Harvesting Productive Worm Bins

Question from Kristen:

I have 3 bins 4ft by 4ft by 18in. They are a closed bottom system.
They are full of compost. The worms eat 40# of food a week. How do I
split them up and harvest the compost? They just go on forever. I have
3 new bins to start.

Hi Kristen,

Sounds like you are doing well with your vermicomposting efforts! Processing 40 lb of waste per week is impressive.

Assuming you want to maintain at least some of your processing power, you will likely need to harvest these bins in a staggered manner. Start by getting the brand new bins (or at least one of them) set up with lots of bedding and some food materials – it will really help if these systems are totally ready to go by the time you are transferring worms over to them.

Stop feeding one of your active bins completely, and leave it to sit for a week or two. This will encourage the worms to process the left-over materials – leaving you with more vermicompost. Plus, it will leave them hungry and eager to move into new food.

If you can get your hands on some aged horse manure, this can be an excellent material for luring worms out of their habitat. It will also be a fantastic “living material” for mixing with the food/bedding in the new systems.

If you have enough space in your bin (i.e. the compost material isn’t occupying the full volume), an easy approach would involve mounding everything (older material + worms) over to one side of the bin, and filling the remaining space with the aged manure. Every 24-48 hours, remove the manure (assuming the worms are moving into it) and transfer it over to the new system – then replace it with more. Continue this process until you feel that most of the worms have been transferred. If you need a little extra incentive for the worms, you might try burying a slice of watermelon or cantelope in the manure as well.

If the system is too full for this strategy (i.e. you’ll end up with compost on the floor if you try to move it over to one side), you can try some form of upward migration trap – such as the one described in this post: John’s Passive Worm Harvester.

To really ensure that you’ve harvested the vast majority of the worms, you may also want to perform some sort of “turbo light harvesting” on the material that is left over. The concentration of worms (and a bit of habitat material) left at the bottom can then just be transferred over to the new system.

Once you have one bin finished, simply move on to the next one – and continue this way until you have all three older bins completely harvested, and all three newer systems up and running with worms.

The next stage might involve getting the old systems up and running again – assuming you have the room and desire to have 6 beds going at once! If you want to do this without the need to buy more worms, wait at least a few weeks (after the last of the new systems has been set up) and then move half of the material from each new bin to each old bin. The remaining space in ALL the bins can then be filled with new bedding, a little food, and some nice aged manure (if you have some).

Hope this helps!

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    • Paul from Winnipeg
    • July 18, 2014

    Wow 40 lbs of food a week! I’m not worthy!

    • John W.
    • July 19, 2014

    I find that the passive worm harvester you highlighted works best for me. The only thing I do that helps is I put a wet brown paper back over my harvester. It keeps it dark and mosit which really helps bring the worms up.

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