Pure Castings vs. Vermicompost? What to ask your "Worm Guy"

J. James

In Bloom
There is so much BS in the worm game that purchasing quality products and learning about making your own castings can be quite confusing.

You'll see many advertisers using claims like:

"Pure Worm Castings"

"No manures or yard waste in the worm bedding and they are grain fed."

What I encourage you to do is ask some questions about how the worm castings are produced. Once you get a few questions answered I think you'll have a much better understanding of the quality of the product you are considering.

6 Questions to ask your worm guy:

1. What type of worms do you use?
2. What type of material are the worms fed?
3. How long are the worms left with the material to make the castings?
4. What type of "Worm Feed" are you using to supplement their diet?
5. How long have you been in the Worm Casting business?
6. How long has the ready to purchase product sat around?
7. Are they 100% Pure Castings? (Run if they say yes)

Red Flag Answers: If you get several of these red flag answers I would avoid using the product.

Question #1:
Canadian Nightcrawlers, African Nightcrawlers, European Nightcrawlers. Many times when you get this as the first answer you are dealing with a business that uses small black plastic buckets with Black Peat, worms and an indoor temperature controlled facility. None of which are great for the environment, and all of which end up with a low-quality casting material that looks like pure castings. Note: Many reputable worm farmers will use European Nightcrawlers and the type of worm used on its own doesn't mean much. I do find it strange that many of these dealers label their worms as "Canadian Nightcrawlers" which are in fact just Lumbricus Terrestris or normal European Nightcrawlers.

Question #2: If you hear peat moss or black peat, or "No Manure and no waste" then RUN the other way. Worms best use is to recycle waste materials and the best way to feed worms is with plant-based thermophilic compost which is often times a manure-based compost. This way you deal with a waste problem while creating a new product. If your worm farmer is shipping peat moss all over the world just to make castings then they are not doing it right and the peat moss isn't enough food so they will have to add "grains" or worm chow products.

Question #3: If you get a response with something like, "14 days" or "Not Long" or "A couple of weeks" then you should look elsewhere for your materials. Good vermicompost is typically made with a minimum of 45-60 day retention times and sometimes longer that way the worms can properly work the product.

Question #4: If the worm farmer says they feed with grains, this typically means a chicken mash type feed or a Purina Worm Chow type of feed. Worm farmers typically use this feed to fatten worms up for sale and also to supplement the Black Peat Moss they are feeding the worms. The black peat moss works great for the production because the lack of nutrients keeps the pile of peat from going thermal and killing the worms.... but it doesn't have any nutrition so the farmer is forced to use worm feed. Again, why we ever want to Purchase goods to feed worms when the whole idea is for the worms to process waste products and produce? When worms are fed plant-based materials from compost they are getting much more than nutrients. There are plant growth hormones and other benefits that are of primary importance when using finished vermicompost. Don't cheat yourself and use castings that were raised off of Peat and Grains, that might be fine to produce a fat worm for your fishing hook, but not for creating diverse finished vermicompost.

Question #5: If they just started the business a few months ago and have purchased a "Franchise" model for creating perfect pure castings every time.... you want to stay away! These new companies are purchasing a business model that is built off of the Peat Based, Plastic Bucket Housed, Grain fed worm systems. Anyways, not all new businesses should be avoided, but the ones using the same model from these major worm companies should be avoided because the end goal is to churn out a Pure Casting product every 2 weeks and feed them imported peat moss. That is not how castings should be made!

Question #6: If the worm farmer says.... well that is last years castings.... stay away! Storing Vermicompost can be done but you want to avoid the Pre-Bagged worm castings from your hydroponic store that has had the same inventory for 6 months left over from last season... This will be a waste of money. You can get a decent product that has sat around a few months as long as it was stored in bulk with good moisture content.

Question #7: If the worm farmer is basing his High Dollar Price off of the fact that they only sell 100% pure castings you should look the other way. Some of these businesses understand that it's a ridiculous claim to make so they end up playing it safe and saying 99% castings. Who decided it was 99%? Some microscope lab? How would you know if the Black Peat looks exactly the same as the castings? These companies are practically starving worms so they can re-ingest the same material over and over again to make an end product that is closer to pure castings. The problem is that most of these companies aren't "screening" out the pure castings. Instead, they are feeding with black peat that looks almost identical to worm castings before it's even fed to the worms. Might as well just by the peat moss and save some money.

J. James

In Bloom
(Excerpt from Vermiculture Technology page 292)

The intended end use of a vermicomposted waste helps to determine which of its characteristics may be important in assessing its quality, so it is important to list all of the potential quality criteria for vermicomposts and how they may be assessed. When specifying details of a vermicomposting operation, or evaluating vermicompost products, information about certain aspects of the vermicomposting process may be important. The vermicomposting system used (e.g., bin, windrow, wedge, continuous-flow reactor system, etc.) should be specified, as should the primary raw materials (feedstocks). Differences in process types and raw materials have been shown to have a very strong influence on the quality of the end product and its suitability for particular applications and value (Edwards and Arancon 2004). Any preprocessing, such as leaching or pre-composting, should also be described, since this may have considerable effects on qualities such as available nutrient content, contamination with viable weed seeds, or human pathogens. Any amendments with inorganic materials made during the vermicomposting process, such as application of fertilizers, lime, sulfur, and so on, should also be noted, since these may have effects on the final chemical characteristics of the vermicompost, as well as possibly affecting its certification as an “organic” material.

Other information essential for characterizing a vermicomposting operation includes an accurate assessment of the earthworm species used and the average population density in the system, the processing time (material throughput) for a particular batch, and the duration of storage of processed material or vermicomposts.

All of these can affect the quality, stability, and maturity of the resulting product. As already mentioned, the rate of material throughput per total weight of earthworms may be a very important criterion for classifying and registering vermicomposting operations and their resulting vermicomposts.

So how do these "Worm Castings" companies produce a "Pure Castings" product that looks like black coffee grounds?

Here is an inside look at a very popular worm casting production model.

Producers using this system may not know better and will claim it's the best, but common sense will tell you otherwise. When making anything from scratch, the best ingredients will make the best outcome. For making worm castings the worm farmer should only be recycling waste not buying new ingredients to use like peat moss, that is just a waste! Why harvest a peat bog just to make castings when the best vermicompost comes from worms fed thermophilic compost?

Here is a quote from a Worm Farmer named Patrick G. Perry. on Pure Castings:
"The goal is to create as many castings as possible using a process that carefully balances the worm's nutrition in an environment that is overcrowded and nutritionally deficient. This process can be utilized with any composting worm, but Ee's have several distinct advantages using this process. As a general rule, changing any of the parameters will result in disaster."

Here are their basic principles:

Worm ratio is 100 adult worms per gallon of bedding mix. ie.: 250/2 1/2 gal or 400/4 gal

1. Michigan black sedge peat processed by Michigan Peat Co. is used as bedding. Any other bedding that has nutrients will become too exothermic if substituted.

2. Feed (6oz feed/4gal bedding)is worm chow or chicken mash; it may be a combination of the two to reduce cost. Milk substitute or similar (calf milk replacer) may be added in small amounts. The blend and ratio of feed to bedding is critical: too much feed will cause the bedding to become too exothermic.

3. Moisture is the minimum that the worms can tolerate. (30%) If too much moisture is added, the bedding will become too exothermic.

4. Buckets are used and kept covered because the worms will escape under the conditions they are forced to live in and to prevent drying of the worms and bedding. They make excellent holding and manipulating containers.

5. The worms are separated and rebedded after 14 days because there is insufficient nutrients left in the remaining bedding/feed mix to support the worms. After passing through a 1/8" screen, because the vermicompost is consistent, it looks like vermicast.

6. Temperature control and sufficient ventilation is critical.

7. Castings, cocoons, and large worms are easily separated using 1/8" and 1/4" screens.

Here are the specifics on the above posts:

Michigan sedge peat is black in color, mucky and is formed from a variety of plant materials - reeds, sedges, grasses, and cattails mostly. It is more decomposed than Sphagnum peat. Therefore, it has a finer texture and lower air-filled pore space than Sphagnum peat. Its water-holding capacity is lower than that of Sphagnum peat. It is basically anaerobically decomposed plant material (muck) that has no nutritional value and is expeller processed by Michigan Peat Co. into grains that look like Ee castings.

Worms can get a little nutrition from regular peat moss because of their enzyme cellulase which digests the cellulose cells in the peat moss, similar to how they digest any plant's cells using the enzyme to convert cellulose to glucose. Sedge peat has no cellulose remaining to be digested and turned into sugars. Castings derived from sedge peat and worm chow will not have any more nutrients in the vermicast than what is introduced by the digested worm chow.

2. 6 ounces of worm feed is a starvation diet for 400 large African Nightcrawlers during a 2 week period. Feed becomes slightly exothermic as soon as it is mixed with the peat and moisture. Increasing feed amounts will create an exothermic environment that will kill the worms. Bedding with manure or any bedding with cellulose, 'brown' material or nutrients will do the same.


Extract Artist (BHO)
cpl years back i used to raise and sell composting worm EGGS just the cocoons, I kept the worms for my self and sold off excess castings as well!

This is fantastic information!!

I had 6 18 gallon bins i think at the height of my running.. Damn was it alot of worms alot of sifting and alot of work!

Now i just have a 33? Gallon bin and like 5k worms now churning thru my garbage boxes from amazon and whatever food crap i can find.

i also feed them azomite and mazuri worm chow but thats cause from my understanding it actually speeds up reproduction in the worms or some bullshit. I dunno it was cheap and i see a massive amount of baby worms now so im good with it :D
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