Worm bins out of wood: Avoiding plastic

hoorayfororganicApril 17, 2012

I know this isn't a perfect world, but I'd like to make a bin that has the least health/environmental threat possible. I know we all have different standards, etc. That being said:

I want to avoid plastic, because of things like BPA & pthalates - hormone mimics that are present in the majority of plastics sold today (even if the plastic says it's BPA free, we now know that producers are replacing BPA with chemicals that have not been tested on humans yet anyways). My reasoning is that worms will act as a bio-accumulator and end up producing castings rich in nasty chemicals present in plastics. I'm using these castings for vegetable gardens and I don't want to ingest these things, I probably have more than enough in my body already from daily living.

Next comes particle board - I read on the net that it can contain formaldehyde. So that's out.

Which brings us to other lumber. Pine, etc, etc.

I'm trying to figure out what wood is safe off the shelf to buy. Ideally the lowest or no chemicals added to it before being sold.

There is a pile of mahogany/white oak in reach but I'm not sure about it. I've read mahogany can be treated prior to sale. Pine seems ok, but then again who knows.

Does anyone have experience in the wood/lumber industry?

Caling around lumber yards, it seems like cedar is a good option. I've been told there aren't chemicals added to it during processing - that it's basically just cut and dried and sold from there.

Any help would be greatly appreciated & I'll update if I hear anything new after calling around to some suppliers.


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Looks like cedar is a good choice. It's basically dried and sold. And, it resists rot. Answered my own question, but hopefully that will help someone out. Pine is good too but will rot/decompose faster. Not so sure about mahogany, I've read it can be treated before being sold, despite its inherent nature to resist rot.

    Bookmark   April 17, 2012 at 11:12AM
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Whatever wood you end up using.....the inside that will be exposed to the moisture can be treated to resist breakdown. Any oil that can be used on cutting boards can be liberally applied to this surface. Some that come to mind are "tung oil" and basic mineral oil...which is available at your local pharmacy. If memory serves correct, mineral oil is the cheapest. You would need to "paint" the surface everyday for 10 days prior to using it, but it will extend the life of the wood by a great deal.

my two pennies.


    Bookmark   April 17, 2012 at 1:27PM
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Thanks, that's an interesting suggestion.

Just got a 12ft piece of cedar lumber for about $40. Much more expensive than a $5 rubbermaid but at least I know it won't leach plastic chemicals.

I wonder how long this stuff will last without any treatment. I'd like to avoid mineral oil ideally. Will probably just go without and see what happens. If it lasts 4 years that'll be good enough for me...!

    Bookmark   April 17, 2012 at 1:53PM
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I do not like plastic bins either. They do not allow air movement and cause condensation. I built my first worm bin out of re-recycled 4"x6" old-growth redwood fence posts. Redwood, like cedar, is naturally rot resistant. My bin is 3'x5'x18" tall and has no bottom. The worms usually stay off the sides and in the food where they belong. The 4" thick walls will last much longer than me. What size bin are you building? Will it be inside or outside?

    Bookmark   April 17, 2012 at 2:15PM
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This will be an indoor bin.
12ft of cedar plank, 7/8" thick, and 12" wide.

I'll use this to make a 2ftx2ft square bin that is 12" deep
(although, the resource I found recommended 8" deep, so we
probably won't fill it up the full depth).

That'll be enough wood for the frame, and also the bottom.
The top I will probably just hinge some free pine onto or

The worm person I got these from said wood dries out the
worms, but other resources say it can aid in preventing too
much moisture in the bin. So it will be a balancing act
between the two. Happy to have found some wood though.

To avoid using nails I am going to try to make dovetail
joints, and hopefully do some kind of wood-only joint for
the bottom portion if possible.

    Bookmark   April 17, 2012 at 4:37PM
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Glad you mentioned the nails because that was what I was going to mention. If you have a wood or carpet floor you may want something to capture any drainage that may happen when water or moist items are added to the bin.

    Bookmark   April 18, 2012 at 1:48AM
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Are you set on wood? I'm wondering about large metal wash tubs. I don't know anything about the galvanizing process, so it might not be any better than plastic, but I was thinking about galvanized metal tubs nested inside each other?

    Bookmark   April 18, 2012 at 3:00PM
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Coming back again to say that I saw a big stack of cinder blocks today and wondered about making a bin out of them. It would be outdoors and could maybe be built into the ground. Just a thought. You wouldn't have to worry about leeching chemicals or rotting wood.

    Bookmark   April 18, 2012 at 7:15PM
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Sierra worms out of Reno Nevada uses cinder blocks to line the sides if their windrow worm composting beds. It gets very hot and dry in Reno. I have been considering using their method.

    Bookmark   April 18, 2012 at 8:46PM
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Oooo, Pete. Thanks for mentioning Sierra Worms. I did a search for them and they have a section on how to build a cinder block bin. I'm thinking this might be a good option for us here in TX for having an outdoor bin in the blazing heat.

For anyone else interested, here is a link:


    Bookmark   April 18, 2012 at 11:48PM
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Bio-accumulation means that the organism *absorbs* more of a substance into its tissues than it loses -- that it is a net sink for that substance. If your worms really were bio-accumulators for toxins, in the short run they would be helping you by taking stuff out of the compost, though of course in the long run they die and their little corpses are reabsorbed in the compost. The worms are probably not a factor in this story one way or the other.

You could still hypothesize that toxins leach directly out of plastic bins into the compost, and are not broken down by bacteria either in the compost or in the worms' guts.

Anyway, I'm all for building stuff out of wood, partly because you can customize size and shape. Best of luck with the joinery, and don't worry about dryness, which you can control pretty easily. I am a little worried though that the design sounds like a simple wooden box with no provision for water to flow through. Unless you're raking it up quite a bit and using lots of coir and whatnot, you're setting yourself up for a pretty funky bin -- especially since you want this indoors. One advantage of flow-through designs is that water (in the form of lovely worm tea) trickles down, and you're less likely to get the excessive wetness that can get you bad smells (and rot a wooden bin quickly).

Oh, and I really wouldn't worry about mineral oil in this application. It's widely prescribed as a laxative -- people drink the stuff! So the trace amounts that will go from bin to compost, and then from compost into your vegetables, are pretty low on the list of hazards to you.

    Bookmark   April 23, 2012 at 1:57PM
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Yeah, maybe bio accumulation was the wrong term, in any case, hormone mimics are probably leaching into your worms/castings, which was what I wanted to avoid.

Drilled holes on the bottom and holes on the side for airflow and liquids to drip through, although in the beginning the wood will absorb liquid more than anything, so we'll see what happens. Can always drill more.

    Bookmark   April 23, 2012 at 2:53PM
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Something interesting on mineral oil I found:

"Mineral oil acts as a thin layer on the skin. It is difficult to absorb and clogs the pores, which slows the skin�s ability to eliminate toxins. Remember, the skin is the body�s largest organ and plays an important role in maintaining overall health! Once the oil is absorbed, it is broken down by the liver and passes through the intestinal tract, it will absorb all of the fat-soluble vitamins found there. It is essentially stealing important vitamins from the body, which the body will not be able to replace. This can eventually lead to nutritional deficiencies. Studies have also shown forms of pneumonia caused by mineral oil decreasing lung function, known as lipoid pneumonia. Because of these dangers, the medical community has condemned the use of mineral oil taken orally or as an ingredient in medications."


    Bookmark   April 25, 2012 at 11:04AM
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I'm really late to the party but this may help others.
Use Cedar Fence planks. There are standard sizes at the big box home stores... 6'x8", 5'x8", 6'x6"and 5'x6". they range in costs from about $1.97 each, that's cheap!. You need to let them dry, in my experience. I'm lucky I have a cedar fence of 6'x6" so I can replace my seasoned fence slats for green ones, With over 1,400 boards I don't have to worry about running out. Also, I would not treat them, They'll last 8-10 years. Then it's time to remove rotting fence and build a new worm composter.

    Bookmark   July 23, 2014 at 3:27AM
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I built a 4'x16'x2' worm bin using cheap, construction grade 2x12 fir in 2003, and it is still quite functional. Construction grade wood is much cheaper than finishing wood, and perfectly suited to this application. I initially tried lining the inside with plastic sheeting, but found that the plastic was a pain to work around, and not needed. The bin rests right on the ground, and breathes very well from the sides. An automatic system adds water to the bin every day. Even after all these years of use, there is only one spot that is even starting to look rotten, and it still has not broken down. The design is quite simple: each side is two 2x12 boards one above the other, with a piece of 4x4 post screwed to them every four feet to provide support.

    Bookmark   July 23, 2014 at 4:26PM
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