We often seen the word sustainability used in conjunction with aquaponics but just how sustainable is it?
Water use efficiency and the absence of herbicides and pesticides are powerful arguments in support of sustainability…..and so is the conversion of fish wastes into plant food.
But these are only part of the picture.
Any notion of sustainability has to acknowledge the following:
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The use of wild catch fishmeal in the manufacture of fish rations.
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The cost of the energy required to run the pumps and environmental control systems.
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The amount of energy embodied in the components used to build any aquaponics system
Most aquaponics systems rely on pelleted rations largely made from fishmeal. It can hardly be claimed that aquaponics is sustainable as long as it depends on rapidly declining fish stocks for its core ration ingredient.
While there has beeen some work done on alternative feedstuff for freshwater fish, there’s much more to be done before aquaculture (and aquaponics) can cut the fishmeal umbilical.
The operators of most small aquaponics systems would struggle to quantify their energy costs. If the cost of the energy that it takes to grow fish and plants exceeds the value of the fish and plants, then it could hardly be described as sustainable…….financially or environmentally.
Currently, many aquaponics systems are made from plastic or fibreglass components. These components are relatively expensive which raises the question of return on investment. How much clean fresh food does one need to produce to cover the cost of the production system? How long does it take to recover the cost of your investment?
The other issue is that the plastics and fibreglass industries are largely reliant on the oil industry for their feedstocks. How can something be sustainable as long as it depends so heavily on declining oil stocks?
OK……so while aquaponics is more efficient in its use of water compared to soil-based gardening systems, it certainly doesn’t stack up so well in other areas of sustainability.
So, what’s the answer?
Aquaponics (like all intensive farming systems) is largely dependent upon the energy provided by fossil fuel so designing systems to minimise energy use is a logical place to start.
Minimising how far and how high you pump water is one way of reducing energy costs. Selecting system components for their energy efficiency is another way.
Most aquaculture species require supplementary heat for year round production. The use of passive solar heating and insulation to reduce heat loss are central to reduced energy consumption.
While plastics and fibreglass lend themselves very well to aquaponics, perhaps their application should be limited to those system components which demand their use. The biggest user of plastics and fibreglass is growing systems.
Using a broader range of growing systems – including some which are soil-based – is one way of reducing the use of composites. Building growing structures out of plantation timber (lined with plastic) is another way.
Finding alternative feedstuffs for fish is essential if aquaponics is going to have a long term future. The answer to this problem is the inclusion of more organisms into the integration.
Don’t get me wrong. I think aquaponics is great.
Its water use efficiency and the symbiotic relationship between fish and plants entitles it to kudos from the outset.
Its current dependence on fossil fuel energy and fish-based diets, however, makes aquaponics (in a sustainability context) a work in progress.
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{ 27 comments… read them below or add one }
Yes to me a truely sustainable aquaponics system is the holy grail of sustainable living. I think the Chinese may have discovered it about 1000 years ago. Chinese subsistence aquaculturalists for centuries have employed certain species of carp to occupy various niches within the same pond. High stocking densities could be grown as each species would take up a particular position within the water column. Energy input was almost exclusively solar. Omnivores would consume the algae and detritivors would consume their waste. Crops of vegetables were simply grown along the edges of the ponds and periodically splashed with water by the farmers.
So simple yet so complex. No tanks, pumps, fittings etc but a delicate ecological balance no less. And unfortunately something we cant replicate in Australia, not with carp anyway. But perhaps with some of our more hardy natives like eels, catfish, and mussels…hhmmmmm.
Old Trout……..the Chinese certainly understood the value of integration. Over time, we will develop similar local integrations to those used by the ancient Chinese. Integrated aquaculture is still in its infancy in places like Australia.
I’m part of a sustainable living, suburban cohousing community. Aquaponisc is in our sights (garden snails too!) I appreciated your no nonsense approach about sustainability, that is, how it really is. This is very important information.
Thanks Robyn
Pinakarri Community
Fremantle, Western Australia
Robyn Williams…….thanks for your kind words. I hope you continue to enjoy the posts…….and to find them useful.
I’m exploring aquaponics, hoping to set up a system in the coming months. Thanks for the great info. Have a question — my impression is that duckweed and other water plants, as well as earthworms can supply all the food needed by the fish in a system. Is this not the case?
Carolyn Allen……while all of those can supplement a pellet diet (and which and how much of each depends on the fish species being raised), reasonable growth rates depend on a balanced diet. Pelletised commercial rations are formulated to meet the specific needs of the aquatic organism for which the diet is designed.
In an aquaponics system, what (and how much) you get in the way of plants is heavily influenced by what you feed the fish.
With respect I like what you are saying but you need to do your homework on the fishmeal content of the feed.
Andrew……feel free to share your knowledge and experience with us.
excellent remarks, Gary
we should not kid ourselves: we are a long way from the completely closed loop system that nature is and will never get there
but lots of improvements are possible
like diminishing grow bed depth (misconception 3) in favor of materias used, weight and surface
optimising pump performance is a big one (today’s pumps perform very poorly, on average less than 5%).
taking advantage of this optimised pump performance for aeration purposes (aerators and blowers perform even worse than pumps).
absorbing and applying all possible solar energy, be it for heating, cooling or electricity
passive solar greenhouses, well oriented, in soil stocking of solar energy, it’s all there
we need to apply it all
frank
Frank.…….optimising pump performance is something that I definitely need to learn more about.
Like most people who operate smaller aquaponics systems, I find myself being seduced by the sheer convenience of submersible pond pumps which are probably the least efficient of the options.
I’ve been thinking of using small centrifugal (non-submersible) pumps on my next system.
I’d appreciate your thoughts on the whole matter of pumps generally.
if you only look at the extremely poor design of small pump impellers and housings and compare these to their (bigger) industrial brothers and sisters it is easy to understand why they do not perform: they are a shame, especially if you know that once a good design is established, the extra production costs at the levels pumps are manufactured means just a few cents, be it dollar- or eurocents per item. But the whole concept of centrifugal pumps for our purpose is to my opinion a wrong one as they are suited for 10, 20, 30 meters head and we only need 1 to 2 meters.
I have a strong belief in propeller pumps (which are positive displacement pumps, made for high flow and low head) like in the propellers that move forward a boat. I should take more time to experiment with model boat propellers.
Gary, how do I go about keeping informed of replies on your blog? is there an automatic system that will warn me i.e. by e-mail?
frank
Frank…….one of our Australian members (now living and working in the US) went down a similar track with pumps. He advocated a ship’s propeller sort of arrangement in a housing (lifting the water just centimetres rather than metres) as being much more efficient.
I’m no expert when it comes to how you track blog posts……but I’ll make some enquiries for you.
Isn’t the use of BSF larvae (via Biopod) as well as duckweed considered a sustainable food source for a multitude of fish species?
As far as sustainability is concerned, my greatest disappointment was when I learned about the necessity of iron chelates and other mineral supplements that are deficient in the system.
Since I’m very much into Humanure composting, it seems a huge step backward to have to revert to a simplistic “NPK” mentality. Ideally, there should be myriad elements for plants to absorb (which is achieved very easily through simple composting), though the dilema here is that using a dirt media for aquaponics won’t work(?)
I can imagine toxic amounts of minerals leaching into the fish tank, clouding it considerably. If, however, duckweed was grown in the tank to absorb the excess nutrients, could there possibly be an integration between the use of humus in the grow bed and fish being able to survive in a rigorously inocculated duckweed tank?
Or perhaps one could just mix water with their compost, and use the leached liquid compost as a supplementary way of adding minerals to the system, doled out in small amounts. Any thoughts?
Additional thoughts: Is it feasible to set up a few solar panels/wind turbines to power a decent water pump, or is the energy useage too intense for them to handle (assuming there are no winter months that greatly reduce solar potential)?
Mike……..BSF larvae and duckweed are certainly a sustainable ration ingredient for some species.
The good news about your convcerns about the need to add iron chelate, potassium and calcium is that, if you run your system pH at the lower end of the scale (say pH 6.0 – 6.3), it is not necessary to add those elements.
Duckweed is capable of bio-remediation but whether it would take up enough of the nutrients in a recirculating aquaponics system would require some controlled testing.
Fish wastes from an aquaponics system can be isolated and aerobically digested…….and the nutrient-rich liquor can then be decanted from the watery sludge. The liquor can be added back into the system and the sludge given to the worms or compost heap. Not only is this possible but, in my view, it’s desirable.
I imagine that worm tea could be added to an aquaponics system to provide another source of organic nutrients.
Mike…….it’s certainly possible to run an aquaponics system on power provided by the sun and wind. The problem is that, as things currently stand, the cost of generating power with sun or wind usually exceeds the cost of the aquaponics system so most people don’t bother……particularly since 24 hour operation would require a battery bank to ensure a continuous consistent supply of energy.
We usually find that the people most likely use solar power to run backyard aquaculture systems are those who don’t have any choice…….and who are inclined to apply a different financial approach to everything they do that requires energy.
I’m aware of several small systems that are solar-powered but most people will baulk as the cost.
Gary,
Thank you for very informative reply. I’ve been reading some of your other posts and find them to be very helpful.
I’ve gathered that the nitrates contribute to the mild acidity of the system, thus it is paramount to prevent anaerobic conditions through the periodic removal of solid wastes. I wonder, is it considered standard protocol to have a gravel bottom for the fish tank where beneficial bacteria can grow, or do most people just leave it as a plastic bottom?
I’ve also read that raw egg yolks added to the fish tank can act as a natural clarifier, though I’m not sure if that can be considered a primary solution to the buildup of solid materials on the bottom.
In case you haven’t already mentioned this, do you aerobically digest fish waste by physically placing it into a container of some sort and pumping oxygen into it?
Mike………I’m pleased that you find the material useful.
It’s important to remove solid wastes (particularly in a small system) because of their effect on oxygen levels as much as anything.
Most fish that die in an aquaponics system, do so because oxygen levels in the water fall below the level needed to sustain the fish.
This may be the result of equipment failure or interruption to the power supply or (just as fequently) it may be a convergence of events including high levels of suspended solids, uneaten food in the tank, hot weather or an algal bloom.
I wouldn’t recommend having gravel on the bottom of the fish tank because it would be likely to trap solids and create the sort of anaerobic conditions that should be avoided in an aquaponics system……and it would be very hard to clean out.
I haven’t heard of using egg yolks to clear water. I’d be concerned that in using eggs to resolve one solids issue you’d be creating another one. I use mechanical and biological filtration devices.
When it comes to aerobic digestion…….yes you can do it and yes I have. It is only a matter of using air to stir the watery solids until they mineralise and release the nutrients that are bound up in them. The duration of the stirring depends on the volume of watery solids and the concentration of the solids in the liquid.
Gary,
Considering that aquaponics is still very reliant upon fish meal, (since duckweed and BSF can only go so far), shouldn’t there be some concern over the bio-accumulation of PCB’s and mercury in the fish aquaponicists are raising for consumption?
I’ve pondered the idea of raising small fish to become food for, say, catfish or tilapia, however, the dilema continues with feeding the small fish that feed the larger fish. One hope is that as one moves down the trophic pyramid, one will eventually arrive at autotrophs (could there be fish that are strictly herbivores?). Would constructing such an ecosystem be feasible for microponics or are the oceans, lakes and rivers the best candidates? My mind naturally assumes that the food web of land animals would be similar to that of aquatic species, (wolves eat deer; deer eat plants…and the occasional insect perched on a leaf).
As you have said, finding a sustainable food source other than wild fish meal is crucial to the longterm viability of aquaponics.
Mike…….there are lots of omnivorous fish species that eat a mix of algae, plants and fish. Tilapia is one of the most widely cultured fish species in the world and it can live on algae……but it grows much faster on a higher protein diet.
Many fish species would probably live on a lower protein diet but, once you get outside of the optimum growing season, energy costs rise (for either heating or cooling) and the fish’ appetites decline and production costs rise.
Raising fish commercially means growing them as quickly as possible (usually within a seasonal constraint) so that means shovelling a high protein ration into them.
In recent weeks, I’ve discovered that there is a great deal of work being undertaken to develop alternative diets for aquaculture.
One of the more promising ideas is the use of krill (tiny shrimp-like organisms) which – at this stage – are very plentiful. Australia’s national research organisation CSIRO has also made some recent announcements about the successful use of canola and flaxseed oil in fish diets.
There are plenty of opportunities for experimentation on the backyard front. While I’ve mentioned Black Soldier fly larvae and duckweed, worms, feeder roaches, silkworms and other fly larvae all offer some hope for the micro-farmer who want to produce their own home-grown fish rations.
Since home-made rations will usually amount to longer grow out times, their use will have to be reconciled with environmental control strategies (like greenhouses) so that the growing season can be extended.
Gary,
I think I’m starting to understand what you’re getting at with the idea of krill. I was reading that they’re so important because they’re the second-to-last organism on the food chain (phytoplankton on bottom). Since krill feed on phytoplankton, it seems probable to grow phytoplankton to feed to the krill, while the fish feed on the krill. Perhaps one could have a separate tank comprised exclusively of krill
If you haven’t already found this website, check out this site for harvesting phytoplankton: http://www.melevsreef.com/phytoplankton.html
Mike……the krill that I was talking about is the stuff that is caught in the wild.
Of course, while that might be a useful source initially, man (being the resourceful creature that he is) will eventually harvest that natural resource to the point where the whale don’t have enough to eat.
There’s been relatively little practical research been done on breeding organisms for freshwater aquaculture but I feel that there’s real scope for such work.
Thank you all for your valuable comments. Its great to read some balanced reflections.
I remember hearing Bill Mollison in a Permaculture design course describe the roll of ducks in aquaculture systems (like rice paddys) as a way of providing fish food through their manure.
An example – http://www.fao.org/docrep/004/ac155E/AC155E15.htm
Which looks like a variation of what Old Trout was referring to in the first response.
Does any one have any thoughts on this prospect for aquaponics?
Martyn……ducks are better suited to a pond-based aquaculture system …….or a tank-based system that does not recirculate. The duck poop would make a shocking mess of a fish tank.
If you want to grow Tilapia in Australia (except in WA) be very careful as it is illegal to grow.
How do you feel about trapping wild insects as part of a feeding regimen?
Sample traps: http://www.inhs.uiuc.edu/cwe/wwwtest/collect/HTML/d18.html
Andy…….I like the idea of using insects as windfall food for home-grown fish.
Thanks for posting the link on insect traps.
Depending on the location, a low wattage light bulb suspended over the fish tank will attract flying insects which beat themselves senseless on the bulb and fall into the tank……..to the delight of the fish. The only issue is that, in certain circumstances, this method can produce too much food with the result that much of it lies uneaten on the bottom of the tank.