Questions and Answers:

Q: How accurate is the calculator? Will I see identical growth rates in my bin?

A: Umm... don't use the results you get from the calculator for anything incredibly important.



The V&R and D&E studies were done under carefully controlled environments. Yes, the results are obtainable. No, you probably won't get the same production levels in a typical bin. The best you can usually do is to mirror as many of the "lab conditions" as possible - ~80% humidity, temps of ~25C, a quality food source, and do your best to keep overpopulation from inhibiting your growth too early on. In a typical "worm bin", you'll have other challenges to overcome too - avoiding aneorobic conditions, trying to keep the moisture level consistent (almost impossible - an area of your bin will probably always be either too wet or too dry), etc.



On top of all that, the calculator's imperfect. Even if there aren't any remaining bugs in the basic math, it makes some assumptions. For example, it assumes that your Original Adult Worms all matured on "Day 0" and then determines their weight based on the age where that took place (dicated by the setting for # of days for a wormling to reach adult) - this will usually make those original worms "lighter" than an actual random sample of mature worms (though they will increase in weight as days go by in the calculator). In fact, weights are extrapoloated from 1 specific study, so don't put too much weight into the weight regardless. The graph can also be +/- 1 day when it comes to figuring out when a cacoon hatches, wormling becomes adult, etc.



The calculator never slows down the growth rate either (whereas in reality, reproduction will decrease as population density increases). You'll get exponential growth in the calculator as time goes on, to the point where you're got millions/billions/trillions rather quickly whereas in reality your worms will usually have overpopulated their environment and slowed reproduction well before they hit those numbers.



Short version: Use the calculator as a simulator for "what might be possible", but don't expect that reality will necessarily match the simulation.

Q: Can I use the simulator for other types of worms besides red wigglers?

If you manually input the appropriate values in the "Advanced Settings", sure (presets are all for red wigglers).



Note that weights will not be correct - the values for red wigglers are hardcoded into the calculator, so don't enable "show weight" if using another type of worm. Obviously you'll have to make sure your temperatures, humidity, food source, environment, etc are all appropriate for the type of worm you're simulating.

Q: How do I determine when my growth rate will actually slow down in my bin?

A: You'll want to start by determining your bins square footage. For simplicity, let's assume a 0.9 x 1.2 foot bin (around 1 square foot).



Next we want to figure out when growth will slow down. Here are some stocking densities from Manual of On-Farm Vermicomposting and Vermiculture (Glenn Munroe):

0.5 pounds per square foot (2.5kg/m2) : considered minimum stocking level

: considered minimum stocking level 1 pound per square foot (5kg/m2) : low end of common stocking density - slower reproductive urge

: low end of common stocking density - slower reproductive urge 2 pounds per square foot (10kg/m2) : high end of common stocking density

: high end of common stocking density 4 pounds per square foot (20kg/m2): possible to get density this high

1000 worms

In reality, the true number will probably lay somewhere in between.

Find the square footage of your bin. Use 1 pound per square foot model to determine at what worm-weight reproduction will slow. So if your bin is 1 ft2, then it should slow at 1 pound. 2 ft2 at 2 lbs, 5 ft2 at 5 lbs, etc. Plug your starting worms into the calculator. Select "Show Weight". Scrub the timeline until you reach the worm-weight from #2.

Using our small bin example, (1 square foot), growth will slow once we reach 1 lb/ft2.Use this as a "rough rule of thumb" - it's not exact, and depends on the weights/ages of the worms. 1000 worms that are all a year old and grew up in perfect conditions might be a lot more than 1 pound. On the other hand, 1000 baby worms will weigh considerably less.In our small bin, growth will really slow down once we hit about 1000 worms if we use the "rough rule of thumb". On the other hand, if we use the calculator's weight (by enabling "show weight), we might hit a pound once we have around 500 adults and 1500 wormlings (or some other combination depending on our starting values).Coming up with values for other sized bins follows the same process. Basically:In reality, worms probably don't have a sudden population density "cliff" where reproduction suddenly drops off (it's likely more gradual). Unfortuantely I don't have a way to quantify that right now - if at some point I come across enough data for me to slap together a rough density-vs-rate-of-decline formula, I may add it to the calculator.