By far the most time consuming part of pallet grow boxes is the filling process. It takes a heck of a lot of biomass to fill one. A box holds one cubic yard of material, which will translate into 27-30 trashcanfuls when tromped down and decomposing.
As I work around the farm, I always save whatever biomass I gather, be it clearing leaves and twigs out of a spot, pulling weeds, or removing an old crop. I store this debris in recycled plastic bags, or feed bags, leaky trashcans, whatever. Sometimes I'll just pile it up, like in the case of the coarse ferns that I'm removing.
I'm not too fussy in what I use. Hacked stems from ginger, coarse ferns, tree leaves, weeds. The only things I avoid are those that I've found to be aggressive spreaders and difficult to kill -- honohono grass, Mexican elderberry, and Bermuda grass. Most everything else dies during the decomposing period.
I don't bother to chop the stuff up. I leave it coarse......except for the fresh grass clippings (which by their very nature are finely chopped) that I add for nitrogen. I'll even use chunks of banana trunks. They eventually decompose just fine.
All the stuff in these photos went into the new box. I layered the various ingredients, adding 1"-2" fresh grass clippings or a little horse manure every foot or so for a nitrogen boast due to high amount of carbonous material I'm using, plus a shovelful of either garden soil or compost atop the grass or manure layer. (If the weeds I used had been pulled up with their roots and a bit of soil with them, I can skip this last step.) Since all the material was already wet due to the rain, I didn't need to wet the layers as I added them. If this were a dry spell, then I would wet down the layers. I'd fill the box a few feet deep then climb inside and tromp it down real good. I find that the sides and the corners often need extra fill.
Today I packed the box full to the top. Packed it down as good as I could. Next I watered it with a bit of extra water (a 5 gallon bucket).
Once a week or so I will go back and tromp the material down again. I'll also check to see if it's getting warm deep down inside. The goal is to not let the pile dry out if it gets real hot because the decomposition process will stop. To combat that problem I will add water as needed. And I'll cover the top of the pile with either an old tarp or some sheets of cardboard that I have wetted down. That helps keep the moisture in.
Now for the next few weeks there will be a cycle.....
.....tromp down the pile, top off the box with more biomass, water as needed.
Exactly what I put into these pallet boxes is highly viable. It all depends upon what's around. Lots of outdoor biomass from the farm. Kitchen waste. Livestock manure (not pig, dog, or cat, which is reserved for the hot compost piles.) Slaughter waste. Roadkill. Foraged waste fruits. Coffee grounds. By far the majority of the material is weeds, plant trimmings, grass clippings, and tree leaves.
Yes, it's like a hot compost pile. It differs from my hot compost piles in that the hot compost :
1- processes the pig, dog, and cat manures
2- gets urine inoculated biochar added to the layers
3- is temperature monitored
4- is turned in order to maintain high composting temperature for a total of 30 days
The pallet box material is never turned. It is layered as it is filled. At the end of a long season crop, or after two consecutive short season crops, the box is then opened and emptied. Then we start all over again.