Aquaponics is great.
And the flood and drain model is particularly interesting…..and useful.
But what if you wanted all of the benefits of aquaponics but none of the complexities of rearing fish?
Or what if you can only grow fish during a particular season? What do you do to keep your plants going during the off-season?
Well, there is a way….Vermiponics.
I first learned about vermiponics (a couple of years ago I think) through a post on a mailserve list by an American named Jim Joyner. He described his approach during a subsequent exchange of emails.
OK…..so how does it work?
Picture a basic flood and drain aquaponic system comprising a fish tank, a pump and a gravel grow bed or two.
At the risk of stating the obvious, you’d normally have fish in the fish tank…..but with vermiponics you substitute another ammonia source in place of the fish.
Most aquaponicists are aware that worms populate mature flood and drain systems and that they help to mineralise the solids in the grow beds.
In vermiponics, worms serve the same function except that their food source is something other than fish poop (like finely chopped vegetable scraps or rabbit manure)…..and rather than putting the food into the water, it is placed into the beds.
So, why would anyone want to do this?
The tilapia that Jim used to stock his aquaponics system, were only viable during the warmer months. His problem was that he needed something to power his AP system during the cold months.
Where most aquaponicists would simply look around for a cold water fish species, Jim (whose principal interest is in growing vegetables anyway) decided to trial an alternative ammonia source and rely on the nitrifying capability of the flood and drain process and the worms in his system to produce the nutrients for his plants.
He experimented with rabbit food before he realised that worms feed on microscopic life forms (rather than the food on which they grow) so he tried fermenting the rabbit food. Eventually, he arrived at the fact that the most efficient way to ferment the food was to put it through the rabbit first, so he started using rabbit manure.
OK…..so what are the advantages of vermiponics over aquaponics?
- The risk of catastrophic failure is much less.
- While worms need oxygen they can access it more effectively than fish.
- Worms will survive a power or equipment failure much longer than fish will.
- It’s much less expensive (in terms of energy costs) to run a vermiponics system than an aquaponics one.
- It’s much cheaper to feed worms than it is to feed fish if vegetable production is your desired outcome.
- Worms will also thrive on a much wider range of feedstuffs; many of which are so-called low value wastes.
- Worms will thrive in a much broader environmental range than fish will.
To summarise, when it comes to growing plants, vermiponics is cheaper, more efficient and is more risk-averse than aquaponics.
Some other thoughts:
Jim buries the food for the worms in a trench in the gravel grow bed.
Glenn Martinez (who lives in Hawaii) has a slightly different approach, He inserts a gravel barrier (90mm PVC pipe with plenty of 10mm holes drilled in it) into the grow bed and places the food source inside. He places a cap over the top to prevent vermin or sunlight from accessing the food scraps (worms are photo-sensitive).
Either flood and drain or surface-based continuous flow watering can be used. Timer-controlled flood and drain would be more energy-efficient particularly since the pump could be switched off overnight without endangering the system.
If you were to opt for continuous flow, you could get away with a much smaller (and much less expensive) container than a fish tank.
Either way, the water is going to be well-oxygenated…….which is good for the worms, the plants and the bacteria that drive the nitrification process.
It would be possible, through experimentation, to arrive at optimum worm feeding rates (and feed ingredients) for the plants being grown.
While vermiponics may not be the most effective way to grow worms for sale it could still be done. Placing a container of suitable food on the surface of the grow bed (while withholding it at their usual feeding spots) will attract the worms to the container which can then be removed to a bench where the worms can be sorted from their bedding.
The other possibility (and the one which led Jim to the whole thing anyway) is that a vermiponics approach may just be a useful way to keep plants going during the fish off-season…….whether that be in hot weather for those who grow rainbow trout or in colder weather for those who grow tilapia or jade perch.
Vermiponics is also a subject dear to Dr Brett Roe, a researcher at the Central Queensland University. He has been experimenting with various integrations of fish, crustaceans, plants and worms (in something he’s titled Vaquaponics) for several years. I had the good fortune to learn from (and share a platform with) Brett at the 2009 Commercial Aquaponics Course held in Brisbane.
Anyway, regardless of how it’s used (or where it first came from), it’s a very interesting idea and one worthy of further investigation. While it won’t replace aquaponics at Creek Street Micro Farm, it might become another means by which we grow clean fresh food.