The iAVs Promise – the Detail
The iAVs Promise – the Detail
The iAVs promise reads…..
iAVs has the capacity to produce fish and fresh vegetables sufficient to provide a family with 200 kg of fish and 1,400 kg of vegetables (fruit) per year in a footprint equal to an automobile parking space. *
*Assumes a sub-tropical or temperate climate or controlled environment that will permit year-round plant production.
That’s a bold claim and one that should be quantified…so here’s the detail.
(click image to enlarge)
The use of this comparative scale was initially proposed by Dr. H. Douglas Gross, Professor Emeritus of Crop Science at North Carolina State University (NCSU) and former Assistant Director of International Programs. It was anticipated that this approach would be easily understood and valued by AID (Agency for International Development) officials. However, this assumption proved to be incorrect. Despite this, we remain hopeful that you will recognize the potential of small-scale, low-tech iAVs.
Context here is Lo-tech, such as for LDC, ‘Third World’ application. Yield from Moderate- to Hi-tech iAVs (e.g., with powered aeration, protection/shelter, CO2 amendment, Etc.) can be from 2 to 3 times greater per unit area/time than indicated here.
The following calculations are based on an area of 3.5 meters by 8 meters, resulting in a total surface area of 28 square meters, which is approximately equivalent to the size of a standard parking space.
Of this area, 18 to 20 square meters is used for the bio-filter/grow bed. Premised on 4 tomato plants per square meter grown as single-stems at 3 crops per year = 234± plants per year. With 234 plants each producing 6 kg of fruit = 1,404 kg yr-1.
When cultivating tomatoes, or other similarly vertical and lengthy crops, growers can optimize space during the early growth stages (approximately the first month) by intercropping with short-duration crops. This technique allows for the simultaneous production of fast-growing species, such as various greens and herbs, which can be harvested up to three times per year. These crops serve as an ‘understory’ to the primary crop, utilizing available space and light more efficiently. By selecting compatible species, growers can enhance overall productivity through this complementary planting strategy.
The fish production is premised on 40 to 50 kg m-3 yr-1 depending on feed quality, temperature, DO levels, harvested size, and other factors. The tank would occupy about 4 to 5 square meters with a volume from 4 to 6 cubic meters.
Yield of 200 ±50 kg LW Tilapia per year at a typical market size (in much of Africa) of 250 to 300 gram LW each. This harvest size may be achieved in from 100 to 120 days from the 15 g fingerling stage.
Harvesting either as batches (cohorts) several times per year or as individuals selected daily/weekly (as desired), or in some combination of household use and cash market sales or barter.
If (when) operated without access to electrical power, the remaining area (2 to 5 m2) would be used for a cascade-aeration ‘ladder’ sited between the filter’s outlet and the tank. With electric power, the remaining area may be used to increase the grow bed area and/or tank volume.
Please notice that I have not claimed that this is the most practical configuration, rather it is what could be fit into the given area.
iAVs will produce more food, faster and do so using FAR less water (and energy) than any other method of food production with a comparable capacity.
-o0o-
Thanks for the links Mark
Thanks Mark, we have indeed come up against all of the problems you mention. We installed a UVI-style module in a poor semi-urban neighborhood about 6 months ago. There have been some hiccups but no fish kills or any major problems so far. We are only about an hour away so we are able to stop by every once in a while to answer questions that come up. I am sure the system would not be doing well if we weren’t in the area. We only use tilapia here due to the warm climate. I disagree with your last statement, I find most failed projects (my own or other’s) teach extremely valuable lessons. What sort of pumping system did you use in your projects in Africa?
Some examples, there are surely many more:
In the Sahel, other than by calabash, the closest examples I could find were like these but had a circular flywheel handle for smoother turning
http://www.franklin-electric.co.za/media/10836/Orbit-HOP-leaflet.pdf
other examples http://www.waterafrica.net/Water.htm
http://old.hydromissions.com/products.htm#pumps
I also saw bicycle (pedal, chain and sprocket) driven types in use, as are various ingenious animal-powered rotary drives
Nation-wide projects intended for Namibia (not implemented, ‘blame’ USAID) were to use solar pumping provided by Siemens
Mark, I am interested in evaluating the possibility of implementations where there is no electrical service, situations where the cost of the pump (and backup) would severely limit the scope of the project, and areas where the electrical service is often intermittent. Why do you ask? Any advice you would like to share from your work in Africa?
I’ve asked because I want to understand which direction you were possibly headed. I also want to repeat that the ‘parking lot’ illustration is not presented as I would literally suggest.
What species of fish are you factoring? With relatively low DO levels and warm water, TMK tilapia is basically the only viable choice.
I could hypothesize at length about experiences in Africa but don’t have the time and also see that as largely irrelevant. I was operating without a backstop or support, without an understanding of local cultures/dialects, and in very different times. The only thing relevant I can think of is do NOT expect people without grounding/knowledge in any of the sciences to understand such things as pH, ppm, DO sat., or what a molecule, anion, cation, even flow rates etc. are. Explain the basics as simply as possible even if the explanation isn’t strictly accurate. Even simple terms that you and I may take for granted such as ‘biomass’, stocking density, ratios, yield rate, etc. may not be understood by those not steeped in aquaculture. Also, just because someone may indicate that they have understood what you’ve meant/said does not actually mean that they have. Further, since I had no actual influence or enduring effect, I’m next to the last person you’d want to solicit advise from. Not intended as criticism or a treatise.
In the “parking space” plan there appear to be access aisles on top of the sand area, is this the case? Can you walk on the sand without causing some kind of adverse compaction effect?
Yes, rows spaced for interior crop access. Suggest placing planks or stepping stones to walk on so as to not disturb sand surface. Sand won’t compact per se but it will form indentations and ridges ( no longer be smooth if walked on).
David, I want to pointed out (emphasis) “Please notice that I have not claimed that this is the most practical configuration, rather it is what could be fit into the given area.” In other words, this is not ‘exactly’ the most practical approach. Are you considering implementations where there is no electrical service available?
Ok. I see what you mean. I confused “saturation” with water’s DO level. Excellent. Thanks for clearing that up. 🙂
The “Sand versus Gravel article as a Biofilter” mentions the sand allows “maximum aqueous dissolved Oxygen (DO) saturation possible”. Do this mean sand is sufficient in giving maximum DO saturation possible?
If above is true… Why must there be a “cascade-aeration ‘ladder’ sited between the filter’s outlet and the tank” when no electricity is involved?
Love the iAVS. I am just confused about the necessity of some mechanical aspects due to the given explanations.
The phrase you cited is from this statement (aka fact) – “Vastly increased effective aeration of the media benefiting both soil bacteria/community activity and the plant roots’ assimilation rate – with 25,000 times (or more) greater concentration of molecular Oxygen (O2) than the maximum aqueous dissolved Oxygen (DO) saturation possible.” Reread “greater … than …”. Sand does NOT increase DO levels. Sand does increase O2 availability for the bacteria and plants (when irrigation and drainage recommendations are adhered to).