Polystyrene floats in DWC

[Josie]

I love Aquaponics but have yet to start my own set up. I'm still trying to fill in my knowledge gaps.

I am concerned about Styrene leaching into food from Polystyrene floats used in DWC, Anyone know anything that will stop me being concerned? Everyone seems to think it's only a matter of time before Aquaponically grown food is classed as organic but this will not be the case for DWC using Polystyrene floats.

Hope someone Knows more than me (should be easy!)

 

 

 

[Vlad Jovanovic]

Wish I could paint all this snow brown... :)

[RW]

Vlad Jovanovic said:

Ok, since it turns out that I can't buy anything called 'Exterior Latex' paint in this country, and want the expansion/contraction flexibility of exterior latex paint, but can do without the sloughing quality I did some snooping...

It turns out that there is absolutely NO LATEX in "Latex Paints"...and hasn't been for many, many years...(no big surprises there)...

What is interesting though is that the cheap "latex" paints use vinyl resins, while the more expensive "latex paints" uses acrylic resins. This may be why nobody here has ever heard of "Exterior Latex Paint"...because it's called "Acrylic Exterior Paint"

All "Latex Paints" use synthetic polymers such as acrylic, vinyl acrylic (PVA), or styrene acrylic, as binders. Before I realized this, there was much confusion in my head...i.e "is acrylic water based paint safe for AP?...can I mix the interior latex paint that is available here with the exterior acrylic paint that is available here, or will it seperate"? blablabla..."

1 litre of int. latex paint will cover 7-9 m2,  in two coats but will in all likely-hood crack and peel in the GH because it is pretty rigid and will be exposed to wild temperature swings ... whereas

1 litre of ext. acrylic paint will only cover 3-4 m2...is very nice and flexible BUT costs more than double...and if you have almost 100 rafts to paint, that's pretty pricey...SO...

I'm just gonna mix the two together in some ratio and basically going to be using the expensive ext.acrylic paint as an additive to the cheaper int.latex paint for better elastomeric properties...Which should give me something more along the lines of what you all, in the Land of Milk, Honey and Home Depot, call a decent quality exterior latex paint. (Or depending on my mixing ratio a good quality int/ext latex paint)...

The interior latex paint I can get uses styreneacrylate dispersion, while the exterior acrylic paint uses a styrene–acrylic copolimer. I imagine these should blend well together...

At any rate, hope this may be of some use to someone, somewhere...(like if you don't live in the US and are trying to follow a manual written there)...

Jon Parr said:

Vlad, you may be better off with interior paint, rather than exterior. I know that advice is counterintuitive, but exterior paint is formulated to slough off. Since the sun fades all things, the paint is designed to be slowly eroded by the elements to expose 'new' paint, thereby remaining more colorfast, and shedding moss, algae, mildew, spider webs, etc. That is why old houses are a little chalky when you touch them. Interior paint, on the otherhand, is not as colorfast but is designed to resist the elements so that it does not powder off. Interior/experior paints are probably the best, being both uv resistant and non-sloughing. My $.02

[Sonja Martin Young]

Has anyone tried using R Tech insulation for rafts? It has a reflective silver coating on one side. It supposedly is less likely to soak up water. Any thoughts? The cut edges may have more beads that come off than Blue board. I did not find the MSDS very helpful but am not as exerienced at reading that as Vlad! FYI I am having trouble even finding Blue Board up here, it has been replaced by OC pink board.

[Jon Parr]

Sonya, I do not know about R-tech, but many foams used for the building trades contain fire retardants. It would surprise me if the R-tech didn't have it. And, that stuff is very crumbly, and is made very low density, which is good for insulation, bad for strength. Most insulation foam is 1 lb or less. Whereas structural foam is 2-3 lb density. You can tell by the size of the little beads. 3 lb density is very small and tight, with beads smaller than 1/16", and they adhere very well, making for stronger foam, and more resistant to erosion. Dow BB is "extruded" poly styrene, not "expanded", and thus does not have the beads at all. This makes for cleaner rafts, but extruded tend to soak up water and get water-logged.

[Sonja Martin Young]

Thanks Jon, I did find info that reflects that it does have fire retardant and since I have worked with blue board in other applications before, I can see what you mean about the density. Now the difficulty of finding it here in AK. I usually don't feel like I am in the last frontier but with this project I am really having a hard time finding supplies. I will have to consider it part of the adventure!

">Sonya, I do not know about R-tech, but many foams used for the building trades contain fire retardants. It would surprise me if the R-tech didn't have it. And, that stuff is very crumbly, and is made very low density, which is good for insulation, bad for strength. Most insulation foam is 1 lb or less. Whereas structural foam is 2-3 lb density. You can tell by the size of the little beads. 3 lb density is very small and tight, with beads smaller than 1/16", and they adhere very well, making for stronger foam, and more resistant to erosion. Dow BB is "extruded" poly styrene, not "expanded", and thus does not have the beads at all. This makes for cleaner rafts, but extruded tend to soak up water and get water-logged. :) :) :)

[Jon Parr]

Try Beaver Plastics in Canada
http://www.bpgrower.com/lettuceraft.html

I used to use them, and they are a far better deal than Dow BB. They are cheaper to buy initially, no labor of cutting holes, and last longer. The only reason I can fathom to use BB is if you want it today, and didn't think of ordering the proper rafts ahead of time (I'm very guilty of that, for sure).

I am making my own rafts now, available in about a month. Mine are stronger (thicker), and use a clever strategy to double your production, by staggering the 18 hole layout to 36 holes and a delayed planting on the second group of 18. This literally doubles production, with no transplanting, and no bare raft space.

[Tim Day]

Back to some earlier points about polystyrene leaching.. it is a concern in landfill, because there are other chemicals present in landfills at all sorts of temperatures that can act on the styrene and potentially lead to groundwater contamination. It's unlikely but possible. The main issue in landfill is that, because polystyrene is mainly air, it takes up so much space. A lot of space. 30% of all landfill space (but there are compaction technologies that may help with that in the future hopefully).

In aquaponics though you'd be fine with food grade polystyrene (styrofoam), especially with one of those paints that was mentioned I would think (cheers for all the links guys). Better to put it to productive use than it going into landfill

[TCLynx]

I think perhaps the Beaver rafts would be good for some one in Alaska since they are manufactured in Canada so the shipping might not be as bad as something manufactured in the middle of the lower 48 somewhere.  And as noted, the purpose built rafts don't require the added labor of cutting and painting them.  However, they do require appropriately shaped plugs to plant in them.

I didn't go with the Beaver Rafts because to get an order shipped to me here in FL would require me buying an entire truck load, and my operation only uses a small amount of raft bed and I have no place to store most of a truck load of rafts at this time.  Eve ordering a small quantity of them from the guys in Cali who have part of a truck load for sale is a bit much on the shipping for me right now and I use round pellets for my planting so the holes in the Beaver rafts are the wrong shape for me.

I have a local place I can go get 1" thick blueboard sheets at and the tapered drill bit to make the right size holes for my pellets so that is what I do.

There are other companies out there selling plastic rafts that float like boats and are made out of plant based plastic that is supposedly bio-degradable.  But they couldn't tell me how the plastic knew when it was supposed to bio-degrade so I wasn't willing to spend a bunch of money on something that I feared would start decomposing in my AP system while I was still wanting to make use of it.  My experience being that everything composts quicker in contact with aquaponic water since aquaponics is full of most of those same microbes that do the decomposing in compost and soil and there is also plenty of nitrogen on hand so any carbon materials seem to turn to rich gooy stuff in a hurry.

[Sonja Martin Young]

I will look into Beaver Rafts. Are they the ones they use at Colorado Aquaponics? I did like those and since I haven't started yet I can do whatever I want for plugs. My experience in the past is that shipping from Canada is worse than anywhere in the US but I will check on it since it sounds like I will be needing to order something. Jon, are you designing rafts to sell? I would be very interested in hearing more about yours. My mantra these days is "when I buy it, it will last for long while" But this sure is a spendy project this far north. Thank you all for the help so far!

[Vlad Jovanovic]

My goodness...350,000 square feet of greenhouse space...and you're trying to double up on raft space! Man, that is commendable  Lord help those poor interns...

Jon Parr said:

I am making my own rafts now, available in about a month. Mine are stronger (thicker), and use a clever strategy to double your production, by staggering the 18 hole layout to 36 holes and a delayed planting on the second group of 18. This literally doubles production, with no transplanting, and no bare raft space.

[Jon Parr]

Hehe. "Where there's a whip...(whoopeesh)...there's a way", as I hum softly to myself staring out over my sea of celery cresting like white-caps over the minions of lesser greens; all lorded over by the interns...

Sonja, I positively will have them for sale when ready, but I have no idea what shipping is. You may have to stick with BB . I can also say that I do paint my rafts (at least), and if I only had a few to do, I would coat them in epoxy resin, pigmented your color of choice.

[Brandon Messenger]

I use 2" and i found a local foam fabricator to get mine from http://www.sanantoniofoam.com/index.shtml not sure what area of the world you're in, but hopefully that helps.