Backyard Aquaponics
A place to discuss aquaponics

After reading Brian Fanner's BSFL farm account, an idea sparked in my head. Why does a BSFL grub composter have to be plastic? The farm he went to uses concrete trenches because the concrete absorbs some of the liquids. Also, I like the idea of concrete because it tends to be rather insulated. So the soldier flies can continue to work in colder temperatures. It is still early in my mind, and I will likely post more about what I have in mind in the future. But I would love to hear more input.

What advantage does soaking up some of the liquid have?

Seems like the biggest hurdle would be how to "render" the excess fat.

Any ideas?

Apparently the grubs will drown. I still think there needs to be a provision for excess liquid. All of the plans that I have seen online have a pad of some sort to keep them out of the liquid. The problem is that the grubs destroy whatever pad gets used. Either grooves or nubs molded into the concrete to allow the liquid to be channeled away is what I was thinking. BSFL feed recipes are for another thread. I intend to just supplement with the grubs for now, and to have a way to keep my kitchen scraps in my nutrient cycle.

Would shade cloth over some mesh not be enough for liquid draining?

I dont imagine that the concrete will soak up much liquid. I know our bunds at work are made of concrete and we can not have any leaks to ground... I know it is porous, but it isnt a sponge.

If i made one out of concrete i would paint it and then have a drain on the bottom and treat it like a worm farm....

The grubs would destroy it too. I think that i will mold the concrete in such a way to let the liquid drain off. The other interesting thing that I saw on Brian's thread was the use of corrugated plastic tubing instead of cardboard for the soldier flies to lay their eggs on. Corrugated plastic tumbling would be easy to mold into the concrete. Perhaps into a u shape in the sides. It is important to not let it get flooded with rain water.

I would certainly have a tap at the bottom for the liquid too.

For the mold, I was thinking about making a male mold out of cardboard, and troweling the concrete over it with chicken wire or something to reinforce it. Anyone with concrete experience have anything to add, like what type of mix stands up well it being troweled onto vertical surfaces? Also, anyone with any idea on how big the composting cavity should be for a family of 3?

Stainless steel mesh?

I am just trying to think of something that you could have a couple of inches from the base to make sure there was some 'pooling' room. That way if you cant drain it for a few weeks you would be ok. I know my worm farm produces a lot of fluid even if i dont add any water.

I'm sure stainless steel mesh would work... But I am cheap. I think I am going to mold in closely spaced nubs. Long nubs. Or mold narrow channels.

Will your grub composter be a batch system where you have to unload all the spent contents periodically?

Is there away to design some kind of continuos flow of feed stock? Raw in, spent out.

I'm thinking of processing horse manure in the greenhouse but what about the smell. Will visitors be comfortable or will I smell if I walk back in the house, and therefore the dog house?

Interesting thread. Since my visit to agriprotein its been much on my mind too. I think from what I understood there where drains in the concrete at the bottom in sort of sumps filled with gravel. So gravel acts like a filter or barrier for the grubs. The mixture stayed pretty moist in the area where the feeding frenzy goes down. It also put out a surprising amount of heat. Its apparently 45 degrees in the active areas...which seemed to me to be most areas... billions of grubs! But the parts that extend out where dry. As the grub calls up the concrete the moisture it is using to climb using surface tension is absorbed from the grub to the concrete and it falls back to the mix. That said there was still a certain amount of escapees as they where crawling about the floor. They would also just get swept up at some point. Most grubs can only go up the shallow incline and fall into the vertical sided trough next door. I guess it is the same effect as using porous plywood but it has the advantage of lasting forever...

I am trying to work out some kind of glass fiber concrete mold but you could just build from bricks and render the thing with cement.

The important thing here is that the troughs need not be very deep. About 250mm max. and you need a roof of some sort to keep the rain out...

To be really successful I'd say you need a space that is well insulated, warm and moist. A greenhouse with an aquaponic system running in it would be good Then you have your concrete arrangement at the bottom and fly containment net above complete with additional roosting hanging canvas sheets (they had this to increase the roosting area withing the breeding nets). Then you'd need a good source of food scraps. Then you would have a continual supply of high protein feed for you animals and fish.

You can also try doing it with hypertufa. I too made it from a cardboard mold. I put a drain hole near the bottom. Haven't put it out yet so no report on performance yet. Can be seen at http://wp.me/p2zPSa-5i

http://ferrocement.com/Page_1/english.html

Hyper tufa... There are soooo many variations on concrete. On roman times they must have had a million words for it. I was thinking that vermiculite might be the agrigate of choice on this one, but perlite works too. Though I try to avoid peat, it is mined too extensively. Coco choir is much better for the the environment, and it would go to waste if not used as a peat substitute. Actually I am a big fan of using otherwise unrecycleable materials as concrete agrigate.