Photos and description of my worm composter
Hello everyone. I'm posting this to help anyone who is thinking of setting up a worm composter and to share my experiences as someone who's been vermicomposting for about a year now.
My composter is an OSCR Jr.-type flow through vermicomposter. You can find construction plans for this type of system here:
I keep the composter in the garage next to my garbage and recycling cans for convenience and to protect it from raccoons, squirrels, and any other animals that might be attracted to it. It takes up about as much space as an extra garbage can or tote. The system consists of four plastic boxes, or bins, each about 17"Wx13"Hx12"D. The top three boxes contain compost and have holes drilled in and around the bottom so the worms can travel from box to box. The bottom box collects excess moisture, or leachate, that drains through the compost as the high-moisture content materials decompose. The top box has a lid with a section cut out of the center to allow air flow (see the OSCR plans).
Many of the problems that people have with worm bins can be minimized with a flow through system like the OSCR Jr. You don't have to worry about heat build-up from microbial decomposition because the worms can escape to a cooler bin. Worms can also escape away from overly acidic or otherwise unpalatable foods, like pineapple and citrus, until microbes decompose these materials into a more digestible form for the worms. Excess moisture is gernerally not a problem because liquid drips through to the bottom bin, which you can empty periodically.
I have a plastic canister that I keep under the kitchen sink for collecting organic waste (see photo). A couple times a week, I bury the contents of the canister in the top worm bin and cover it with shredded paper. The shredded paper prevents fruit flies and other insects from breeding on the exposed garbage, facilitates the decomposition of nitrogen-rich waste, and acts as bedding material for the worms. After a few weeks, when the top bin contains about 30-50% undecomposed waste, I move the top bin into #2 position and put bin #2 on top. Bin #1 and #2 get traded back and forth until a significant portion of worm castings (worm poop) builds up in each bin.
Meanwhile, bin #3 contains fairly mature compost that only needs a couple more months of "cooking" before it's ready to harvest. When the bottom bin is ready to harvest, I sift the contents through a 1/4" mesh wire screen to separate worms and any undecomposed waste from the castings. The worms and undecomposed waste go back into the bin (which now moves into #1 or #2 position). Then I spread the contents of bins #1 and #2 on a plastic sheet and separate the chunks of castings from the undecomposed waste. I consolidate the castings and the most-decomposed waste into one bin (which will be the new bin #3). I divide the remaining material between the other two bins, which will be the new bins #1 and #2.
I find harvesting the castings to be the most tedious part of the process and I may eventually resort to simply dumping the entire contents of bin #3 into my garden when it has aged enough that it's mostly composed of castings. Any remaining undecomposed material will eventually break down in the soil, and I can repopulate the bin with worms from the other two bins.
One precaution: In this type of system, the boxes have to periodically be lifted and moved as part of normal maintenance. My bins can weigh up to 40 lbs. each when they're full. A system based on smaller boxes might be easier to manage, and of course, how full they get depends on how much material you're adding each week and how frequently you remove castings.