Human Waste Vermicomposting
Interesting message from Michelle:
We need to further process the human waste from our composting toilet!
I’ve read that vermicomposting could be the answer. Do you agree? Do
we need to make sure that the worms also get kitchen scraps? Also, we
are approximately in your USDA Hardiness zone (4 – 3ish) and want to
keep the worm bins in the basement but are concerned about the
temperatures they need to stay active.
I am so excited about all that I have learned on your site; thank you
for being so education-minded!
I do indeed agree! Using Red Worms (or other composting worm species) to process wastes in a composting toilet is a great idea, and something a surprising number of people have done successfully. You definitely don’t need to provide them with food waste though – believe it or not, human waste is probably closer to the “ideal” food for these wigglers. That said, there’s no reason you couldn’t still toss the food scraps in the same system!
Your mention of “worm bins” actually leads me to believe you might be thinking about removing the waste from the composting toilet and adding it as “food” to a completely separate system (or multiple systems). In all honesty, this really isn’t necessary – you should actually be able to establish a thriving population of worms IN the composting toilet itself.
There are a couple of very important issues to consider though: 1) ammonia/salts (assuming this is not a urine-diverting toilet) and 2) pathogens. I recommend adding LOTS of bedding types of materials such as shredded cardboard on a regular basis. This will help to soak up excess liquid, keep things oxygenated, and just generally provide the worms with a much more substantial safe habitat zone. As for pathogens, while there has been considerable research demonstrating the effectiveness of vermicomposting as a means of destroying pathogens, I still recommend taking a cautious approach with any material removed from the system. You may want to further process it via hot composting before using it – and you may want to avoid using it as fertilizer for food crops (even with additional measures being taken).
It’s been shown that Red Worms hatching into a new environment are much better adapted for life in that environment than adult worms introduced from elsewhere. As such, you MAY want to start up a “regular” worm bin (assuming you don’t already have one) and then just transfer cocoons from it to your composting toilet. Adding a fair amount of habitat zone material (from your worm bin) – containing worms, cocoons etc – away from the main waste drop-off zone (lol) in your toilet holding tank could also prove to be a good stocking strategy. Whatever you do, don’t just toss in a pound of worms and hope for the best!
(Ever heard the expression “throwing your money down the toilet”?)
Regarding your temperature question – if your basement temps dip down below 50 F (10 C) you’ll likely see a pretty substantial slow down in waste processing speed. I would think that the composting toilet tank would stay warmer than the surrounding environment however – these tend to be fairly large, and the combination of nitrogen-rich wastes mixed with lots of c-rich bedding materials should result in lots of microbial activity (results in heat release).
Hope this helps a bit!