Friday, January 19 2024

Bio-polymer Production: A critical technology for Off-world Colonization

Reliable production of plastic films and fibers will be crucial to many, many other aspects of the colony, including nutricyling, food production, synthesis of medicines and other useful chemicals, and construction of habitats. The following is a brief rundown of a few promising options.

fermentationtanks.png, Jan 2024

Polyhydroxybutyrate (PHB) is a well-known and very promising bioplastic. Many species of bacteria (especially Bacillus cereus) can produce it with zero genetic modification or artificial selection. It is produced as granules inside the cytoplasm, with stress having the potential to increase this production to a significant percentage of their weight (30-50%).

I believe that by lysing the cells in a standard blender (or perhaps by freezing) and then centrifuging, these granules would likely separate into a visible layer and be easily extracted from the rest of the cell matter. Either as part of this extraction step, or for forming/3D printing, the granules could also be dissolved in chloroform or acetic acid. The latter would be preferable as it's easier to produce biologically and not as toxic, but both are fairly simple.

PHB will likely need plasticizers mixed in to improve its flexibility and decrease brittleness, either as a film or as a 3D printed part. Vegetable oil (easily derived from crops or from algae) is one option, as is glycerol. Glycerol is a byproduct of the standard production of biodiesel from plant oils (The reaction of the oil along sodium hydroxide in a methanol solution), so might happen to be available if the colony used/produced biodiesel.

Polylactic acid is another well-known bioplastic, and one that's used even now in conventional 3D printers. Lactobacillus spp. are bacteria which naturally produce lactic acid during anaerobic digestion of carbohydrates. This includes sugars, more complex starches, and potentially even raw cellulose if it's pre-digested by other enzymes or chemical processes beforehand (e.g. alkalis similar to the process for creating wood pulp).

The bacteria and feedstock can be filtered from the solution, and the lactic acid precipitated out by the addition of calcium carbonate. This reacts to produce calcium lactate salts, and carbon dioxide. The calcium lactate is insoluble, and so drops out of solution and can be easily collected. The calcium lactate can be treated with dilute sulfuric acid (5%) to make calcium sulfate (insoluble) and lactic acid, so it's comparatively easy to separate a pure product. Sulfuric acid could be produced from the sulfur byproduct of a biodigester, though calcium carbonate is more difficult and regenerating it from the calcium sulfate is a challenging proposition. Potentially different bases could be used to precipitate out the lactic acid, which are more amenable to regeneration/continuing cycling.

After a purified lactic acid monomer is obtained, it must be polymerized into the polylactic acid. I believe the best approach is a direct polycondensation. A ‘ring opening’ polymerization is also possible after conversion of lactic acid to the diester lactide, but this is more complex and provides a lower molecular weight product. Direct polycondensation requires low temperatures in a dehydrating environment along with constant mixing and agitation, though temperatures must also be high enough to melt the PLA. One approach would be to use digital temperature control alongside a magnetic stirbar and a vaccuum pump. This removes water from the solution, gradually shifting the reaction equilibrium towards high molecular weight PLA. The higher the temperature, the more the diester lactide ring is formed as a byproduct, lowering final molecular weight and reducing yield slightly. 180*C is the approximate ideal.

Optionally, there is also solid-state polycondensation (SSP). After carrying out the above steps briefly, the PLA can be allowed to cool and solidify around 20-25*C below its melting point. At this point it is solid, but still capable of continuing the polycondensation reaction, increasing its molecular weight, sometimes by orders of magnitude. This is a long process however, often taking multiple days even with metal or metal salt catalysts (Sn, Zn). Perhaps it would be a necessary part of the manufacture, or would only be used when high molecular weights (causing higher density, greater strength, etc.) is necessary.

Rough protein/cellulose films are another option. Agricultural waste or any other product with cellulose and protein content can be treated with a number of simple acids and then pressed into shape, yielding a film with only low permeability to water and air. Formic acid (the simplest organic acid) could be used, and would be relatively simple to manufacture either by direct microbial synthesis or partial oxidation of methane into methanol, and then formic acid. This could be an option for low-stress, non-critical areas, such as flooring or containers for growing terrestrial plants, open storage containers, furniture, etc.

Nanocellulose is a highly promising material as well. Bacteria cellulose can be produced quickly, inexpensively, and yields a very pure product, even if other sources of cellulose (wood pulp, flax/hemp fibers) are unavailable. Though the current partial-oxidation used to produce nanoscale features on treated cellulose uses a complex aminoxyl radical (TEMPO), some researchers have had excellent luck using only nitric acid in conjunction with sodium nitrite. Nitric acid and sodium nitrite are readily produced from atmospheric nitrogen through N-fixing and N-oxidizing microbes.

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Psychological/sociological maintenance

Extreme environmental conditions naturally mean that most time must be spent indoors. Limited resources mean that 'indoors' will probably be fairly small. Food may end up being rather spartan--enough to live on, but not necessarily delicious or particularly varied. Spending all your time in a small room with the same few people, eating mediocre food...sounds like a recipe for depression and short tempers.
This topic is for discussion of how to deal with that. Methods for maintaining positive mental attitudes, keeping up energy levels, and preventing lethargy are all welcome.

Initial ideas include
-Some level of privacy/enough spaces
If you've just had a disagreement with a fellow colonist, being able to move away and cool down before talking to them again could be the difference between a shouting match and a productive resolution. Each colonist should ideally be able to have a private space of their own to decompress and relax.

-Mentally-engaging physical exercise
Exercise is naturally very positive for mental stability and health. However, things like treadmills, exercise bikes, or resistance bands can be hard to commit to regularly. Finding a way to make these mentally-engaging and fun as well would provide a mental boost and synergize with the physical exertion to further improve mood. Some kind of game like those old Wii Fit minigames, maybe VR?

-Decrease sense of enclosure
Even in extreme environments, being able to go outside will be very important to prevent a sense of claustrophobia. Maintaining excursion suits and planning for regular trips to scenic spots outside of normal work should be a priority. Maybe outdoor sports of some kind could be included, along the lines of the previous bullet?

-Make the indoors pleasant
If you're going to be spending almost all your time inside, it should be a pleasant space. Potted plants might seem silly, but seeds/rhizomes can be packed very small and could make a big difference to the 'feel' of a space. Design of interiors should be planned carefully, and coloring interior walls should be considered.
Maybe some kind of artificial sun lamp , or the use of mirrored surfaces to make a space feel bigger than it is?

All other ideas accepted and welcome.

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Interesting article about just this subject
Here are some excerpts

For the most part, the typical psychological problems you'd find in space are no different from what you'd find in a high-stress environment here on the surface. They include:

difficulty sleeping


mood lability

feelings of discouragement

heightened nervousness or anxiety

A nurse working in the E.R. or a long distance runner training for a marathon might experience these kinds of symptoms pretty regularly. But when an astronaut — who is trained more rigorously to withstand stressors — starts to experience these kinds of symptoms, there's a much larger cause for concern, since they're essentially trapped up there in space.

Beven says these problems are not unlike what you might find for someone who is unfamiliar to a long winter in a northern country, or a prisoner who is placed in solitary confinement.
The other facet is what Beven calls behavioral support: it's essentially the way he and his team make sure an astronaut has access to hobbies or forms of entertainment that they can indulge in in their leisure time to unwind and de-stress. It could range from music, to watching sporting events or television, having access to games — whatever. Even astronauts love to watch Game of Thrones, and it's critical to keeping their sanity.

"Our belief is that if you're forced for six months or more to live and work in your office, the downtime really needs to be rejuvenating," says Beven.
as space travel begins to expand — both in allowing more people access to space travel, and in sending more people out to greater distances beyond Earth's orbit — aerospace psychology will need to change. "In the next 10, 20, or even 50 years, how are we going to provide the system to allow the first Mars crew the same opportunities for psychological support that the ISS crew has — even if there is a 45-minute delay in communications?" asks Beven.

One idea: using A.I. programs to that can provide instant cognitive behavioral therapy to astronauts onboard a spacecraft or working on a Martian or lunar colony. A future astronaut may be having bi-weekly meetings with an artificial robot on their iPad, instead of chatting so frequently with a human being here on Earth. "I don't think anything on Earth right now has been proven to work in that realm, but that's something we need to make certain is working," says Beven.

And as spaceflight becomes commercialized and low-Earth orbit operations are turned over to private companies, it's unlikely commercial astronauts will be as rigorously screened as NASA's astronauts are right now. Beven predicts "there will be someone who does have the first psychotic episode in space," or the first manic episode, or someone who develops a drug or alcohol problem in space.
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Plant Microbial Fuel Cell

This system could potentially also generate electricity, using a system called a Plant Microbial Fuel Cell

biofuelcell.png, Jan 2024 «Microbial solar cells: applying photosynthetic and electrochemically active organisms. Trends in Biotechnology.»

Power densities are quite low, a few dozen milliwats per square meter, but it's nearly 'free' in terms of resource cost since the biodigester and algal tanks are already planned for. That might help offset electricity use if artificial lights weren't in use, and would be a very stable and resilient source for a few watt-hours.

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NASA Water Walls

NASA research concepts were touching on a similar idea some time ago! With the added refinements of making the system modular, and using it for radiation protection

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From here
The lungs of our planet – the forests, grasslands, marshes, and oceans – revitalize our atmosphere, clean our water, process our wastes, and grow our food by mechanically PASSIVE methods. Nature uses no compressors, evaporators, lithium hydroxide canisters, oxygen candles, or urine processors. For very long-term operation as in an interplanetary spacecraft, space station, or lunar/planetary base, these active electro-mechanical systems tend to be failure prone because the continuous duty cycles make maintenance difficult and redundant systems to allow downtime bulky, expensive, and heavy. In comparison, Nature's passive systems operate using biological and chemical processes that do not depend upon machines and provide sufficient, redundant cells that the failure of one or a few is not a problem.

WATER WALLS (WW) takes an analogous approach to providing a life support system that is biologically and chemically passive, using mechanical systems only for plumbing to pump fluids such as gray water from the source to the point of processing. The core processing technology of Water Walls is FORWARD OSMOSIS (FO). Each cell of the WW system consists of a polyethylene bag or tank with one or more FO membranes to provide the chemical processing of waste. WW provides four principal functions of processing cells in four different types plus the common function of radiation shielding:

Gray water processing for urine and wash water,
Black water processing for solid waste,
Air processing for CO2 removal and O2 revitalization,
Food growth using green algae, and
Provide radiation protection to the crew habitat (all cells).

Although chemically and biologically different, these cells are physically similar in size and shape, so they can be physically integrated into the WW system. With this cellular and modular approachWW system is designed to be highly reliable by being massively redundant. As part of the spacecraft design, the replaceable cells and modules are installed in the structural matrix. Before departure, they are primed with water and starter ion solutions. As one cell for each function is used up, it is turned off; the next one is turned on by opening valves to admit the appropriate fluids. The spacecraft carries backup FO bags and/or membranes. The crew can replace exhausted cells with new units. In this concept, WW can replace much of the conventional mechanically-driven life support that is so failure-prone with a reliable system that also affords "non-parasitic" radiation shielding and can grow basic protein and carbohydrates to sustain the crew over multi-year missions.

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Nutricycling--turning waste into food

This is a general summary of a 'first draft' concept for using biological systems to turn waste products into food. It's not the be-all end-all, and I'd absolutely appreciate input from others on ways to improve it.

Nutricycling.jpg, Jan 2024

The basic idea is to use a 'biodigester' as the first part of this process. To simplify, when you put high-nitrogen wastes into an anaerobic environment, certain types of bacteria will begin to break them down for energy. As a byproduct of this process, they also produce methane, hydrogen sulfide, a liquid effluent rich in nutrients, and a solid 'slurry' of material more resistant to digestion.

The gaseous methane and hydrogen sulfide can be tapped off with a simple airlock like the types used in brewing. When this gas is bubbled through an aqueous culture of Halobacillus purple sulfur bacteria, they partially oxidize the hydrogen sulfide into elemental sulfur, which precipitates out of solution and can be later collected. The methane can then be safely combusted for energy generation, or even fed into a fuel cell.

The liquid effluent is rich in nutrients, but needs further treatment. If thoroughly aerated, the remaining bacteria in the solution mineralize these nutrients, changing them into a form much more readily absorbed by plants. This nutrient solution can then be sterilized by heating or ultraviolet light, and its pH and EC adjusted if necessary. Once this is done, it could be used effectively in hydroponic style soilless cultivation of plants. In the diagram, I've indicated an algaculture growing two common species of protein-rich, calorie-rich, nutrient-rich species of algae. Algae grow much more rapidly than terrestrial photosynthesizers, and require a lower intensity of lighting, making them an excellent choice for maximizing food production per unit area per unit time. Theoretically, a human's daily caloric needs could be met by 1.5lbs (~700 grams) of spirulina algae. Calories would be ~30% from fat, ~15% from carbohydrates, and ~55% from protein.
However, algaculture will likely not be able to provide for all a colonist's nutritional needs. Vitamin B12 could be supplied by oyster or white button mushrooms exposed to UV lamps, and a small area of hydroponic vegetables like garlic, kale, spinach, or others for variety and mineral content.

The solid slurry left over could be dealt with in a number of ways. I personally favor the use of a colony of omnivorous insects, perhaps Eublaberus distanti (six-spotted cockroach) or Hermetia Illucens (black soldier fly). Both species reproduce rapidly, are tolerant of crowding, and are largely indifferent to the quality of their food so long as it is organic in nature. Their digestive process would change the slurry into forms more accessible to the microbes of the biodigester, so the cockroaches' frass (and the cockroaches themselves, after humane dispatch) could be shredded and re-introduced. If the cockroaches could be cleaned and processed, they might even serve as an additional food source. Alternatively, any insects could be fed to domesticated fowl or fish, and these secondary consumers used for food.
The solid slurry could also be composted in a more traditional fashion, if their carbon:nitrogen ratio could be adequately balanced with additional materials.

It should be noted that this generalized system is likely to be fairly intensive in its use of electricity. The biodigester itself, the sterilization unit, and the insect colony will all need to be kept around 80-90*F. The hydroponic gardens will potentially require artificial lighting, to the order of 22,000 watts per colonist for 8-12 hours a day depending on light spectrum and efficiency. Pumps for aeration and transport of nutrient solution will draw some current as well.
Methods for producing this electricity, reducing demand, or other workarounds would be greatly appreciated.

image_007.png, Jan 2024