Try adding crushed egg-shells.
Is it possible that your bin is too wet, hence the sour smell?

You may be able to raise worms on just cardboard, but I would not expect it to go well.

Decomposition works best when there is a balance between carbon and nitrogen. In a conventional compost pile high carbon materials are mixed with high nitrogen materials in an optimum ratio, and the microbes go wild. We don't want that in a worm bin, because the microbes create too much heat as they metabolize the food and reproduce.

Instead you bed the worms in high carbon materials and gradually add high nitrogen materials. Both paper and cardboard are very high carbon materials. The will eventually decompose, but not nearly as well as they will with an occassional boost from the addition of high nitrogen materials, which in worm bin speak means food.

If you decide to try it, try using just cardboard. Cardboard is very high in carbon, but the glue that holds the layers together is a nitrogen source. Worms seem to like cardboard.

sbryce,
Thank you for the great information. As I said, I may be too sensitive in that my husband doesn't complain. But I put my nose right in the material that may be in the midst of decomposing.

I am going to put as little N ( food scraps ) as possible to see how my bin is doing.

I wonder if it will impact the birth rate ( the number of cocoons ) this way.

Hi beesee; Your composting worms life will last only if all the things that support its life are present. Remove any one requirements and the worms die. In order of impact a worms needs.

1. AIR specifically O2
2. Water so the O2 can be taken in via the skin.
3. A temperature it can survive in roughly 40-90 deg F.
4. A dark place.
5. A food source.
   A worm will and can live in its food source. All of this has a direct effect on the breeding of worms. If you can get enough bedding to start breaking down so that the microb food sources are abundant then expect sucess but if not then failure is garenteed. Worms needs are varied the same as any living organizems so keep that in mind as you try to farm your squirm.

The most perfact environment that composting worms need can only be acheived by keeping them in the dark, at around 70-75 deg F, in decaying organic material full of various microbs, that is moist and full of air with plenty of airflow and has a moisture level of 70-90 percent humidity.

It is possible to not have that sour smell but there are so many variables that can affect how well your bin is doing.

How many worms did you start with, how long has you bin been up and running? There may not be enough of a population yet to go through the amount of material in your bin.

The whole worm composting process works on bacteria. Generally, aerobic bacteria (type that use oxygen) decompose organic matter and produce less of the alcohols and sulphur compounds created by anaerobic bacteria (exist in the absence of oxygen) that cause those sour smells.

How much material is in the bin and how deep? There will be all types of bacteria around no matter what (they're everywhere). If there is partially composted material that is deep enough that it is getting little oxygen it is possible for enough anaerobic bacteria to be producing those sour smelling compounds even if the bin conditions are "OK".

Also, check how wet the material is. Saturated bedding material can prevent the exchange of O2 and CO2 creating pockets of favorable conditions for anaerobic bacteria to multiply. The system on a whole can be OK but have areas of anaerobic bacteria creating some of those sour smells. Moisture is important for worm health. Excess moisture can be OK for worms but not as favorable for people so it really is a balancing act to make it OK for you and still be OK for a worm bin.

No matter how well you maintain your bin, a freshly fed worm bin can have some off smells. I have a couple of rotten potatoes in my bin. I can't smell them unless I stir up the bedding, but they do smell. I also feed my worms onion skins. No matter what I do, onion skins are going to smell for a few days. The smell isn't strong, but it is there. Broccoli, cauliflower, etc., anything that has a strong smell will give off a smell for a few days when it is fed to the worms.

A lot may depend on how sensitive your nose is.

I read on line about a large worm farm in California that composted de-watered paper mill sludge. Its paste and the paper fibers that are not right for good paper. Too large, got bark on them and so forth. They made windrows of the sludge and introduced the worms. Didn't add any other food. The worms did just fine.

I would think that food scraps are not needed. We raised worms for our own fish bait for about 50 years and never used any thing but leaves green or brown did not seem to matter. I just found out in the last couple years about the kitchen scraps. Oh ya guess I knew about coffee grounds. That's an old one.Oh and we used a little garden soil in the bottom too. I had the best luck with green clover.

Curt :-)

That dirt smell, if you are referring to the normal smell of freshly turned dark soil, is made by actinomycetes. Not dirt itself. If actinomycetes aren't munching away in your bin yet then you won't get that smell. Most bins are too wet for that. Optimum conditions for actinomycetes are not the same as those for worms. Worm bags like the "Worm Inn" can allow for two different environments with plenty of airflow. I made one just to see how well it works. I was very impressed.

The way they work is you top feed your worms. Don't bury. Just cover a little. I used cardboard. The worms stay toward the top. They have no reason to hang out in the bottom like in a "Worm Factory" because water doesn't collect and the bag breathes, thereby keeping the castings at much lower moisture level than the worms prefer. Anyone with a worm factory can tell you that worms can always be found in the lower tiers, particularly if you don't allow aeration. Same with a plastic storage container bin. All that moisture is attractive to the worms, but not the actinomycetes. The extra aeration in the bag allows the actinomycetes to flourish. The castings from the worm bag I made were identical to fresh turned earth and I didn't have to harvest out worms. The downside is that they have to hang from something.

fosteem, the worm farm in California was (is? I don't know if they are still in business) composting cardboard sludge. It would have had a lot of glue in it.

Yeah, I don't know if that operation is still in business but there is a huge difference between the sludge they were feeding and plain cardboard. Don't get me wrong, I love corrugated box for bedding, but I wouldn't try to raise worms with only that. Throw in some coffee grounds and you would probably have some happy worms. Keep in mind that cardboard takes a long time to break down, and coffee grounds are fairly slow too. How about cardboard, coffee grounds and just a sprinkling of corn meal, huh?..The worms have to have some food(bacteria, protozoa, fungus) Without it they will starve, or at least get very thin and not reproduce. Steve

Thanks for all the great information.

Interestingly enough not long after I asked about the smell in this forum, I walked into the room where I keep this 55-gallon-flow-through bin, I noticed no smell other than very mild cardboard-like or dirt-like smell. Again the smell is very very mild. I think people walking into the room would not know I have earthworm bin. And I use t-shirt as a lid.

I think I could guess as to why the smell is gone.

1. The old bins had no drainage holes where as this new 55 gallon flow through bin has good air circulation with bottom hole and top t-shirt lid.

2. With the manure/leaves/coffee combination, I noticed my worms have been a lot more active recently, which probably adds even more aeration therefore better air-flow.

I started putting a little bit of food the last couple of days. And so far so good.

I think the key here is anerobic vs. aerobic instead of food vs no food IMHO. Actually, the health of the bin relies on how anerobic your bin is.

I am so glad I found this form. I read most of the articles, old and new and learned a lot.

If you just want to get rid of cardboard with composting, throwing them onto a CP-pile or composter will break down faster than in a worm-bin and in larger amounts too. I don't think there is a household with NO food scrap at all, whether it's veggie or fruit, just give it to the worms. If you have no worry about fruitfly eggs, freezing the scraps overnight just to break the molecule walls (? something anyway)to help decompose, then cover with several inches of
shredded cardboard and/or newspaper should limit the smell and you get happy worms. Happy worms will make lots of poop >>> and that will make YOU happy, LOL.
Seems like you are very concerned about smell; just make sure you don't put anything from the onion and cabbage family and I think you should be fine. Since you are so worried, I doubt you will overfeed them with organic matter so, just lighten up and don't get too stressed out because of a smell that might or might not be there.
Happy worming.

My husband doesn't like the smell, so I'm very careful with feeding. A good solution for me has been to cover every feeding with a sprinkling of dirt -- it's actually a 50/50 mix of dirt and coir. I just dust the feeding, then put a couple inches of paper on top. This takes the smell down to zero.