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#26 2019-10-29 19:38:49

SpaceNut
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Re: Mars soil good for crops

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#27 2019-10-29 20:12:50

Oldfart1939
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Re: Mars soil good for crops

If we are very smart about doing things, the soil prepared will be pre-fertilized with ammonium nitrate right in the reactor, and will come out pre-moistened and fertilized. Ready to grow plants.
One acre of land is 43,560 square feet of area, and if we simply for ease of calculations, assume 1 foot deep soil, that's 43,560 cubic feet of dirt.Divided by 27 cubic feet per cubic yard, that yields 1613 cubic yards of Mars dirt needing processed.  Taking the density of 90 pounds per cubic foot x 27, we arrive at 2430 pounds. Let's assume we can process ~2 cubic yards per reactor load, or rounding down to 4000 pounds per reactor load. In order to adequately suspend this amount of dirt, count on using 3.5 x that quantity of water. This slurry is sturred to remove perchlorate salts and centrifuged. Loaded into a second reactor and mixed with ammonium nitrate fertilizer solution. This slurry is then spread on the area where we choose to do our farming/veggie gardening.
So--what we are talking about is processing maybe 5 reactor loads per work-sol, which means during a 450 days between Hohmann transfer orbits, we can process 4500 tons of dirt, or roughly 3 acres for farming/veggie crop production.
I've made suggestions in the crops thread as to what should/could be grown.

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#28 2019-10-29 20:25:06

SpaceNut
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Re: Mars soil good for crops

Thanks for the numbers..
Sounds workable in that we will have built the greenhouse to house the volume either as small units or a larger one. Processing the dirt to use we can after its laid in place plant so we can continually grow through out the build and planting process until the greenhouse field is complete. Harvesting the crop as we go.

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#29 2019-10-29 20:39:45

Oldfart1939
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Re: Mars soil good for crops

What we will need to do is called 'intensive gardening;" my late wife experimented with this using tall vine crops (green beans, peas, wax beans) and perennial leaf crops (swiss chard), mixed in with root crops (radishes, carrots, beets, and turnips), and tubers (white potatoes, sweet potatoes). Cucumbers can be grown on trellises as can some smaller varieties of squash.

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#30 2019-10-30 02:56:12

louis
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Re: Mars soil good for crops

So just under 2000 tons of soil per acre...

But  of course you couldn't grow many crops successfully in one foot of soil. Wheat is certainly one that requires deeper soil - also true I believe of potatoes and root crops if you are going to reach Earth-like yields.  So I think the tonnage is going to be higher.


Oldfart1939 wrote:

If we are very smart about doing things, the soil prepared will be pre-fertilized with ammonium nitrate right in the reactor, and will come out pre-moistened and fertilized. Ready to grow plants.
One acre of land is 43,560 square feet of area, and if we simply for ease of calculations, assume 1 foot deep soil, that's 43,560 cubic feet of dirt.Divided by 27 cubic feet per cubic yard, that yields 1613 cubic yards of Mars dirt needing processed.  Taking the density of 90 pounds per cubic foot x 27, we arrive at 2430 pounds. Let's assume we can process ~2 cubic yards per reactor load, or rounding down to 4000 pounds per reactor load. In order to adequately suspend this amount of dirt, count on using 3.5 x that quantity of water. This slurry is sturred to remove perchlorate salts and centrifuged. Loaded into a second reactor and mixed with ammonium nitrate fertilizer solution. This slurry is then spread on the area where we choose to do our farming/veggie gardening.
So--what we are talking about is processing maybe 5 reactor loads per work-sol, which means during a 450 days between Hohmann transfer orbits, we can process 4500 tons of dirt, or roughly 3 acres for farming/veggie crop production.
I've made suggestions in the crops thread as to what should/could be grown.


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#31 2019-10-30 05:26:33

Calliban
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Re: Mars soil good for crops

I seem to remember reading that Martian dirt already contains nitrates?

To produce ammonium nitrate, ammonia reacts with nitric acid in an acid-base reaction.  According to this source, it takes about 150lb of nitrate to fertilise 1 acre of corn.  The energy cost is about the same as driving a car 650miles – about 20 gallons of gasoline, or about 50MJ/kg. 

https://www.science20.com/agricultural_ … zer-108036

So to fertilise 1 acre (4000m2), requires an energy investment of 3.3GJ.  If the average person is living on 3000m2 with 1 crop per year; that is an energy investment of 917kWh per person, or about 2.5kWh per person per day.  A colony of 1000 people would need to invest some 917MWh per year into fertiliser production – the equivalent to a continuous power output of 105kW.

Pricey.  And the reality is that we will be manufacturing on a smaller scale than Earth based industry, without the benefit of natural gas as a source of hydrogen.  So the real energy cost will be greater.  Living on Mars will be an energy hungry activity.

Last edited by Calliban (2019-10-30 05:28:09)


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#32 2019-10-30 06:24:24

tahanson43206
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Re: Mars soil good for crops

For Oldfart1939 re topic

Oldfart1939 wrote:

What we will need to do is called 'intensive gardening;" my late wife experimented with this using tall vine crops (green beans, peas, wax beans) and perennial leaf crops (swiss chard), mixed in with root crops (radishes, carrots, beets, and turnips), and tubers (white potatoes, sweet potatoes). Cucumbers can be grown on trellises as can some smaller varieties of squash.

Thank you for mentioning your late wife!

Your words inspired me overnight, with visions of what her garden might have looked like, or perhaps still does if you've had time to keep parts of it going.

I'll offer a suggestion for an activity you might undertake, if you have the time and energy, and if it seems worth while.

1) Create a new topic in the top level index "Life support systems" with the name "MarsGarden"
2) Dedicate the first post to the memory of your wife
3) Set a search term in the first post similar to:  SearchTerm:MarsGarden
4) Define the purpose of the topic so that readers can visualize an Earth based implementation of your wife's garden, except configured for Mars.
5) What this should yield is a set of emulations of a Mars Garden in schools in the UK and the US and perhaps elsewhere

The rules would be simple and understandable to students in the lower grades.

All lighting would be by LED, because the default lighting on Mars is going to be by LED.

Louis and others in this forum are enthused about natural lighting for agricultural spaces on Mars.  I think that a capability of growing crops in secure underground spaces is a prerequisite for making the commitment to send humans to Mars, or anywhere else in the Solar System.

Air can be exchanged with the outside world (on Earth) because the details of how air is prepared on Mars are outside the scope of the Mars Garden project.

Water likewise can be exchanged with the outside world (on Earth) for the same reason. 

Soil is a question.  It would be easiest to simply "import" already fertile soil into the space.  The equivalent would be to ship fertile soil to Mars, and there is an alternate future where that happens.

However, the simulated Mars soil recently discussed in this forum might be worth considering as a soil base, if it is affordable.

What is essential for any of these experiments is that records be kept.  That will be a challenge for children, so adult assistance will be necessary.

On the other hand, in a school setting, adult supervision will be present in any case, but I am talking here about volunteer support from the community, to insure that what is learned is recorded and shared via a public web site.

(th)

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#33 2019-10-30 07:56:28

Calliban
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Re: Mars soil good for crops

Growing food is a water-hungry activity.

https://www.aboutcivil.org/water-requir … crops.html

Corn requires 4000m3 per hectare per year.  Fruit crops require double this.  Even with heavy recycling, water requirements are very significant.  To irrigate 3000m2 of land to grow corn, some 1200m3 of water are required in 1 year.  That is the land we have assumed will be needed to feed just 1 person.

Recall that on Mars, water is a resource that must be mined from ice that is frozen as hard as concrete.  Most suggestions seem to focus on mining water by heat injection into buried glaciers.  The heat of fusion of ice is about 450KJ/kg.  The energy needed to heat the ice from -60C to 0C, accounts for another 120KJ/kg.  Taking into account thermal losses, we need about 1MJ of heat for every kg of water that we mine.  That is about the same embodied energy as contained in 1kg of concrete on Earth.  To mine 1200m3 of water would require 1200GJ of thermal energy.  That is 333MWh, or 40kW of heat for nearly a year, per person.

If recycling is less than perfect, then even more energy is needed to make up the losses.  If losses are as high as 10% per year, then another constant 4kw of power is needed per person to make up losses.  And recycling itself will consume energy.

One option that has been discussed on this board is the use of LED lights to grow food in compact volumes underground.  The average human needs to consume about 10MJ of food energy per day.  Assuming a generous 2% conversion efficiency of electricity into food energy; the electrical requirement to produce food for 1 person is 500MJ (140kWh) per day.  That's a continuous power requirement of nearly 6kWe per person.  To feed a thousand people would require a continuous power input of 6MWe.

Life on Mars will be an energy hungry activity and a lot of that energy needs to be in the form of heat.  You can count on needing lots of nuclear power to get this done.  A 1000 person base will need a power supply rated in the MW, just to produce enough heat for water mining.  Any rapid increase in population expands this imperative.

Last edited by Calliban (2019-10-30 08:01:03)


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#34 2019-10-30 08:13:59

Oldfart1939
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Re: Mars soil good for crops

Importation of Ammonium Nitrate from Earth would make more sense initially, than trying to have yet one more energy intensive industry in early Mars settlements. Pure Ammonium Nitrate has, in the past, been responsible for huge catastrophic explosions, so bringing it in the form of a pre-blended, general purpose fertilizer makes most sense. Remember Galveston, TX, when a freighter with a cargo of Ammonium Nitrate exploded in a blast of near Nuclear proportions; I seem to recall a date of ~ 1947.

Calliban makes an excellent observation about the energy requirements, and surplus heat from any form of energy production is a valuable commodity.

All Urine must be collected, as it contains Urea, an excellent fertilizer. Same with human fecal material. The Asian cultures have used "Night soil" for fertilizer since time of agriculture began

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#35 2019-10-30 08:14:17

GW Johnson
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Re: Mars soil good for crops

When you are living in a very cold,  dry,  frozen wasteland,  with next-to-vacuum for air pressure,  why would it be surprising that survival will be a very energy-hungry process?  I would expect the energy demand to be huge.  Even a half-dozen crew will require hundreds,  not dozens,  of KW.  Especially if they try to live off the land.  It is a VERY hostile land.

GW


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#36 2019-10-30 08:56:24

Calliban
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Re: Mars soil good for crops

Going off topic a bit: Musk is talking about establishing a city with a million people living on Mars by the end of this century.  By my estimates, such a city would need to be supported by a power supply of about 10GWe (assuming 100% capacity factor) if they are using synthetic lighting to produce food.  With polytunnel agriculture, they would need less electric power but a lot more heat.

A single large nuclear reactor here on Earth produces around 1.2GWe, with around 2.5GW of waste heat.  We would need 8 of them to feed and power a 1 million person city.  And that is without considering the need for other things, like steel, concrete, air, propellant, mining activities, etc.  If Musk is serious about colonising Mars, he needs a plan to build powerful nuclear reactors both cheaply and quickly.  A nuclear power source of 10GWe will require some 200tonnes of low enriched uranium or 50 tonnes of highly enriched uranium per year.  I would imagine the former would be more acceptable and it would appear most practical to import this from Earth.

Many of the reactor systems will need to be built on Mars, as they will be too heavy to lift from Earth.  A careful analysis will be needed to determine which systems need to be imported and which will be manufactured locally.  To avoid the need for heavy stainless steel steam generators, some sort of boiling water reactor may be most appropriate.  We can manufacture the pressure vessel on Mars from pre-stressed concrete, with an aluminium or stainless steel liner.  The high-pressure turbine can be imported.  The low pressure turbine and condenser can be made from carbon steels on Mars, with careful chemistry control of coolant water.  Control systems will be imported from Earth, as will many components like injection pumps and fuel handling machines.  We will be building reactors that are considerably more powerful than their Earth equivalent designs.  Larger reactors have better utilisation of materials and are generally more economic per unit power than smaller reactors.  And cheap is what we need.

Last edited by Calliban (2019-10-30 09:00:13)


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#37 2019-10-30 09:23:29

Oldfart1939
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Re: Mars soil good for crops

Individually, several of us have made some thermodynamic observations about different Mars settlements and relative sizes; (size determined by number of wannabe Martians). It's about time that we take the entire base as a single thermodynamic system, and calculate the hard facts about energy requirements for EVERYTHING;  not a piece here and a piece there, but everything on a spreadsheet. This will determine size of Louis' proposed Solar Array, and everyone else's Nuclear requirements. My observation, all along, is WE WILL NEED BOTH! And not one operating as an emergency backup for the other, but both operating full capacity. Here on Earth, energy consumption and availability determines standard of living. Wars are fought over such resources.

If agriculture on Mars is anything besides a fantasy, we need to be prepared to spend some significant capital making it more than a pipe dream; energy is THE KEY element.

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#38 2019-10-30 09:42:22

Oldfart1939
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Re: Mars soil good for crops

In response to tahanson43206's query about starting a MarsGarden thread: my late wife was a very good scientist in her own stead, with a chemistry degree from Case Institute of Technology in 1977. She was also the Westinghouse Award winner of the North Carolina State Science fair in 1973. So she did all the literature research on intensive gardening in a very methodical manner, and was looking to optimize CALORIC CONTENT of everything grown. She wasn't looking to grow things simply because they "tasted good," but there had to be basic nutrition in calories and vitamins present. She surmised that raised bed gardening was most efficient, and crops planted in rows used more tillable soils than those planted by broadcast of seeds. Her concept was to utilize every square foot for growing "stuff" and not having rows to walk down counted. Gardens such as these weren't particularly "pretty," but were designed for food production.

Last edited by Oldfart1939 (2019-10-30 09:43:49)

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#39 2019-10-30 09:56:04

tahanson43206
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Re: Mars soil good for crops

For Oldfart1939 re #38

Thank you for your introduction of your late wife, and for details of her interest growing nutritious vegetables.  I'm particularly interested in her work with raised beds, which certainly appear to be of interest to many in the States, based upon the catalogs I receive each spring.

I like the idea of using raised beds on Mars (or anywhere for that matter) because of the ergonomic efficiency of the system as a whole, and for many other reasons as well, which I'm hoping other forum contributors will add (hopefully with lived examples).

If you will start the proposed thread, I'll try to find at least one person in the local community who would be willing to contribute a post or two.

This forum needs to add a few more knowledgeable folks, because all the specialties that will be needed on Mars are not yet represented.

(th)

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#40 2019-10-30 10:15:12

Calliban
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Re: Mars soil good for crops

I ran a few calcs using the thin walled pressure vessel equation on how much steel we would need to produce 'cropland' on Mars.  My starting assumptions are that we would carry out agriculture in steel-framed tunnels, 2m in diameter; pressurised to 50KPa, with glass, plastic or both providing transparent panes between the steel frames.  I have assumed a carbon steel yield strength of 500MPa and a safety factor of 5.

The result: Producing 3000m2 of cropland, would require a tunnel some 1500m long.  Some 4.7m3 (36.7tonnes) of steel would be needed for the pressure resisting frames.  On Earth, new steel has an embodied energy of about 30MJ per kg.  So producing the required steel to feed one person would require some 1100GJ of energy.  That is 306MWh – or 35kW continuously for one year, per person.  Most of this would be electrical energy input to an electrical furnace and electrical input into an electrolysis cell, assuming that hydrogen is the reducing agent.  This assumes that embodied energy is the same as on Earth.  Even more embodied energy is needed for the glass between the frames and the hot water pipe that would need to run down the middle of the tunnel to keep it warm under Martian conditions.

It is easy to take for granted the free ride we get here on Earth, with abundant liquid water falling from the sky; air that we can breathe without pre-processing; temperatures that keep water liquid and abundant fossil fuels that can be burned in air to produce heat.  Without those advantages, Martian colonists look like they need 10 times more electricity per capita than comparable people living on Earth.  To enjoy similar living standards, that electrical energy would need to be 10 times cheaper, presumably.  They will need nuclear reactor designs that they can build quickly and cheaply.

https://centaurisky.blogspot.com/2017/0 … nd-it.html

Last edited by Calliban (2019-10-30 10:59:52)


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#41 2019-10-30 11:21:54

Terraformer
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Re: Mars soil good for crops

Where is water going to go, on Mars? Here on Holy Terra, it drains away into the soil and evaporates into the sky. Both of these mechanisms are going to be severely retarded in Martian greenhouses, and vary significantly here (crops in Californian semi-desert will be a lot thirstier than those in gloomy Northern England).

Crops don't need 50 kPa, fortunately. 10 kPa is enough, and reduces the stress on the greenhouse massively, at the expense of requiring workers to wear oxygen masks.


"I guarantee you that at some point, everything's going to go south on you, and you're going to say, 'This is it, this is how I end.' Now you can either accept that, or you can get to work." - Mark Watney

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#42 2019-10-30 12:22:30

GW Johnson
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Re: Mars soil good for crops

You'll need more than 10 KPa pressure,  if you expect an ordinary oxygen mask to work adequately for more than a single handful of minutes. Vented oxygen masks are inadequate for steady-state use above 40 to 45 kft altitudes,  even with 100% oxygen fed to the mask.  10 Kpa is about 52-53 kft equivalent.  40 kft equivalent is about 18 KPa.   

And don't expect to do pressure breathing without a pressure suit.  That doesn't work for more than a single handful of minutes either.  Pressure breathing requires pressure compensation.  Without it,  edema kills.  And about 0.14 bar pressure difference rips lungs,  something irretrievably fatal.

Sorry,  just the facts of high altitude (equivalent) human life support.

From what I understand,  plants will indeed grow at low air pressures,  but they also lose a lot more water in transpiration at those same low pressures.  You just raised your water consumption way up,  trying to ease the pressure shell stress problem. 

Real life is like that:  often ugly,  waiting to trip you up.  As it turns out,  that low pressure approach may not be the smart approach,  unless you just happen to have massive amounts of easy-to-obtain water available.

GW

Last edited by GW Johnson (2019-10-30 12:28:08)


GW Johnson
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#43 2019-10-30 15:15:07

RobertDyck
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Re: Mars soil good for crops

Calliban wrote:

I seem to remember reading that Martian dirt already contains nitrates?

No. Data from Mars Pathfinder, Sojourner, and Spirit/Opportunity found absolutely no nitrogen in Mars dirt what so ever. None. Geologists kept trying to find it, but found none. Curiosity has more sensitive instruments. Previous landers/rovers found nothing within their 0.1% by mass detection threshold, but Curiosity has instruments 10 times more sensitive. Did Curiosity find any nitrogen? Not that I heard, but if anyone can find an announcement of nitrogen in Mars dirt or rocks please post it.

Short answer is no.

Oldfart1939 wrote:

Importation of Ammonium Nitrate from Earth would make more sense initially, than trying to have yet one more energy intensive industry in early Mars settlements.

I respectfully disagree. Fertilizer requires so much mass that it's not worth it. Better to send equipment that can produce fertilizer from Mars atmosphere. And no, it's not that dangerous. You do have to be careful, but everything on Mars will be dangerous. Ammonium nitrate fertilizer used to be available in garden centres for use on your lawn, until the Oklahoma bombing. At one point I posted on this forum the detailed steps to make ammonium nitrate using nothing but air, water, electricity, and equipment you can buy at a hardware store. Since the Oklahoma bombing, I'm not going to post that again. Perhaps it's a good thing that post was lost with the "great crash".

Oldfart1939 wrote:

All Urine must be collected, as it contains Urea, an excellent fertilizer. Same with human fecal material. The Asian cultures have used "Night soil" for fertilizer since time of agriculture began

True. There are several groups working on this. Terry Kok was a member in the early years, his focus was on composting toilets. For a composting toilet to work, you have to be careful to not mix urine with feces. ISS currently has a toilet that collects urine with a hose, feces with a toilet astronauts sit on. Mars settlers would have to do something similar. There are composting toilets with 2 separate areas under the seat, one for urine, the other for feces. You would have to do that. Processing sewage with urine and feces mixed is far more difficult.

The GreenHab taskforce was a Mars Society group that worked on a grey water sewage processing system. Not sure what happened to them.

When I was in elementary school, one day we had a field trip to the local city sewage processing facility. It had something that looked like an Olympic size swimming pool, but you wouldn't want to swim there. Raw sewage went through that first, with steel rakes across the surface to separate out toilet paper. After the toilet paper was removed, sewage was pumped to round settling tanks. Feces settled to the bottom. Feces were scraped out periodically, taken to separate tanks called "digesters" where bacteria broke it down. The final result was called "night soil"; yes, the same word. Under government regulations (not sure whether city or provincial), that "night soil" can only be used to fertilizer crops fed to livestock. Manure from livestock can be used to fertilizer crops for people, and "night soil" can only be used to fertilizer crops for livestock. The idea is this should reduce spread of disease.

Water with urine was drawn off, taken to another step where oxygen was bubbled through in an effort to break down urea. The sewage plant had a facility that concentrated oxygen from air. Urea is CO(NH2)2, reaction with oxygen breaks it down into CO2 and ammonia: NH3. The extra hydrogen comes from water, so this turns water alkali. Ammonia dissolved in water forms ammonium: NH4+. Oxygen can react with ammonium forming water, releasing pure nitrogen. Adding a lot of oxygen to water will encourage breakdown of ammonium, releasing mostly nitrogen into the air, as little ammonia as possible. Releasing N2 instead of ammonia also makes waste water more pH neutral. Final treated waste water is released into the river. Small towns outside just use a fountain of urine to react it with air; it's really stinky when you drive past that! The city's sewage processing facility is a large industrial facility, but surrounded by residential housing, so you can imagine they go to great efforts to ensure they don't release stink into the air. But to do that the city facility has to produce pure oxygen from air, treat waste water with pure oxygen.

Treating urine to form nitrogen fertilizer requires bacteria to break it down into something plants can use. Food crops require nitrate, not urea nor ammonia. One species of bacteria breaks urea down into ammonium, another breaks ammonium into nitrite, another converts that to nitrate. So it takes several species of bacteria. There are people who know the details a lot better than me. I have suggested an idea that other experts have proposed: water plants using treated waste water. Either hydroponics or soil agriculture (I prefer soil smile ). If you use soil watered with treated waste water, the soil should be covered in plastic to ensure waste water does not evaporate into the air. A hole in the plastic for each plant. Leaves from the plant will transpire pure water into the air. Then that humidity will condense on cold windows, run down windows into a collection trough, piped to a tank. That water is potable (drinkable), and tastes a lot better than the best filtration system NASA has invented. The reason for covering soil with plastic is to ensure smell and "flavour" from waste water does not get into the condensate you collect on windows.

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#44 2019-10-31 18:07:17

SpaceNut
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Re: Mars soil good for crops

Oldfart1939 wrote:

One acre of land is 43,560 square feet of area, and if we simply for ease of calculations, assume 1 foot deep soil, that's 43,560 cubic feet of dirt. Divided by 27 cubic feet per cubic yard, that yields 1613 cubic yards of Mars dirt needing processed.  Taking the density of 90 pounds per cubic foot x 27, we arrive at 2430 pounds.

The level of water in the mars soils are in the 1 to 5% or for a cubic foot of Mars soil, you can harvest around two pints of water.
The fact that we need water for making fuel shows that if we must rely on this source we ill be processing a larger amount of soil with very little in comparison going into a greenhouse.

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#45 2019-11-30 21:00:57

SpaceNut
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Re: Mars soil good for crops

The sustanability of food growth is an issue for man even here on Earth where its going to be a hole lot easier than what we will see on mars. http://www.terradaily.com/Farm_News.html
Scientific Data, scientists surveyed the last 20 years
Researchers map food sustainability across the planet 20 indicators of food system sustainability in 97 countries -- some wealthy, some impoverished and others somewhere in between.

Scientists organized the 20 indicators -- which included measurements like greenhouse gas emissions, the presence of fair trade practices, food price volatility and food waste -- into four categories: environment, economic, social and food and nutrition.
"The food system is probably the largest employer in the world, so the sustainability of food systems is also about the economic and social contributions of those hundreds of thousands of people and enterprises that are involved in some aspect of the system -- from production all the way to food retail and distribution and consumption,"

Something that we can not ignore by shippling a constant resupply from earth and not taking a hard stance to be self reliant for the food we would wish to eat.

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