No external fish food?

[Eric T]

Is it possible to have a completely internal system, where all the fish food is generated by the aquaponic system itself?  I know that sounds like a "perpetual energy machine", but the sun is ultimately the engine for everything.  Could algae be grown in the tilapia pond, and duckweed in one of the grow beds, and then all vegetable waste (stems, leaves, etc) could be fodder for the BSF?  Would that be enough, or is some external fish food necessary?  Thanks for your help on this.

[Eric Warwick]

In addition to pee. Pee is not enough in a closed system.
TCLynx said:

Eric W, so why would chemical nitrogen fertilizer be more sustainable than an immediately available local nitrogen source like say (pee)?

[Eric Warwick]

(Not sure if the reply went through) I do think that local N will be available for a long time, but over the long run a well managed N extraction from the air and rock will  be important. As I see it sustainability means a really long time, because of the conservation of matter.

TCLynx said:

Eric W, so why would chemical nitrogen fertilizer be more sustainable than an immediately available local nitrogen source like say (pee)?

Eric T,

The really big benefit to growing with aquaponics is the water savings.  If you don't want to eat the fish, you could do some other form of bio-ponics.  (Pee ponics for instance.)

[Laine Houberg]

I suppose in theory it would be possible to combine a worm composting element to an AP system and fuel it with your own organic garbage. If you include yourself as part of the system it may work as a closed system, just a thought. Makes for a decent existential question at least.

[Eric Warwick]

Yes, that would be highly efficient, but some sort of matter input is needed for it to work. In Florida they have that (see African Dust).

Laine Houberg said:

I suppose in theory it would be possible to combine a worm composting element to an AP system and fuel it with your own organic garbage. If you include yourself as part of the system it may work as a closed system, just a thought. Makes for a decent existential question at least.

[TCLynx]

But you were talking about using a chemical Nitrogen source.  Pee provides plenty of nitrogen, yes you might need other nutrients but they can often be provided by things like wood ashes or if using the pee as the nitrogen source for composting of heavy carbon organic matter.

You plant legumes with their symbiotic bacteria to extract nitrogen from the air.

So I don't see how using fossil fuel derived chemical nitrogen fertilizer would be more sustainable than using our own "waste" products instead of flushing them away in hopes that some one else can render them non pollutants instead.

[Eric Warwick]

The legumes don't produce enough. That's the problem. Yes, pee will provide N, but at a strict fundamental level it won't provide enough in a closed system. Granted the type of sustainability I'm talking about is more than just 7 generations. The chemicals I'm talking about is things like Chilean Saltpeter or Sodium Nitrate. If managed properly, and all wastes are accounted for, would provide an ultimate sustainability, until we have to use up N2 in the atmosphere. This would take millions of years though. Just in a closed system some sort of input is necessary, that's what I was getting at.  

TCLynx said:

But you were talking about using a chemical Nitrogen source.  Pee provides plenty of nitrogen, yes you might need other nutrients but they can often be provided by things like wood ashes or if using the pee as the nitrogen source for composting of heavy carbon organic matter.

You plant legumes with their symbiotic bacteria to extract nitrogen from the air.

So I don't see how using fossil fuel derived chemical nitrogen fertilizer would be more sustainable than using our own "waste" products instead of flushing them away in hopes that some one else can render them non pollutants instead.

[Laine Houberg]

African dust that blows over the atlantic ? Im not sure I see what you mean.

Eric Warwick said:

Yes, that would be highly efficient, but some sort of matter input is needed for it to work. In Florida they have that (see African Dust).

Laine Houberg said:

I suppose in theory it would be possible to combine a worm composting element to an AP system and fuel it with your own organic garbage. If you include yourself as part of the system it may work as a closed system, just a thought. Makes for a decent existential question at least.

[TCLynx]

Eric, I think you lost me.  What scale of a closed system are you talking about?  People survived and farmed for generations without needing sodium nitrate or saltpeter by composting the manure from themselves and their animals.  It is only since we opened the nutrient cycle and started putting our own manure where it could be nothing but a pollutant that organic sources of nitrogen haven't been enough.

Eric Warwick said:

The legumes don't produce enough. That's the problem. Yes, pee will provide N, but at a strict fundamental level it won't provide enough in a closed system. Granted the type of sustainability I'm talking about is more than just 7 generations. The chemicals I'm talking about is things like Chilean Saltpeter or Sodium Nitrate. If managed properly, and all wastes are accounted for, would provide an ultimate sustainability, until we have to use up N2 in the atmosphere. This would take millions of years though. Just in a closed system some sort of input is necessary, that's what I was getting at.  

[Eric T]

Pee-ponics, very intriguing!  I've been reading TCLynx's postings about this, it seems like if you just let pH raise to > 9 then it's safe (if not taking any drugs).  Eric W. suggests it doesn't supply enough NPK and trace elements.  Since there would be no fish, could one add to the water stuff (soil, compost tea, etc) that would otherwise harm fish, but would be okay for plants, to supply these missing elements?

Also, I'd be very interested, TCLynx and Eric W, if you could briefly lay out, schematically, what a  closed system (full ecosystem) would consist of, how much land is required, both for fish-eaters (aquaponics) and vegans (pee-ponics).

Thanks, enjoying this discussion.

[TCLynx]

I've never tried to live in a terrarium so I don't know how big it would have to be to be a completely closed eco system.  Bio-sphere is pretty big though and they were only able to do it for brief periods of time.

To be self sufficient "ish" Well ya gotta define how self sufficient you need to be to call it a closed system?  I don't think most of us are quite up to manufacturing our own solar panels and batteries and mining our own metals to make wiring to operate our AP systems off grid and even fewer people are really dedicated enough to go out to their AP systems every hour to bucket or hand pump the water up to flood the beds to do it without power.  And since I don't know anyone who has been willing to do that much, I can't really say how much land/space you would need to also manage manufacturing your own fish feed as well as all your own food with AP and permaculture. 

Now I have read about a guy who has eaten nothing but what he could grow organically on about 4000 square feet of garden, apparently he was really skinny and grew lots of potato.

[Vlad Jovanovic]

Eric W, 

You kind of lost me too? Barring the millions of years time scale bit...

Why would pee not provide at least enough N, but 'a couple of fish' can?... Need more N, add more fish... need more N add more pee. Urine (human) having an NPK value between 11-1-2 to 15-1-2 ...I'd be more worried about N build-up than not enough.

I'm with TC on the sustainability factor. Urine or petroleum based fertilizer (or, saltpeter mined from the earth)? Millions of dollars in equipment to (sometimes rather haphazardly) drill it out of the Earth, then a ridiculously complex and very costly/energy intensive process to process it vs. YOU JUST PEEING IN A BOTTLE!?! (how's that for the 'ultimate in sustainability' :)   The other things mentioned like wood ash seem preferably more sane as well, especially if you are already heating your home with wood (like I and others already do.)

I really believe that what I've been doing on a small scale might work with something larger. Worm tea/hummonia/wood ash for my NPK, and MaxiCrop (or equivalent) for trace elements. (Though the castings I'm sure provide many TE's as well. NPK value of worm castings will vary, but 5-5-5 would be at the higher end of the scale).

[Alexandre Letellier]

Interesting thread, I like the idea of using the minimum input, especially if they are industrial/chemical.

Speaking of which, Vlad, I think you mentioned rusty nails in another discussion. Can that compensate for the iron deficiency in AP ? Rust is iron 3 oxide, is it transformed into iron sulfate or chelate by bacterias or some other processes in the system ?