Sorry ’bout the lateness of this ‘Happenings’…but life just got in the way this week.
A New Waste Transformation Farm Project
In my spare time, I provide consultancy to aspiring waste transformation (WTF) farmers. It’s not very lucrative because I haven’t charged for my time but it does allow me to extend my reach into regions that are dissimilar to my own place…thereby expanding the WTF knowledge base.
Anyway, it looks like I might be working with the owner to adapt an existing small cattle farm to the waste transformation method.
Ebb and Flow Hydroponics System
I divided my collection of about eight kangkong plants into lots of root sections and planted them out into the ebb and flow unit. This unit is now outside (rather than in the shadehouse) so, with the recent mild weather. I’m hoping we’ll have lots of little plants on their way.
There’s been a significant change in our situation during the past week…and we didn’t have to do anything at all.
Our neighbours on our northern boundary removed several very large trees in preparation for house-building. In so doing, they brought about a big change in our solar exposure.
The removal of the trees directly impacts us in three ways.
First, we no longer get the shade provided by the trees and, in a world that is getting hotter, that’s a downside.
The second impact – an upside – is that parts of our place that were previously in shade, are now growing areas. And that clears the way for the remaining impact…we’re now have the location and capacity for solar panels.
The trees will be missed. The decision to remove one should never be taken lightly and we’re sad that they’re gone.
But, now we have to make the best of what we’ve got…and that’s a going to be a recurring theme for all of us…on a personal and global level.
I spent much of this past week thinking about this project and why, although the build is almost complete, nothing was happening.
I’m so close that all I had to do is finish the sump tank installation and connect the pipework from the fish tanks and filtration modules to the sand biofilters and DWC grow tanks…but, with only a few hours of work to do, I felt incapable of making the final effort.
And then I came to the realisation that the premise that underpins my comparison project is no less flawed than the research methodology that inspired it.
The first research trial, conducted at the American University in Cairo (AUC) by Hisham El Essawy sought to establish which method (iAVs or DWC) was the better choice for Egypt – given its circumstances. While the methodology was flawed, this trial concluded that iAVs was the more effective growing method for Egypt.
The second trial, conducted (also at AUC) by Lobna Salem, sought to establish whether deep water culture (DWC) or sand beds were the better way to grow lettuce. While the methodology for this trial was also suspect, it concluded that DWC was the better method for growing lettuce.
Upon reflection, I concluded that my iAVs/DWC comparison was simply going to confirm the findings of the first trial. On the matter of the second trial, I came to the conclusion that knowing how to grow one type of food plant to the exclusion of all others, was actually of little interest to me.
I also realised that by continuing with the comparison, I was going to lock myself into a regime of water testing, filter-cleaning and external nutrient mineralisation (or supplementation) that DWC requires but that iAVs does not.
I was, in effect, going to devote a whole heap of time and effort to confirm what Mark McMurtry proved over 30 years ago…that, all things considered, iAVs is the most productive, resilient and sustainable way to grow plants using the metabolic wastes of fish.
The other more disturbing realisation was that, even if I’d done all of the work that was necessary, it would actually have done little to change minds. I’ve observed throughout my 14 years of association with aquaponics that people act on what they believe rather than that which is verifiable fact.
So, given all of that, I’m not proceeding with the comparison.
Now that I’ve freed myself from that yoke, I plan to take the project in a different direction.
I will now commission the iAVs as soon as I tidy up the few remaining build tasks and arrange for the purchase of some fish.
One of the questions that I encounter, from time to time, is…”Could I connect a DWC tank to an iAVs?” I propose to answer that question as soon as I satisfy my initial curiosity about my new toy.
After that, I’ll probably source some more sand and convert the DWC tank to another sand biofilter…and possibly even a second discrete iAVs with its own fish tank.
There are so many questions that remain to be answered about the method but my first inclination is to determine whether there’s any discernible difference between glass sand and the quartz silica stuff.
So, that’s it…until next week. Take it easy!
Let me introduce you to Rob Greenfield. He’s an interesting man for a number of reasons but it’s actually his home that interests me right now.
Why do we spend 25 – 40 years of our life energy putting a roof over our heads when we could have a mortgage-free tiny house?
I’m sure that there are people out there who feel that they couldn’t live in anything less than four bedrooms, two bathrooms and a 3 car garage but, to me, this is what liberation architecture is all about.
This project was the big winner this week.
I straightened up the leaning pier on the iAVs bed…
…and drilled the holes for the flange fittings…before lining the beds with the local equivalent of Duraskrim.
The flange fittings were bolted into place.
The DWC tank drain was straightforward enough…that’s a simple standpipe arrangement. The iAVs drain was rather more complicated – in this particular application. It features a section of slotted agriculture drain pipe covered in a fine mesh sock to provide for effective drainage while ensuring that the sand stays in place.
And then I waved my magic wand and 1.5 metric tons of sand moved itself into the iAVs bed. I secured the liner edges with some pine battens to finish off the sand biofilter and DWC grow tank.
The sand that I obtained for this project is not ‘sand’ as we’d normally think of it…it’s glass sand.
I used it because it satisfied the criteria for iAVs sand…it’s inert, free of silt and clay and it’s particle size range is such that it will drain very well. It was given to me so the only cost was for the transport from the mainland to our island…a mere $80.00. That it’s made from recycled bottles is a nice little sustainability bonus.
That’s it for next week so, until next week, keep growing – and take it easy.
Apprenticeship in Lifestyle Development
This project hogged the time, this week…but the outcomes more than justified the effort.
To recap, I’ve begun to teach my grandsons the things that the education system won’t teach them…achieving happiness through simple living and self-reliance. While most grandfathers probably teach their grandchildren useful things, my approach will be a little more intensive…and goal-directed.
We spent the week learning simple tasks like ropework and knots…caring for chickens…roughing out blanks on a wood lathe – and various other micro-masteries. This was largely about learning to learn for them…and us getting used to each other in our adjusted roles.
They returned to their mainland home on Saturday – and voted the fortnight a huge success.
While I completed the structural elements of the grow bed/tank last week, the ground under one of the cement block piers has settled to the point where the pier now a slight Leaning Tower of Pisa feel about it.
It’s probably not a big deal – but these beds will weigh in excess of a metric ton once they’re filled – so I want to be absolutely certain that they’re safe to be around. The other issue is that every time I walk past them, I’ll know that one of the piers has a slant on it…and that will annoy the hell of out me. So, I’ll fix the problem before I line the beds and install the drains.
Our twelve chickens laid twelve eggs – last Friday – for the first time. While this wouldn’t normally be noteworthy, it was huge for me after months of fluctuating egg production.
While it’s been a really busy week, there’s been limited progress on the project front. I’m hopeful that this situation will change in the coming week. We’ll see.
Until then, take it easy.
I completed the sand bio-filter – and the DWC grow tank – this week.
Both growbeds/tanks are made from treated pine sleepers – 2.4m x 1.2m x 400mm deep. These structures are supported on cement blocks. I used more treated pine sleepers to distribute the weight on the blocks. Each bed will weigh over a metric ton when filled with media and water.
A sheet of 19mm formply completes the structural aspect of the growbeds. I should point out that I tend to over-engineer things…but this was also probably the most cost-effective way to accommodate my circumstances.
My next task is to install the drains in the growbed and tank.
New Ebb and Flow system
This system has had no end of incarnations. It was a worm farm, then a quail breeder pen, then an ebb and flow hydroponics seedling propagator, then a worm farm again…and, this week, it’s back to being an ebb and flow hydro system again. I filled the grow bed with expanded clay pebbles and hooked up a pump and timer. I planted a bunch of leggy pak choi seedlings – just to get things growing.
Currently, this unit (and my other hydroponics systems) are running on packaged nutrients. It’s a two-part dry powder mix…and each part is mixed with water to produce 20 litres of nutrient solution. It’s easy to use, cost-effective and entirely predictable in terms of its growing performance. It’s still my plan to use nutrients that are sourced from organics but, until I get that sorted out, the packaged stuff will suffice.
IBC Test Bed system
I have a love/hate relationship with IBC’s
The IBC basic flood and drain system…and it’s retarded little brother, the ‘chop and flip’ system…are to be found in their thousands in backyards throughout the world. They are usually slightly oblong in shape and are constructed in such a way that it is generally difficult to concentrate and remove particulate wastes. They are, therefore, a poor choice for use as a fish tank. They are also party to what fate has done to the iAVs system…and, for that, I’m not a fan.
As a systems freak, however, I’m fascinated by IBC’s…so this project is about exploring some of the ways in which they can be used in waste transformation farming.
Currently, these IBC components are serving as water storage and two duckweed tanks. That will change within the coming weeks as I begin to showcase the range of uses to which these vessels can be put.
Mega Bin duckweed unit
Mega bins are very useful containers for micro-farming. My short term plan is to grow duckweed in these two bins.
Apprenticeship in Lifestyle Development
I have my two grandsons (11 and 13 years respectively) visiting with me for the school holidays. Both are fairly typical products of the education system which parrots the societal mantra…”Do as you’re told. Study hard in school. Get a good job. Be Happy.”
Intertwined with all of that is the “Great Australian Dream” of buying one’s own home (over a period of 25 – 40 years) – for which one spend the best years of one’s life working to provide shelter for oneself.
We delude ourselves into thinking that if we do these things, we’ll have made it…but those who cannot achieve this ‘blissful’ state are deemed failures.
I believe that the education system exists for two reasons…to produce compliant workers – and to self-perpetuate.
I’ve long been aware that, if this nonsense works for anyone, they are few in number. It certainly didn’t work for me. What I achieved in life was in spite of the education system rather than because of it.
After considerable thought, I’ve decided to ‘apprentice’ my grandsons. The indenture is not a formal trade…like building, engineering or cookery. It’s an Apprenticeship in Lifestyle Development.
It seeks to provide them with the knowledge, skills and experience to chart their own course…to achieve freedom from the bonded servitude and usury under which most people will exist…and to experience a satisfying life.
They will learn how to produce their own food…and provide their own shelter. They’ll learn how to design and make things…and they’ll discover how to acquire the means of exchange through owning and operating their own enterprises.
That’s it for this week. Feel free to comment or ask questions. Until next week, keep growing – and take it easy.
Frequent heavy rain stopped work on this system, this week…but sand beds were still the subject of discussion elsewhere in the world.
Fresh on the heels of the iAVs/DWC comparison study conducted by Hisham El Essawy at the American University in Cairo (AUC), is another study that sought to compare lettuce yields between a DWC and with a “sand-bed system.” Like its predecessor, the latter study, by Lobna Salem (also from AUC), failed to optimise either of the units thus bringing the study outcomes into question.
While I’m delighted that universities are starting to demonstrate an interest in iAVs (even when they are not aware of it), I regret that we were not associated with the researchers because these comparative studies would have been better served if they’d sought advice about what sand can do…particularly using the iAVs method. The rainy weather provided an opportunity to take a close look at both theses.
The really interesting thing that has come out of the two AUC studies is the confirmation (yet again) of the versatility of iAVs. We’ve seen some outrageous deviations from the instructions and guidelines…and yet the iAVs (or other sand-bed aquaponics) still grows plants…and better than any other media bed that I’ve seen.
New Worm Farm
The new worm farm is now in operation. I put some coco coir into the bottom to allow the worms somewhere to retreat if conditions weren’t to their short term liking. I then transferred the worms – and several kilograms of castings. I topped the bed off with several layers of weathered cardboard smeared with the larvicast out of the BioPod. I’m planning to use worm castings in the evolving organic hydro units and while, we’ve got modest stocks of vermicast, we’re also experiencing cooler weather.
New Ebb and Flow system
The old worm farm is now the new ‘ebb and flow’ hydroponics system. The grow bed is a fraction under one square metre in area…holds about 200 litres when full, and is, at the moment, part-filled with clay pebbles. Below the grow bed is a 200-litre nutrient tank. A small submersible pump controlled by a timer…and some simple plastic fittings…facilitate the pumping of water from the nutrient tank up to the grow tank. An electro-mechanical timer – and a simple standpipe arrangement – ensure that a predetermined amount of water gets pumped up. Once the pump is shut off, the water drains back into the nutrient reservoir… and awaits the next irrigation event.
Organic Hydro Biofilter/Brewer
It’s been about a week since the ammonia level in this system dropped to zero. I’m currently waiting for nitrite levels to rise.
Seedlings on Steroids
I’ve left a bunch of pak choi seedlings in the seedling propagator – well past the time that they should have been planted out. I’m keen to see how they turn out so I’m going to put some of them into 2″ NFT pots – and some others directly into the clay pebbles in the new ebb and flow system.
The Emerging Vision
The overall plan for Havemore Farm is to turn it into a fully-functioning waste transformation micro-farm…showcasing a variety of food production (and other lifestyle development) options.
As recently as a few months ago, most of our food production capability had been mothballed.
We have considerable capacity once it’s all up and going.
But it’s all useless if it’s sitting idle. so, sometime back, I decided that, before taking on any new projects, I’d put everything that I had lying around to work growing food. I decluttered the backyard and unearthed a number of tanks and tubs…and incomplete projects.
That means that there will be new projects happening soon. They include:
- IBC Test Bed system
- Mega Bin duckweed unit
- Organic Hydro Biofilter/Brewer 2.0
- Pond Biofilter
More details on the new projects will be available next week.
Got any ideas or suggestions for improvement in this weekly report? I’d love to hear from you…and it doesn’t matter what it is…I’ll give it a try. More pictures…less reading? Bigger pictures? Prefer video? More links?
Until then, keep growing – and take it easy.
This week, saw work begin on the sand biofilter for the iAVS…and the DWC grow tank.
Since Havemore Farm is a constantly changing feast, my first task was to clear the site that I had allocated to the grow bed/tank. My NFT system – and a couple of shallow beds – were making temporary use of the space…so they needed to be moved.
The NFT was easy. I simply created a new base for it – using cement blocks – and moved it across to its new temporary location.
The shallow gravel beds required a lot more effort…including the removal of 600kg of gravel. Having seen almost as many incarnations as the Buddha, they are now stacked up – over behind the pond – awaiting their next deployment.
Given that the new bed/tank will weigh around 1.4 and 1.0 metric tonnes respectively…and my particular circumstances are such that they need to be above-ground, they are of robust construction. I used cement blocks for the supports…and treated pine sleepers and formply…for the grow beds.
I began to dig the holes for the sump tanks and it wasn’t long before Fate rolled up to the party…revealing some sewage plumbing right where I wanted to put the first sump tank…and forcing a change of direction for both me – and the sump tanks.
New Worm Farm
I already have a worm farm, but it’s in a repurposed ebb and flow grow bed – and I can make better use of it in that role.
I own three mega bins…750-litre HDPE produce bins. I’ve used them for all manner of things…often as fish or water storage tanks. Anyway, one of the bins has developed a leak, so its tank days are over…but it is adequate for use as a worm farm.
Organic Hydro Biofilter/Brewer
It’s been an interesting week following the startup of this little unit. Follow my meanderings…HERE.
Getting the Right Perspective
The first photo shows the RAS, the iAVs and DWC beds with the duckweed pond in the foreground. The second image shows the opposite view – from the pond back to the chicken house and soil pit.
The Bloody Chickens
Egg production has been a real issue in recent months. It’s been up and down like a honeymooner’s pants. I’ve tried all manner of things to fix it…but I’m often my own worst enemy when it comes to dealing with problems like this. Process improvement requires that you change only one variable at a time…otherwise you’ll struggle to know which variable brought about the improvement…but I’m sometimes too clever for that.
This week, I finally cracked the code. So, if you keep chickens and you want to know what the issue was, see HERE.
Organic Hydro Biofilter/Brewer
It’s been an interesting few days in my quest to understand more about organic hydroponics in general…and human urine in particular. Follow my daily progress…HERE.
I’ve set up the fish side of the proposed comparison.
This unit is my microFish Farm 2.0…a stand-alone recirculating aquaculture system. It comprises a 1,000-litre fish tank, two radial flow filters, a packed media filter and a moving bed biofilter. This will be attached to a 1,000 DWC grow tank.
This is the fish side for the iAVs…and it will be attached to a 1,000-litre sand biofilter/grow bed.
Since this project is a comparison of DWC with iAVs, it’s probably useful to make the point, at this stage, that DWC requires more equipment than iAVs…so capital expenditure will be higher. In this particular case, the cost is over double that of the iAVs.
My workshop often takes on the appearance of an exploded goat (shit everywhere)…but, this week, my minimalist self got in and de-cluttered it. The workshop space is only 6 metres by 4 metres – and it has to perform a variety of function…including building food production systems, making and mending and tool/equipment storage. Suffice to say, compromises are necessary.
Betting that it will stay as clean and tidy as it is now, won’t get you big odds at your online betting shop. C’est la vie!
Inspired by a study undertaken at the American University in Cairo, I’m preparing for my own iAVs/DWC comparison.
The obvious question that arises is..”If the AUC already did such a comparison, what’s the point of repeating it?” The answer is simple. While the AUC study found that iAVs was the better method for Egypt, the methodology was flawed to the point where neither system was able to perform as it should.
The project requires that I build two systems – side-by-side – so that they are, as near as practically possible, operating in the same environmental conditions.
The fish tanks have a capacity of 1,000 litres. The DWC grow tank also has a capacity of 1,000 litres. The sand biofilter will contain around one cubic metre of sand…equal to a 1,000 litres in volume terms. Each of the filtration modules is 200 litres.
With the iAVs, all of the fish wastes will go to the sand biofilter. In the DWC, all fish wastes will flow through the filtration modules with a view to capturing them, processing them (out of the water flowpath) and returning them to the system – less the sludge.
I’m currently gathering the hardware to build these systems and I hope to commence their construction in the coming week.
A few weeks ago, I built a little biofilter/brewer to enable me to learn more about cost-effectively turning organic substances into plant-available nutrients.
The biofilter consists of a 20-litre plastic drum into which I’ve placed a 750-litre/hr pond pump.
The 20-litre bucket is fitted with a lid into which I’ve drilled some small holes. A 10-litre bucket sits on top of the 20-litre drum – supported by the lid with the holes. I’ve placed a coir garden pot liner inside of the 10-litre…and part-filled it with coarse sand.
The sand will filter out any solid materials and will serve as bio-media…housing the nitrifying bacteria and other microbes that will convert the organic substances that I want to decompose so that they become plant-available.
The simple plumbing arrangement allows me to adjust the rate of flow through the top bucket while also stirring – and aerating – the contents of the 20-litre bucket.
I’ve just started it up and my first trial will involve one of the most accessible organic substances of all – human urine.
Notwithstanding, it’s alleged ‘yuk’ factor, urine is very interesting stuff. It contains valuable nutrients which are wasted by flushing it down the toilet. But its role in the waste cycle doesn’t end there. We waste millions of megalitres of potable water – using billions of dollars of infrastructure – flushing it into waterways where it (along with the other substances in wastewater) harms the aquatic and marine environments.
Stick with me – and we’ll both learn more about making – and using – ‘pee tea’ from urine.
My love affair with my new BlueLab Truncheon continues unabated. I always knew that hydroponics, at the backyard level, was able to produce clean fresh food…quickly! I never realised, however, that it could be made so easy. Ensuring that my hydroponics plants are receiving the nutrients that they need, is as simple as filling up the water reservoir – and adding nutrients. The Truncheon then indicates when the nutrients at the correct level.
I’m busy putting all of the hardware together for a deep water culture (DWC) unit…and my first iAVs system. I’m planning to undertake a comparison of the two systems. The grow tank for the DWC…and the sand biofilter/growbed for the iAVs…will be made of treated pine sleepers and will be lined with low-density polyethylene liners. I had planned to put the fish tanks in-ground but I have a complete 1000-litre recirculating system…and a spare 1000-litre tank…that I have lying around. Not only will it save money but it will save time, too.
In case you were wondering, the little box arrangement above the moving bed biofilter (in the photo above) is a native bee hive – a very expensive way to provide a living space for native stingless bees.
This week, we’re planting out kale seedlings…and harvesting some lovely pak choi.
Take it easy…and I’ll see you next week.
My hydroponics systems are producing at a satisfying level but, it’s time to ramp things up a bit, so I’ve invested in a Bluelab Truncheon…and a pH tester.
The Truncheon measures nutrient strength…and the pH tester (not surprisingly) measures the pH of the nutrient solution…and it’s the pH that determines nutrient availability to the plants.
The Truncheon got its first workout earlier this week. It showed that the nutrient level in the seedling propagator was inside the recommended range but that the level for the NFT and gravel systems were on the lower limit. Based on this information, I added more nutrient to the reservoir. I love this device already.
Food production got off to a slow start this year but I resolved to make it the main priority – and we’re at full throttle currently. We’ve got 72 NFT holes filled with pak choi, silverbeet and a few strawberry runners. Another 4m2 of hydroponic grow beds is full of kangkong and silverbeet – and another 30m2 of wicking beds are growing pak choi, silverbeet, Russian comfrey, pinto peanut and a mix of edible herbs.
I receive frequent questions about iAVs’ performance around things like annual fish production, plant spacings, water use efficiency and the relationship between fish feed and plant production. While I can recall most of the key numbers, I’m always a bit hesitant to quote them off the top of my head – so I’m inclined to want to check them for accuracy before committing myself. The problem with this is that the metrics are spread throughout several documents – and finding them can burn up some time.
To make the task easier, I’ve put them all together in a single document. There are others that are still awaiting discovery among Mark’s responses to various blog comments and they’ll be added as they come to hand.
One of the things, about which I’ve wondered, is why people are so attracted to aquaponics. I don’t mean the often quoted benefits – like reduced water use, faster plant growth and the non-use of chemical herbicides and pesticides. They’re frequently cited by newcomers to the discipline, but they’re generally a rationale rather than the key attraction. Anyway, I wrote a very brief article on what I think attracts people to aquaponics.
I’ve just discovered ‘food swap meets’…local gatherings where people who grow food swap their surplus with other growers for food items that they don’t have. Great idea!
I’ve been pondering the question of why people engage in aquaponics and, notwithstanding all of the tangible benefits of the method, I believe that, for most people, it comes down to three things.
1. The bragging rights associated with being able to grow fish. If you can grow fish, you can do something that a lot of people can’t do…and that allows you to stand out from the crowd. And that, it seems, is very important to many people.
2. Most people are not good gardeners but, aquaponics allows people who are not good gardeners to grow plants – even if to a limited extent. The major critical success factor associated with gardening is the timely delivery of water and nutrients to the plants – and aquaponics (and hydroponics) provide this.
Note that I didn’t say anything about doing either thing – fish or plants – well. Most of the people who believe that the basic flood and drain system is OK, fall squarely into this framework. And that brings me to the third reason.
3. The mistaken belief that aquaponics is easy.
Aquaponics is only easy if you subscribe to the false belief that basic flood and drain systems are adequate places to raise fish.
If you want to grow plants quickly and easily – and with relatively few hiccups – go for hydroponics. A nice little well-designed hydro system is the closest you’ll get to a perpetual motion plant production machine.
Hydroponics is far easier to build, much cheaper, far more predictable, easier to operate and, with a little knowledge, far more productive than the average backyard aquaponics system.
Information specific to the performance of iAVs is scattered throughout the documents on this site. As such, getting a clear picture of what iAVs can do, can be a protracted process.
I’ve assembled this list of performance metrics to assist the process. This list is not exhaustive and will be expanded as I get teh opportunity to read through Mark’s comments on various posts.
- Yields attained in Raleigh, NC indicated that this automobile-sized space could produce 150 kg of fish and 1,100 kg of vegetables per year which assumes a periodic harvest as both the fish and vegetables reach an appropriate size…an average of 3 kg (7 lb) fish and 21 kg (46 lb) vegetables each week). 1
- 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. 1
- Each 1.0 kg of fish weight gain provided sufficient quantities of all required plant nutrients to sustain 2 tomato plants yielding 5-7 kg of fruit per plant over 3 months.
- Tomato yields exceeded 6.8 kg (15 lb) per plant.
- The rate of water input (replacement of evapotranspiration losses) in the IAVS technique ranges from 1 to 3% of system capacity per day.
- The IAVS technique requires only 11 cubic meters of water per year for each 1.0 cubic meter of system capacity (at a 3% per day rate of loss).
- Depending upon the crop, season, and the biofilter to tank volume ratio, this technique permits from 120 to over 300 crop applications with each unit volume of water.
- Each litre of water employed can produce, in fish and fruit, 0.7 grams of protein,7 kilo-calories food-energy, and most essential vitamins.
- The water efficiency of iAVs is at least 13 times that of UVI raft (DWC) aquaponics – and that doesn’t even account for their failure to factor rainwater into their water use data.
- Including annualized losses for evapotranspiration and incorporation into biomass (food) at 85% of total input and a seepage loss of 6%, each litre of water utilized by the IAVS technique can produce 6 g FW of fish and 17 g DW of vegetables.
- Collectively, tilapia and tomato yields result in 0.7 g DW of protein and 7 Cal. (or 7,000 calories) per litre of water used.
- As the size of the biofilter per fish tank volume is increased, the yield of tomato (for example) decreases from 27 to 19 kg per square meter per crop, but the fish grow 20% faster. This results from a reduction in nutrient availability per plant but an increased filtration capacity (cleaner water) for return to the fish with increasing biofilter size (increasing plant number).
- The sum of the water pumping intervals in the technique developed at NCSU is less than 2 hours per day. The energy demand of this technique is approximately one-twelfth the energy requirement of other recirculating aquaculture techniques.
Fish and Fish Feed
- Each kilogram of feed input to the system will result in the production of approximately 0.75 kg of fish and 6.70 kg of fresh vegetables.
- Fish yields ranged from 50 to 70 kg per cubic meter of water per year (0.41 to 0.57 lb/gal/yr).
- Feed conversion ratios for fish of average market size (0.25 kg) ranged from 1:1.1 to 1: 1.3.
- Some numbers…for example, those relating to the ‘Carpark Model’…may seem at odds with each other. The lower figures relate to low-tech applications…like those typically found in remote villages…where the higher figures apply to medium-tech situations.
- iAVs has never been optimised. The research trials sought to achieve two goals…to prove the concept (the Proto ’86 trial)…and to establish the relationship between the fish tank and sand biofilter volumes (the Ratio 411 Trials). These metrics are simply the outcome of those trials…and provide a performance baseline. The production outcomes were exceeded by Boone Mora and Tim Garrett in the USDA-funded Commercial iAVs Trial…and, it’s reasonable to expect that they will be exceeded by other operators as more is learned about the method.
We’re getting rain on a daily basis and our water tanks (10,000 litres capacity) are full. I have another 6,000 litres of temporary storage deployed, too. In addition to storing water, these ponds, tanks and tubs are also used to grow duckweed.
The hydroponics systems – NFT and gravel media beds – are going well. I’m growing kangkong in the gravel beds – for the chickens and it’s a winner. It grows quickly and it’s a quality greenfeed…and great for stir-fried dishes, too.
Most of the wicking beds are planted out to vegetables like pak choi and silverbeet (Swiss chard). At the moment, my focus is on fast-growing plants for food and fodder.
Our little ebb and flow seed propagator continues to exceed my expectations. I’m currently using it to grow kale seedlings.
The chickens have settled down and are finally laying enough eggs to meet our needs…still with scope for improvement. I’m now able to feed BSF larvae and homegrown green feed (in addition to their organic base ration and kitchen scraps) on a daily basis. Although I provide the organic ration on an ad lib basis, my goal is to reduce their consumption of it (it’s expensive) by supplementing with homegrown ingredients.
The big win, this week, was the arrival of a bulk-a-bag of sand (made from recycled glass). A gift from an old friend, the glass sand will be used to build my first iAVs system.
Aspiring iAVs operators are often confused about how to approach their first build.
We always recommend that newcomers to the method start with something small…a fish tank of 500 to 1000 litres and a sand biofilter/grow bed of 1000 – 2000-litres…which is 3m – 6m by 1metre wide by about 400mm deep. This is your learning prototype.
As you get your head around working with iAVs, you can expend the number of such units to four. This allows you to do side-by-side comparisons of fish species, plant cultivars and operating parameters…a very useful thing indeed.
If you continue to extend your system, this way, you will end up with 16 such units…and your own research facility…and you will quickly establish yourself as the iAVs expert in your area. At that point, you will be harvesting fish on a weekly basis. Not only will you be drawing income on a weekly basis but you will also be able to expand your operation to become an iAVs demonstration centre…where you can even entertain fee-paying students.
Before we reach that point, however, we need to know what your iAVs goals look like. Are you just looking to grow food for your family? Or do you want to sell food into your local market? Or do you want to do that…and run a training business, too?
Regardless of your aspirations, I recommend the modular approach because it allows you to grow commensurate with your knowledge and skills. It also allows you build your operation over time using the production income from each unit to fund those that follow. This self-funding idea applies from your very first iAVs…since you’ll both be taking home clean fresh food to your families…food that you’d have to otherwise lay out money for.