A ”soil factory” is something we came up with years ago to describe a place where you make soil using bokashi.
It can be a bucket, a tub, a bag, a planting box, a barrel, whatever you have on hand basically. The thing is that it’s used ONLY for making soil, not for growing things in.
But otherwise, it’s basically the same as any other bokashi process. Mix bokashi with poor soil and wait for the soil to become great again.
You can have a soil factory indoors or outdoors. Or both.
There are benefits to both, and they largely depend on what sort of climate you live in, and what type of gardening you’re doing. Also, which season it is.
You can make a soil factory pretty much in any way you want it. Strong or weak in terms of nutrients — this depends largely on how much bokashi and soil you have on hand, how much space you have, and what you are planning to use the end product for. But 50:50 bokashi and soil is a good mix to start with, you can develop the concept from there.
There are only two basic rules with a soil factory, whether it’s inside or outside. The mix should not become too wet, or too dry. And it needs to be able to breathe — in other words no lid.
The mix should however always be topped off with a layer of soil (of whatever quality), you shouldn’t be able to see the bokashi food scraps at all.
If you think about it, making a soil factory is very like making a hole in the ground and digging down your bokashi. You could say the same about preparing a pot plant tub or other container for planting in; it’s basically the same thing as a hole in the ground with bokashi and soil mixed in.
Let’s get a bit more specific here. Indoors first.
Find a nice warm spot
For a soil factory to work indoors you’re going to need a certain amount of heat, ideally room temperature. If you live in a cold climate (like I do) you’ll get this. Our cellars are normally pretty cold and while you can make a soil factory in a cold space it will take forever for the transformation to take place. Fine, though, if you just want to store your bokashi somewhere until the spring.
So 20+ degrees C is ideal. Above 15 degrees you’ll get a slow transformation, below that, nothing much will happen.
Some people have small soil factories in the bathroom, on a heated floor. This probably really annoys the family but it’s a great way to make soil — it can go as fast as two weeks.
You can also recreate this concept in a cellar by using a heated mat. I made one at home by taping weak electric cables on the underside of a big planting tray and placing that on top of a block of styrofoam. Not very fancy, and the styrofoam melted a bit, but it worked and you get the idea. (I also use it for starting up seedlings, so it’s quite a handy thing to have. )
An indoor soil factory needs to be a convenient size to move around if necessary, 10 to 20 liters is often good (bigger than this and you’ll need wheels).
Wider and lower containers are better than higher and narrower, makes it less likely you’ll spill soil and bokashi all over the floor, and easier to poke around and have a look how things are going.
While outdoor soil factories will need drainage, indoor soil factories need to not leak. So no drainage holes. But bokashi can be a bit wet, so you’ll need to think about this. If the mix in your soil factory is wet (probably because the soil itself was wet and unable to absorb moisture from the bokashi), then you will unfortunately have a problem with smell.
This is also part of the reason for using an open bucket/tub/container. It needs to breathe, much as soil breathes in nature. Usually any excess moisture just evaporates from the surface of the soil, but if it is soaking down to the bottom of the tub you may end up with a rancid layer that is less than pleasant.
The best way to counteract this is to start every soil factory with a layer of absorbent material.