Scaling Agriculture on Mars

[Robotbeat]

Um, NASA most certainly CAN develop chemically-relevant Mars regolith simulant. We deal with things FAR worse than pathetic little perchlorates all the time. Heck, we use lithium perchlorate in oxygen generators.

[Aussie_Space_Nut]

I agree, it's just chemistry.

Take your Mars dirt, analyze, chemically modify to suit.

Also to a certain extent you can "make dirt" by rotting down the unused vegetation from your hydroponic systems and the waste from animals & humans.

Making lots of martian dirt will require significant effort though if the chemical modification process is hard to do.

[Impaler]

Um, NASA most certainly CAN develop chemically-relevant Mars regolith simulant. We deal with things FAR worse than pathetic little perchlorates all the time. Heck, we use lithium perchlorate in oxygen generators.

You missed the point, NASA COULD make a soil stimulant with proper levels of toxicity, but they have never done that and no one has grown a plant in anything chemically equivalent to the Martian regolith.  Martian soil contains up to 1% perchlorate, that is not 'pathetic', it is a serious issue.

All claims that plants grow in martian regolith are baseless given what they tested, it is literally pseudo-science to claim an equivalency between these soil stimulant and actual martian regolith.

[AegeanBlue]

Well, there is growth and growth. As I have repeatedly stressed soil is not necessary to grow plants. If we actually supply the nutrients chemically in the soil solution, in other words hydroponics, our soil requirements are far fewer than if we try to create a living soil medium. With hydroponics what we mostly care about are the mechanical properties of soil. We also care if there are chemical interactions between the nutrients and the soil components, but not so much as with true soil. With true soil we need to colonize a biosphere on the Martian regolith. The experiments on growing on Martian soil simulant so far have been of the second category, attempting to create a biosphere. The message seems consistent: we can do it if we add dead plant material. Also they have taken place on Earth where the member of the soil biota are ubiquitous, if there has ever been an experiment where the Mars simulant was in biohazard style isolation to sequester it from earth's biosphere please let me know. Considering the huge variety of soils on Earth, I am pretty sure that we can identify many Martian soils that are relatively friendly to bacterial colonization. But, as I said, I am more of a friend of hydroponics.

[Robotbeat]

Um, NASA most certainly CAN develop chemically-relevant Mars regolith simulant. We deal with things FAR worse than pathetic little perchlorates all the time. Heck, we use lithium perchlorate in oxygen generators.

You missed the point, NASA COULD make a soil stimulant with proper levels of toxicity, but they have never done that and no one has grown a plant in anything chemically equivalent to the Martian regolith.  Martian soil contains up to 1% perchlorate, that is not 'pathetic', it is a serious issue.

All claims that plants grow in martian regolith are baseless given what they tested, it is literally pseudo-science to claim an equivalency between these soil stimulant and actual martian regolith.

You know what else is pseudoscience? The claim that all Martian regolith contains these levels of perchlorates.

[Impaler]

Your deflecting now with straw-man arguments.  I've shown quite clearly that Martian soil stimulants lack the known toxic chemicals found on Mars, trying to claim we will find some uncontaminated regolith is unsupported and illogical considering the wind blown dust on Mars.

[the_other_Doug]

Your deflecting now with straw-man arguments.  I've shown quite clearly that Martian soil stimulants lack the known toxic chemicals found on Mars, trying to claim we will find some uncontaminated regolith is unsupported and illogical considering the wind blown dust on Mars.

The wind-blown dust isn't highly concentrated with perchlorates, AIUI.  The dust is mostly bits of oxidized ferrous basalt, with a somewhat surprisingly large admixture of carbonate materials.  The perchlorates all came to be via chemical reactions in acidic and chlorine-rich groundwater, which didn't tend to chemically alter the surface rocks as much as it altered the soils and buried soil strata.  And it's been the surface rocks that have eroded into the ubiquitous dust far more than the soil layers which were most strongly altered.

And, as has actually been correctly pointed out, not all areas of the planet were inundated with chlorine-rich water.  Many of the Meridiani Planum units Opportunity has studied are chlorine-poor but rich in other evaporitically-emplaced constituents, like bromine and sulfur.  And finally, not all chlorine-rich units developed the exact right chemistry to create perchlorates.

So, the point is not a strawman.  There are likely large areas of Mars with little to no perchlorate enrichment in the soils.  And when the levels are low, soils can be treated to remove the offending chemicals.  All Martian soils will be treated in a variety of ways before they are used to grow food crops regardless -- removing or transforming perchlorates and other trace toxic chemicals will be a routine part of that soil treatment.

[RonM]

I wouldn't worry about perchlorates in the soil. Obviously, any agriculture will have to be done in a pressurized structure and not an open field. If Mars farmers went to the trouble of creating soil, it would have to be watered by an irrigation system, so they might as well use hydroponics and forget about creating soil.

[JasonAW3]

I wouldn't worry about perchlorates in the soil. Obviously, any agriculture will have to be done in a pressurized structure and not an open field. If Mars farmers went to the trouble of creating soil, it would have to be watered by an irrigation system, so they might as well use hydroponics and forget about creating soil.

Actually, you might be better off using aeroponics.  Lower amount of actual water needed to grow the vegetables.

[Robotbeat]

I wouldn't worry about perchlorates in the soil. Obviously, any agriculture will have to be done in a pressurized structure and not an open field. If Mars farmers went to the trouble of creating soil, it would have to be watered by an irrigation system, so they might as well use hydroponics and forget about creating soil.

Agreed. I personally think we'll be doing hydroponics to supplement microalgae staples (and other single celled foods).

Besides the fact that there are most certainly going to be some soils of Mars that lack high perchlorates, perchlorate removal is pretty easy. To get rid of perchlorates, you just need to rinse the soil. If you're feeling especially clever, you may be able to even exothermically evolve oxygen out of the perchlorates (using a catalyst) while you wash out the soil.

But yeah, I think most calories will be grown initially from single-celled food sources (and then highly processed) with supplement from hydroponics.

[LMT]

ZLD: Water, Dirt, Salt

All Martian soils will be treated in a variety of ways before they are used to grow food crops regardless -- removing or transforming perchlorates and other trace toxic chemicals will be a routine part of that soil treatment.

Makes sense, yes.  And Zero Liquid Discharge (ZLD) tech seems suitable. 



Remarkable abilities:  ZLD plants cleanse wastewater streams far nastier than martian rinsewater, producing clean water and, notably, a variety of fertilizing salts. 

All automated and energy-efficient.  Plus ZLD steam can feed efficient electrolysis, for gas products.

A ZLD MCT suggests itself as a hub of colony infrastructure.

To get rid of perchlorates, you just need to rinse the soil. If you're feeling especially clever, you may be able to even exothermically evolve oxygen out of the perchlorates (using a catalyst) while you wash out the soil.

Right, washing it out as a first step, as with soluble contaminants generally. 

And below -7000 m, on summer days the relatively high pressure and temperature allow you to rinse the soil in open air.  Outdoor wash - no pressure facility required.  That helps.

Re: perchlorates:  I understand commercial ZLD plants remove perchlorates from wastewater by inserting an electrodialysis stack into the treatment chain.

I wouldn't worry about perchlorates in the soil. Obviously, any agriculture will have to be done in a pressurized structure and not an open field. If Mars farmers went to the trouble of creating soil, it would have to be watered by an irrigation system, so they might as well use hydroponics and forget about creating soil.

Well, ZLD seems necessary for water treatment, no matter how the garden is constructed. 

Plus open-air rinsing of regolith / global unit would feed contaminants into ZLD, for transformation into fertilizer - much needed for gardening.
 
So it seems clean water, clean soil, and fertilizer can be produced in a fairly straightforward ZLD scheme. 

So the question is:  why not garden conventionally?

[oldAtlas_Eguy]

Plants are sensitive to soil PH levels. Wrong chemicals at wrong concentration levels make a soil toxic  to plants. Even if they still need those chemicals but at very different concentrations. Earth soil has been self created and plants adapted to what is here to match plants and soil. The martian soil will need adjustments to match to plants needs. Removing and adding chemicals/minerals.

A ZLD could be used just to extract fertilizer materials with the processed soil basically dumped back to the surface since the inert soil is not required.

[LMT]

pH, Fertilizer, Rocks and Aquaponics

Plants are sensitive to soil PH levels. Wrong chemicals at wrong concentration levels make a soil toxic  to plants. Even if they still need those chemicals but at very different concentrations. Earth soil has been self created and plants adapted to what is here to match plants and soil. The martian soil will need adjustments to match to plants needs. Removing and adding chemicals/minerals.

And that's one of the reasons to tweak the fertilizer mix: to adjust pH, right?  If you start with cleaned sand, your initial soil is circum-neutral.  pH would therefore be under your control.  For example I understand alteration of the urea / ammonium nitrate ratio will readily change pH.  These fertilizers would be sourced from the ECLSS / gas plant, and other fertilizers from the ZLD plant, all under control, so I don't know what stokes the pH concern.  Some particular regolith mineral, or just the unknowns?

A ZLD could be used just to extract fertilizer materials with the processed soil basically dumped back to the surface since the inert soil is not required.

Well, technically, gardening with cleaned, inert sand is a kind of hydroponics, at least initially.  If sand does nothing else, it anchors and orients things conveniently, yes?

Of course, organic matter would accumulate on the grains in time, to transition the plots into more conventional gardening.  But it seems you're advocating growth in mineral solution, solo, without inert medium.  If the required labor and difficulties of this hydroponic or aeroponic gardening could be made comparable to those of conventional gardening, then yes, I suppose you could dump.

Question:  Those of you who've tried your hand at solution-only hydroponics or aeroponics, how does the labor / difficulty of these methods compare with conventional gardening?

Related Question:  I wonder, are there relevant quantitative yield results published for combined solution-only hydroponics and aquaculture?  That is, "aquaponics" - raising fish, prawns, etc. between/beneath the floating roots of hydroponic crops.  Conceivably aquaponics could increase yield.  For example it might improve on my aquaculture yield estimation of 8800 meat calories per square meter per Mars year, by augmenting the meat calories with useful plant calories.

Hypothetical example:  In imitation of coastal paddy/fish culture, a salt-tolerant rice, such as the Oryza coarctata / IR56 hybrid, is introduced into the aquaculture.  Aquaponic nutrients are added, which presumably the fish and prawns tolerate.  The rice leverages the aquaculture's supplemental LED lighting, which enables year-round plantings.  The rice grows entirely above the fish and shrimp in floating, gas-permeable, transparent hydroponic trays or meshes. 

Hypothetically, the scheme works.  The rice gives perhaps 3000 calories per square meter per Mars year, increasing the system's total yield to about 12,000 calories per square meter per Mars year.

Very hypothetically.  And of course the yield increase would have to be weighed against any increase in labor or difficulty, to justify.

[Paul451]

These fertilizers would be sourced from the ECLSS / gas plant, and other fertilizers from the ZLD plant, all under control,

This is the ZLD plant being described in the video you posted:



And it does not separate out the components in the concentrated waste. It produces a water stream, and a wet pile of mixed crystallised salts.

In order to separate the components of the gas-plant and especially regolith wash-water into controlled fractions, you need a chemical refinery. And then for each separate output stream, you need a separate ZLD plant to get the water back. (Actually, you'd want a much more elaborate ZLD-type system, because water won't be the only component you want back. ZLDs vent their gases, whereas you want to isolate/separate and concentrate the different gases as much as you do the different salts.)



There's a tendency for people to "solve problems" by compounding the number of major industrial processes they want to hand-wave into existence, without any regard for the mass and complexity of the systems they want (even ignoring the added complexity of Mars ops compared to the much simpler Earth-based equivalents.)

Would it really be easier to import/assemble/operate/maintain a complex chemical refinery on Mars than to just import some fertiliser on the regular shipments from Earth?

[guckyfan]

There are interesting operational facilites which combine aquaculture for fish with tomatoes and other vegetables. Water is fully cycled.

That rice design is interesting too, but I doubt that staple crops will be grown on Mars in large quantities. Most calories will come from algae IMO. Need to figure out how to produce viable flour from algae carbo hydrates, but that should be doable. A californian company offering a variety of foods for vegans has algae flour for baking in their product range.

[LMT]

ZLD

[ZLD] does not separate out the components in the concentrated waste. It produces a water stream, and a wet pile of mixed crystallised salts...  And then for each separate output stream, you need a separate ZLD plant to get the water back.

Brine is recycled through the same crystallizer, to precipitate fertilizing salts in sequence. 

General sequencing for precipitation of fertilizing salts from ZLD brine:

1.  Fe via oxidation & pH increase

2.  Mg via pH increase

3.  Ca & P via pH decrease, then alkaline agent

4.  K via temperature decrease

One crystallizer in one ZLD plant producing multiple fertilizers.  That would be convenient, yes?

you'd want a much more elaborate ZLD-type system, because... you want to isolate/separate and concentrate the different gases...

ZLD is wastewater treatment, not a gas plant.  It could feed steam to the gas plant, for electrolysis, but I don't know what other gases you'd want from the brine itself.  What other gases are you trying to obtain from brine, and why?

...just import some fertiliser...

Micronutrients fit on a pallet, but consider the bulk fertilizer requirement of 9 acres of intensive gardening, as in the Lake Matthew scheme's initial self-sufficiency garden for 100, augmented with hypothetical rice aquaponics.  That initial 9 acres might consume 20 tons of bulk fertilizer per Mars year.  If the fertilizer is imported by MCT, that's perhaps $100m of fertilizer, just for Year One. 

Fertilizer for scale-out to the scheme's full 70+ acres of greenhouse space would exceed the capacity of an MCT, pushing fertilizer cost toward $1 billion at scale-out.  Thereafter nutrient losses through waste would force shipment of additional fertilizer each synod, maybe some tens of tons --

unless there were an efficient way to process wastewater for fertilizer recovery.

And this, in roundabout way, makes another case for inclusion of ZLD fertilizer tech in a colonial infrastructure.

[AegeanBlue]

Generally you do not want to remove nutrient salts from the water just to add them again later as salts. N, P, K you keep in the solution. Na, Cl, you remove ASAP. The rest is more of the issue of managing pH and sediment, if the water has too much Ca and CO3, you will see CaCO3 form and clog the emitters. Also availability of micronutrients depends on the pH, hence the need to constantly buffer it.

Generally hydroponics has very small labor demands. You set up the irrigation schedule in the automation, you set up the solutions for the injectors and off you go. Then afterwards some disaster strikes, e.g. some emitters get clogged, and EVERYBODY is scurrying to fix the issue before the whole crop is lost. But generally routine operations require very little labor.

ZLD sound like a nice idea, though I am not sure about the practicality. Industrial wastewater tends to be high load - low volume while agricultural wastewater (with significant exceptions, e.g. olive mill wastewater) tends to be low load - high volume. We will need to clean the dirty water on Mars, although with the exception of the first washing loads for the substrate loads will be low, but the salts removed most likely not be sufficient for fertilization. We need to put out there ammonia plants for N fertilizer and mine appropriate P and K rocks, we will not be getting these fertilizers from cleaning brine. Also the wastewater produced by the colony, either by the people or the irrigation drainage, will have high organic loads rather than the typical mineral loads produced by industrial wastewater for which ZLD is designed. We usually clean organic loads through biological treatment, like the wastewater plants treating your sewage. Biological treatment takes less energy than ZLD. I am also unaware is ZLD is optimized for high organic loads, though I am sure that GE can convert it so.

In all honesty though let's see what will be the actual water source in the colony. If we are constantly removing brine from an aquifer, ZLD is necessary. If we are recycling clean water, not so much

[LMT]

Field Experience

Generally hydroponics has very small labor demands. You set up the irrigation schedule in the automation, you set up the solutions for the injectors and off you go. Then afterwards some disaster strikes, e.g. some emitters get clogged, and EVERYBODY is scurrying to fix the issue before the whole crop is lost. But generally routine operations require very little labor.

It's interesting experience.  Was it hydroponics with or without inert planting medium?

Which crops did you grow? 

And subjectively, how did the total end-to-end labor (including rig build) compare to the labor expended on similar crops in conventional gardens, at that scale?

P.S.  Do you think that aquaponic scheme with rice, tilapia and prawn could work, and with the productivity imagined?  Or do you see some big problems there?  I ask because that aquaculture has the highest productivity I could see, just ballparking from the literature and working with plant and animal species commonly judged tasty.

[Paul451]

ZLD

[ZLD] does not separate out the components in the concentrated waste. It produces a water stream, and a wet pile of mixed crystallised salts...  And then for each separate output stream, you need a separate ZLD plant to get the water back.

Brine is recycled through the same crystallizer, to precipitate fertilizing salts in sequence. 

No. You are making that claim. The patent you linked to doesn't. (It involved multiple separate stages, each with their inputs (acids, alkalis, oxidisers, etc) and processing tanks/filters/pumps/etc. But it ends with the separation of the bitterns (mixed salts from brine evaporation) using some kind of crystallising evaporator. In essence, a single step in the process (System 78) is the entire ZLD system, just to produce the final mixed salt. It doesn't talk about separating out that bittern salt into its individual components. Nor do the prior metal-extracting stages use common systems or common processes.)

[mikelepage]

Question:  Those of you who've tried your hand at solution-only hydroponics or aeroponics, how does the labor / difficulty of these methods compare with conventional gardening?

Related Question:  I wonder, are there relevant quantitative yield results for combined solution-only hydroponics and aquaculture?  That is, "aquaponics" - raising fish, prawns, etc. between/beneath the floating roots of hydroponic crops.  Conceivably aquaponics could increase yield.  For example it might improve on my aquaculture yield estimation of 8800 meat calories per square meter per Mars year, by augmenting the meat calories with useful plant calories.

Hypothetical example:  In imitation of coastal paddy/fish culture, a salt-tolerant rice, such as the Oryza coarctata / IR56 hybrid, is introduced into the aquaculture.  Aquaponic nutrients are added, which presumably the fish and prawns tolerate.  The rice leverages the aquaculture's supplemental LED lighting, which enables year-round plantings.  The rice grows entirely above the fish and shrimp in floating, gas-permeable, transparent hydroponic trays or meshes. 

Hypothetically, the scheme works.  The rice gives perhaps 3000 calories per square meter per Mars year, increasing the system's total yield to about 12,000 calories per square meter per Mars year.

Very hypothetically.  And of course the yield increase would have to be weighed against any increase in labor or difficulty, to justify.

The principles of aquaponics are being used there - but that kind of set up is more difficult to control/maintain - and I wouldn't want people to think aquaponics need be that messy.  For the vast majority of plants you want a separate grow bed containing clay media that host bacteria/invertebrates that would normally be in soil - you use the clay media so that the water doesn't get mucked up by dirt.  Also, by having the pot above the tank, and having the water drain back into the tank it helps oxygenate the water for the fish. 

I've had two small aquaponics rigs over the last 4 years, and I've found them to be very low ongoing labour.  Once you get them to equilibria, they maintain themselves to a large extent because you're just replicating the nitrogen cycle.

The first one I've heard called "aquariponics", I literally just put a 12L rectangular pot on top of my 18L fish tank and powered it with a $22 pump on a timer switch.  I used nothing I couldn't buy from the local hardware store.  Cost me about $300 all up.  4 gold fish, and was growing aloe vera, coriander & mint for about 2 and a half years (might have cleaned the tank 5 times lol), before this fungal outbreak appeared out of nowhere and killed the lot.  Cest la vie. (It's this experience that has given me to the opinion that any Mars mission would want to have 3+ redundant/isolated AP systems for safety).



I didn't try to restart the first rig because by that stage I had set up my second rig (2 years old now and I've cleaned it twice), and probably spent $1k on it so far because it's in our front entertainment/al fresco area and it's supposed to look nice.  600-700L tank with 5 pots = 60-70L grow space.  Currently got 5 young citrus trees (lemon, lime mandarin, orange, cumquat) which aren't fruiting much yet, but I think they'll get there with time.  I also have mint in the pots now, which (like all herbs) is great at sucking up any excess nitrogen.  Powered by large cichlids (basically bigger goldfish) which have shown a lot more tolerance to occasional temperatures down to 15 degrees C.  I first tried barramundi but here outdoors in Perth it gets too cold for them- they died off pretty quickly, and it's super expensive to heat the tanks all the time.  Had a few algae outbreaks before we bought a UV filter which solved that problem.

The most positive aspect of this set up is that the cichlids have been breeding, so obviously we've managed to get the system into a good equilibria without doing all that much work.



I will go larger when I eventually do my third rig, and try growing edible fish once more.  The benefit of size is that once you get up to volumes >1000L water it tends to hold it's own temperature a lot better rather than my current rig, which follows the temp curve of the day.  I'd also like to close the fish food part of the loop by setting up compost/worms - so veggie scraps go into the worm farm - which feeds the fish - which produce ammonia for the nitrogen fixing bacteria in the clay ball media - which produce nitrate fertiliser for the plants - which produce food for us.

To be honest it's a complete no-brainer to me that Mars/space settlements will incorporate principles of aquaponics/permaculture into the system.  I'm sure initial food stuffs will be shipped from earth, or algae based, but in this age of super-sized farms producing hundreds of tons of food per day it's easy to forget that farming can scale down quite nicely to quantities that would suit an initial Mars settlement sized food production.  You just have to make allowances for the needs of the system. 

As far as trying to estimate actual quantities of food produced per mass AP systems go, the local AP shop here sells "starter" rigs (which are a 1000L tank + 1000L grow bed) as "producing food for a family of 4", which I don't believe for a second, but I think if that was the allowance (2 ton) for every single person, it might be enough to completely supply dietary needs.