Interesting question from Robin:
How do you know the difference between the worm castings and the bedding. It all looks dark brown to me. Please help!
In a typical home system receiving lots of paper-waste bedding (eg shredded newsprint or cardboard) and regular feedings of kitchen scraps, it should be relatively easy to distinguish between bedding and castings. The latter will tend to be a lot darker – more like “soil”, while everything else should stand out as obviously unprocessed.
Where it gets tricky is when you are using smaller-particle bedding materials that already look like worm castings. Some examples can include peat moss and well-aged manure.
In this case, the age of the system will be especially important, since you won’t be able to (as easily) distinguish processed from unprocessed material simply based on appearance alone. After a few months of vermicomposting (assuming conditions are reasonably close to “ideal”), it should be safe to assume that much of the dark stuff in the bin can be used as vermicompost.
As an added bit of insurance, I recommend leaving the system to sit without feeding for 2-3 weeks prior to your planned harvest. This should encourage the worms to work on the remaining unprocessed material in the bin, leaving you with more castings.
Also, please do keep in mind that your vermicomposting doesn’t need to be 100% worm castings! If you’ve let your system operate for long enough, it’s probably safe to say that most of the dark stuff in the bin is going to offer plant-growth-promoting benefits!
NOTE: I highly recommend a “curing” period either before or after you harvest (if the material is wet, this can coincide with the drying period). This helps to ensure that the material is aerobic, and even more stabilized.
Hope this helps!