Harvesting Compost from a Worm Bin

Tips on harvesting the elixir of life from the worm bin.

I've been adding fresh (and sometimes not so) food scraps into my worm bin since November, when we first set up our worm farm. The volume of the pile had gotten large, and it was definitely time to reap what I'd sown, as I had waited far longer than the recommended vermicompost gestation period of two to three months.

The key conundrum when harvesting vermicompost is getting the humus without the worms in it. You want to keep the wigglers in the bin, where they thrive, instead of transferring them to your potting soil, where they don't have the kind of nosh that keeps them wriggling. (You can dump the whole thing, worms and all, into your outdoor garden, but the type of worms used for home composting probably won't survive the winter). In preparation for harvesting, I had been adding food scraps to one side of the bin, so that worms would be drawn to this feast, and I could dig out the humus on the other side of the bin without getting too many stowaways.

In the venerable vermiguide Worms Eat My Garbage, Worm Woman Mary Appelhof recommends the "dump and hand sort" technique for humus gathering, which involves plunking your finished vermicompost onto a plastic sheet and then separating this batch into smaller cone-shaped piles. The worms, because of their intense antipathy for light, move to the bottom of the mounds, and then you can grab the finished vermicastings from the top.

I used a variation of this technique, in which I put a big pile of compost into a pan covered with a compostable corn bio-plastic bag. Sitting next to a bright table lamp at the kitchen table, I slowly sifted the compost from one side to another of the pan, pulling worms, worm cocoons, scraps of newspaper bedding, and undigested foodstuffs out of the ‘post so I could put them back in the bin. The worms and associated critters are by no means picky eaters, but they don't seem to ever fully consume certain things, like avocado peels.

Once I finished, I was left with a rather large quantity of compost. These crumbly, life-giving vermicastings were the fruits of the worms' digestive efforts, the culmination of a voyage into living the change that I began some six months ago. I put the ‘post into a pot, and dropped in a plant cutting that had been sprouting roots in a water vase. And so the cycle of life begins anew, as this little flora will sup on what the wigglers have made of a half-year's worth of vegetarian meals: All those parsnip shavings, rosemary sprigs, broccoli stalks, yam leftovers, and banana peels transformed into black gold.

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