't be all that effective. Basically, you reduce the problem to "what is the volume of a human being?"

One can find this volume via Archimedes' principle. Fill a tub with water, put the human in the tub, letting the water spill over, and measure how much water left the tub. However, we can do this faster. The human body is roughly the same density as water. Thus, for every kg of human, you have roughly 1 liter of water. Get any growth chart of your preference, and you find out how many liters they are (in particular, toddlers grow freaking fast, so there's no one number).

Now if these aliens mean business, they need to then put the liquid in a dehydrator, to concentrate the humans. Orange juice concentrate gets about a factor of 4 size reduction (which is why you add 3 cans of water to bring it back). The human body is only about 60% water, but you should be able to squeeze a bit more out of it!

Freeze dried humans are probably the most effective form of packaging. It works for ice cream!

Answer 6

How much volume does a liquefied human take?

Just over 1 litre per kg of mass.
Close packed in a rectangular sided form (cubes or other).

Because:

Rather than looking at materials, lets look at some attributes of "real people".
The average person will float in fresh water with air in their lings and will usually sink if all air is expelled.

The density of fresh water is 1 kg per litre.
So the density of "just sinking" people is just over 1 kg/litre.

If you allow 1 lite per kg = 1 cubic metre per tonne (or ton) in rectangular sided shapes you get a slightly higher than absolutely minimal volume.
Add whatever allowances you need for storage (shelves, protection, ... . )

Most of the body is liquid which is incompressible.
If the technology allows you may gain a little more packing density by compressing no fluid materials.

Answer 7

It really depends on the pressure, because liquids are, contrary to common belief, compressible, it just takes much more pressure than gases. In fact, everything is compressible, even the most incomprehensible thing there is, a neutron star, can develop into a black hole.

So, I say, for maximum compressiblility, the minimum volume occupied by the liquefied people is only dependent on the mass, and is a sphere with radius r = 2GM/c², where G is the gravitational constant, M is the mass, and c is the speed of light (this is the Schwarzschild radius), which is very small for the whole population of Earth. Subatomic, in fact.

People compactified into black holes should not lose their original information, according to the outcome of a bet between Stephen Hawking and Leonard Susskind, so the aliens may be able, in principle, to reconstruct the people from the information in the black hole.

Answer 8

What you want is a justification for liquifying the human body. Since some answers have already pointed out, the act of liquefying itself is useless, I will try pointing some other things

If you only want to save volume and not mass why not make them denser?

Why not extract only the nervous system and then liquefy it? Wouldn’t that make them more self-righteous...

In absence of logic the reasoning you choose can be arbitrary. If you are hell-bent on liquefaction to save humanity from galactic extinctionists go with the second soln.