Backyard Aquaponics
A place to discuss aquaponics

yeah, I think the low-energy has potential. We are making progress. Jimbo has showed that it is possible to run a 800L system with 5 watts, and with a bit of tweaking, he might get even better flow.

Away from home for the weekend, so I can't tinker with the experiment. All I can do is sit and think. I priced a pallet of charcoal which by the eyeball test looks like about how much I need to fill the 2 half-ibc growbeds. $420+tax! And that was with a bulk discount. I don't want to go the cheaper gravel route because of the weight. It's likely this system will get moved around later, so I want to keep it light.
I could cut up cpvc or pvc pipe into short pieces but I haven't done calculations as to what that would cost and I doubt I would like the answer.
I was thinking of breaking up old bricks and maybe tumbling them to rub off the sharp edges.
Then I remembered that I researched making bricks one time because my soil has a lot of clay in it. Next logical step? Make my own clay balls-like hydroton. Hmmmmmm...
I have an aunt who is a potter, so I made the call with some questions. Its not something I can do in the oven and most potters are really protective of their kilns. She's willing to test fire a small bunch of them if the clay looks good to her. After doing some more googling, it seems that the higher temperature firing of the clay is to turn it into a non-porous container for holding liquids. Firing up to @ 1000 degrees (farenheit) is enough to harden the clay but leave it porous, which of course makes happy little bacteria condos. Apparently this can be achieved by firing the clay with wood in a pit or in some type of metal container with sawdust. That I can achieve. So, I may have to do some firing experiments after doing some clay digging and screening and drying and shaping and further drying...this could take awhile. But, free is always better...if it works and nobody gets hurt.

yay! I love it when I get to post a link to my home made goat dung scoria recipe.

if you put your clay into a cement mixer, and add water a bit at a time, it will ball up into very uniform balls. They wont be expanded clay, but they will be clay, and they will be balls. You can easily set the average size by adding water of more dry clay.

To create a porous structure, just add some sawdust or anything organic that will burn out in the kiln. The chemical change in clay is at around 650c or so, but although the clay will never be clay again, it wont be very strong and will break down, so yes 1000c is probably good for a terracotta.

the easyest way to fire it is in a big fire. Make sure it's very dry. 2 weeks in the sun and it wont explode if the is a lot of organic material in the clay body, and the ball size is normal hydroton size. Otherwise you might need to increase the temperature slowly.

If you fill a pit with sawdust and pour diesel over it, bury a bit of iron pipe and blow air into it you will easily get the temperatures required. use a compressor, a vacuum cleaner, or even a decent fish tank air pump would do it. the more air the hotter you go. We normally fire terracotta over around 12 hours. 10 of those are getting gradually to temperature, and the other two are to do with glazes.

But if you heat it hot enough for iron to glow cherry red, and keep it that hot for around 40 minutes, you should be right.

Try 10 litres of it in a little pit.

A decent fire of wood will also get to the required temperature. a match burns hot enough to force the chemical change in clay.

to get the organic stuff into the clay, you could put it all the way through by making the mix a bit wet, then adding a bit more dry clay.

or you could just ball up the clay, then add a wet mix of clay and sawdust to coat the balls. But more sawdust = lighter media.

very interesting BW...

I might try making some up by hand and wood firing them. We do bonfires once in a while just for social reasons. Broken pallets and such.
Also, I pondered cutting up foam like the type in furniture cushions into little chunks and then maybe scrunching up the middles with a zip-tie to make them into irregular shapes and leave some bigger voids. Very porous stuff, lightweight, but when saturated it shouldn't blow away. Would it support roots and plants? hmmmm....
I'm starting to like the idea of making a little wood fired kiln in the yard. I've read you can put the formed but still wet clay in an oven at about 190 F to remove the water without it flashing to steam and exploding. This speeds up the drying out process, and maybe will encourage some expansion, but not that important if it doesn't. Will save time.

if you are going to be firing your own clay, then make your own charcoal. It is very easy. Dig a pit, through in a bunch of wood, light it on fire, and bury the burning wood, with a few small smoke exhausts. Then, you could get more complex and build a retort.

I imagine charcoal and river stone mixed would work well.

yeah it shouldnt matter if a few few explode. it's not like youre making dinner plates or anything.

The expanding thing that some clay bodies do is often a fault in the body for potters. It can be caused by a few things, but I dont think steam could do it. At least not for you. The bloating (search for bloating in clay bodies - or something along those lines) is caused by the burning out of compounds not burnt out earlyer in the firing ie typically not things like sawdust, but perhaps some carbon depending on the atmosphere of the kiln. I think you get the best/worst bloating in a reduction atmosphere, where you limit the oxygen to the kiln. Potters do this to turn the oxides in glazes back to the metals or whatever they were before becoming oxides. The firing looks for O2 in the chemically bonded oxygen and eats it.

I think

Anyway the bloating of clay balls will most likely be caused by some oxide in the clay body gassing after the clay body has softened at heat, and also after it has sealed to some extent, ie formed a glassy skin on the outside, but also throughout the clay body. Doable if you really care and want to set up a new business, but not really a practical backyard, one off, goal unless you want to do it just because you can.

If I had to guess I'd say 10-15 firings to create a clay body that would do it. Potters normally add clay body, and glaze tests to normal, daily or whatever firings, so 15 test firings is no big deal. Just a matter of a few weeks. But it might not be practical to have that many bonfires:)

An easier way would be to just fill the clay body with things that burn out. wheat, sawdust, toenail clippings, whatever.

Try 10 different hand made balls, each numbered, with increasing, known percentages of sawdust, then fire them in a bonfire,

If you want to dry the before firing, something like a 44 gallon drum with a small fire under it would work. When potters fire their kilns they often fire overnight at around 80-160c to dry everything. Even then something large can still have some water, and have the side blow off.

The looser (full of organic material) your clay body is the less this will be an issue.

The reduced oxygen levels you use in charcoal production might add a bit of bloat to the balls, but I dont know if a charcoal fire would be hot enough to fire even a low temperature clay like terracotta.

Speaking of which, is the clay in question terracotta? All my info has been for a red clay with high iron content, but if it's white, it might require a hotter firing.

oh, i wasn't talking about making charcoal AND clay balls. But charcoal is easier to make than fired clay.

oops

It's not as if I actually pay attention or anything

but, if I remember right, pyrolysis of wood happens at around 450C. Would that be enough for clay?

no..

minimum is 650c for something that will no longer break down into clay, but will still break. 900c or so for a terracotta clay with lots of iron to make something that wont fall apart.

That's probably the problem with the counterfeit hydroton, low firing temperatures.

Hydroton is probably rapid fired to 1200c or something to make it bloat (dont quote me I made that number up) and at those temperatures it would start to get sticky as the iron oxide started to run (the black spots in hydroton are probably iron (or coule be a few other metals) so the balls would be kept on the move by shaking them or something. I think they use rotating kilns for hydroton.

I think that I only need 1000F to make primitive earthenware. A hard clay that doesn't hold water because it is porous, not vitreous which occurs at hotter firings, but does not revert to a liquid when wet. But that is a thought for another time. This posting is about results.
We got home from our travels sooner than expected and I got some test time in.
First, I bumped the pipe and tee up to 1 1/2" with the same 4" bell. Flow slowed down significantly to about 150 gph. So with the same size pipes I removed the airstones and inserted the airlines into the bell.

Woohoo! Now, this bugger was filling buckets with a gusto. Approx 300gph!
So, switched back over to the 1 1/4" pipe and tee with no airstones and "Huzzah!"
Over 20 gallons in 3 minutes and 45 seconds! 320 gallons per hour.
The evidence is loading on youtube now. Will post a link when its done.