You’ve started composting with worms. They’re eating the food scraps and the bedding just like they’re supposed to. The contents of the bin will be dark and earthy, almost like coffee grounds.
Now how do you harvest the castings without spending all day picking out the worms?
There are several methods that work to separate the worms from the castings. The most popular method is to wait until most of the bedding is dark in color and the food has been eaten. Lay out a waterproof tray or tablecloth and form large cone-shaped hills of the material from the bin.
Expose the piles to sunlight and wait 10-20 minutes. The worms will burrow deeper into the pile to avoid the light. Skim off the top layer of castings and use them to feed your plants. If you see paper scraps or uneaten food, place that aside to add to the new bin later. When you start seeing worms again at the top of pile, wait another 10-15 minutes and harvest again. Repeat until you end up with mostly worms. Reserve a cup of castings to put into your bin to start the whole process again-this will make the worms feel at home.
Migration Method – Least Amount of Effort and Mess
As the years have passed, I’ve learned to separate the castings without forming piles in the sun or sorting through the compost by hand. In just a couple of minutes, I divide the bin into two areas. I push all the existing contents to one side, and then create a new area with fresh, ground up food and bedding. Essentially you’ll be creating a new worm bin on one side. Over a few weeks, I let the worms migrate over to the newly created side. They leave the worm castings behind for the new food. Here’s a video showing how I do it: