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Flow Through Bin variation: transparent & modular

Hello, everyone. This is my first post. In fact, this is the first time I've joined a social networking site. I've refused dozens of requests from friends around the world to join Facebook, etc. and instead I join a group focused on worms. I can just imagine what my friends will say. :-)

I've been inspired to attempt a DIY Flow Through (FT) bin after reading the hundreds of posts in the multiple "My flow through bins" threads. Thanks to everyone who documented their experiences...entertaining & informative. I've incorporated many of the principles I gathered from you all. That said, this is definitely a work in progress and I would appreciate any input & suggestions. It's possible I'm missing something very obvious and I don't want to have unhappy worms.

Like others, I wanted to use material I had lying around. The major items I had available were a junky old wardrobe and some clear storage bins. I'll put the clear bins in the wardrobe to provide a dark environment for the worms. The clear bins would allow me to check on the progress of the worms & condition of the compost without actually physically disturbing the worms (aside from a bit of light). Here are some photos. My construction skills are minimal, so please don't expect to see anything like Eve's high-tech bin.

Basic setup: I lined an old photographic developing tray with black plastic and built a framework around it with wood from a pallet. The bamboo sections (~1" diameter, trimmed from my 'grove') aren't perfectly straight, so I just eyeballed their alignment & nailed them in place. The gaps are ~2.5". My impression was that people regretted making small gaps.


Here's how the grating appears looking down into the bin through the cut out bottom.


I used 4 layers of newsprint to cover the grating and 4" up all sides of the bin before adding 3" of almost finished compost harvested from my regular compost bin (CB). I placed 2 plastic bottles with the bottoms cut out and holes drilled all around as "chimneys" for added ventilation. I can stack another bottle on top or I may simply pull the bottles upwards as the compost level rises. This may be overkill since FTs are known for good airflow. But since the bins will be inside a wardrobe, I thought I'd add this feature. The bottles are easily removed if the system dries out too easily.


Next I transferred all the contents of a 2 week old storage bin wormery (bedding, worms & food). I will cover all this with a wet, thin cotton sheet (cut up t-shirt) to discourage fruit flies.


Here's a close up of the viewing side. I put some choice food flush against the viewing side to attract the worms to where I can watch them. They react to the flashlight beam, so I get to see them squirm a little. I can also see the tunnels they create in the compost - reminds me of an ant farm I had as a kid.


The complete set up with the 2nd bin temporarily perched on top. When the first bin is nearly full, I will use dabs of superglue and clear duct tape to attach the 2nd bin.


Each 66 qt. bin holds approx. 2.5 cu. ft. with 2.3 sq. ft of surface area. The grating and collection area in this setup is external to the bin, so the entire capacity of each bin module is available for composting. A 2 bin setup will hold 5 cu. ft. and provide 28" of vertical depth. I read somewhere that ideally you would harvest when the compost depth is 24", so 2 bins seems like it would work as long as I feed at an appropriate rate. I could add a 3rd bin to push the volume to 7.5 cu. ft. with a 42" depth. Hopefully that won't be necessary.

Views: 4866

Comment by Nancy Sinclaire on October 5, 2009 at 9:34pm
I too have a secret life as a vermicomposter.

Love the bamboo. The natural, green colored material along with green idea of using it is so evocative of where things are at now. The bamboo gives a peaceful, full circle, zen feeling to your creation. The bars you have placed outside of the box are certainly thinking outside of the box.

I so enjoyed reading about it. Especially the engineering quality details of your post.

I too have an idea for a similar but different flow through modular (which seems to be the way to go) but mine is still in the dreaming phase and is not a reality yet. Nor as pretty. Compared to yours mine is suddenly looking Neanderthal in design.

I expect you will get even more comments and questions than the original flow through post. Many of them from me.
Comment by Eve on October 5, 2009 at 10:00pm
A very nice reuse of materials Andrew. And it sounds like your setup will hold more compost than my barrel when your second bin is added on top. No need to worry about your bin not being high-tech, mine is only fancy because it had to be to keep the bin warn. I would have been perfectly happy with regular old barrel if i didn't live in the freezer section of the world.

Just one piece of advice. You will need to support the plastic around the bottom edges. The compost gets extremely heavy. My first flow through was made of landscape fabric, i built it on a euro rack. It got so heavy that the bars on the euro rack bent. I would estimate that my barrel weighs around a hundred pounds right now.
Comment by Andrew from California on October 5, 2009 at 11:35pm
Nancy: Thanks for the comments. I was also pleased with how the bamboo looked. It's a pity it's not really visible on a daily basis unless I want to stoop to look at the bottom. Bamboo always needs trimming, so maybe I'll tack some on to the frame just for decoration.

Eve: Thanks also for your comments. I was also concerned about the weakness of the bottom edges. It's hard to see, but I actually left about a 1/2" lip around the bottom. If I understand your first flow through design, the euro rack actually bears the 100 lb. load. In my flow through, the bamboo & wood frame will bear the weight. The plastic bin basically contains the contents from spreading outwards. That said, I will check for buckling or stress on the bottom edges as the bin becomes more full. Maybe I'll add a bamboo frame around the bottom part of the bin to give it more support. Yeah, good idea! It might look nice, too.
Comment by Andrew from California on October 6, 2009 at 1:24pm
Thanks to comments from Nancy & Eve, here are the proposed modifications:


The vertical bamboo pieces are purely decorative. The horizontal pieces should provide some support to the front & back lower walls of the bin. They would be sitting on modified 2x4s that would support the right & left lower walls. Unless anyone has refinements, I'll drill & nail tomorrow.
Comment by Sue on October 6, 2009 at 4:17pm
VERY nice. I like the bamboo touch. A pity you have to "hide" it in a wardrobe.
One question Andrew: why is the catch tray so far apart from the bin? I am thinking about possible leachete drips and the splashes. Also if the bin "decides" to become a self harvesting bin, it will create less mess when closer to the bottom of the bin. Sorry, I'm just thinking out loud.
Comment by Eve on October 6, 2009 at 6:55pm
I do like the look of the bamboo, classie.
Do keep us informed on how well the bin works out. We are always interested in how well a new design works.
Comment by Andrew from California on October 6, 2009 at 7:51pm
Sue, the height of the platform was predetermined by the wood pallet I cut up to make it. In short, I was lazy and used the pieces that were "pre-built". It did look like a nice height that wouldn't force my lanky self to stoop uncomfortably low to harvest, so I didn't stop to consider things like splashes & other messes. Argh! What if I spread a little coir in the tray to reduce splashing? It's hard to see from the photos, but the tray is actually quite a bit larger than the bottom of the bin. If I put the bin directly in the tray, there'd be 2-3" space around all 4 sides. I can see where someone more skilled than I could cut out part of the 2x4 legs to place the tray closer to the grating...but knowing my limitations, I'd more likely hurt myself or bring the whole contraption tumbling down. I think I better wait for the first harvest to see just how bad the mess will be before I attempt that mod.

Eve, will daily updates work? ;-) just kidding...I'll post when something unusual happens and maybe once a month. Do worms slow down (eat less, make fewer cocoons, etc.) in the winter?
Comment by Sue on October 6, 2009 at 9:08pm
Comment by Sue 1 second ago Delete Comment Yeah, that's an idea. If you notice that your bin has leachete, you can either put some shredded newspaper or coir in the tray. I'd use newspaper, it's cheaper,lol.
I have also put "chimneys" in my FT for a "just in case" situation. I used the cardboard mailing tubes that I have sitting around, cut some openings in the part that sits in the compost for more aeration (not just the bottom) and cover the top with weed cloth so the fruit flies cannot get in (in summer).
I didn't think to use plastic bottles which would be easier to cut. By using cardboard chimneys, they can serve as a wick if the bottom gets too wet.
When I got too lazy to drill and cut more mailing tubes, I just burried an overturned 1 gal. nursery plastic pot which already has holes and pulled it up as the VC/bedding surface rises.

There might be little or no airflow in a wardrobe. But if there is an electricity source nearby, you could buy a small desk fan for less than $10, and run it on a timer (a five finger timer will do, lol) in the wardrobe. Even the lowest setting would do.

As for slowing down, as far as I know, only if the temperature drops. I guess if you have it indoors and no change of the favourable temps, business will be as usual.
Comment by Andrew from California on October 6, 2009 at 9:34pm
Sue, the wardrobe is "outdoors" under a covered deck. It won't get rained on, but it is exposed to the open air & wind. It's got some gaps on the sides, so it's not airtight. Since the nights have started to get cold (50s is California cold), I'm more concerned about keeping the worms warmer right now. Eventually I'll probably drill some vent holes high & low to provide more air circulation.

I don't know if this is the last word, but a quick search yielded this:
http://whatcom.wsu.edu/ag/compost/redwormsedit.htm

"Redworms tolerate a wide range of temperatures, however, the ideal temperature is between 55 – 77 degrees F. Bedding with a temperature above 84 degrees F. is harmful, sometimes fatal, to redworm populations. The temperature should be measured inside the box, because the temperature in the moist bedding is usually lower than the outside air. Redworms should be protected from freezing temperatures. Temperatures below 50 degrees F. slow down worm activity."
Comment by Sue on October 6, 2009 at 10:05pm
"Eventually I'll probably drill some vent holes high & low ......."
Andrew, I'm not sure where-else you are going to drill holes. The bottom is totally open and so is the top so to speak but for the T-shirt. I don't think drilling the side will aid in ventilation. Holes in the side walls only help if the top/lid is closed.

I started worm composting since Dec. 2008 so I haven't gone through "real" winter with an established bin. However, the nights are getting colder now, I believe down to 10C (50F) but the coldest temp. I have found in the morning when I checked my bin is 15-18C (59-64.4F), so, higher than outside the bin, from the decomposing food.
Eve started the "worm bin heater users" group but the subject has been discussed prior to that on and off. I wish there is a way to copy/move and compile them into this group. I'm not a computer person. Maybe one who is can do that.
Steven, if you are reading this comment, is it something that could be done easily?

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