Wood chips themselves are too high a carbon source for most things to grow well in them. Also, the big particle size does not hold water real well. Additionally, some trees are allopathic, which may still be present on fresh wood chips. If I were you, I would try to find a nitrogen source (could be food scraps from restaurants) and then mix them with the wood chips and compost that mix. When the mix particles are fine enough to look like store-bough seedling mix (you can sift it), then it would be ready to start planting seedlings in. Because you may be getting your nitrogen from a variety of locations, I would check your batches of compost with one of those mini chemistry soil tests for the basic nutrients and pH, then add amenities accordingly. Basic soil tests do not list Calcium or Magnesium, though often times I believe (since they often mess with pH) you can tell based on the pH and content of the mix. If the pH is low and you didn't add a source of Calcium and Magnesium, you probably should. Common sources are egg shells, oyster shells, sea shells, dolomite, calcium carbonate, agricultural lime (different than builder's lime), milk, bones, and some plant accumulators if your soil is already rich in those nutrients. If your planting medium is plant-based from healthy plants, then you can assume most of the other micronutrients are there in sufficient quantities.
Now, you say composting is difficult there - why? Is it a totally in-door facility? If that's the case, perhaps you can vent the pile to the out-doors?
If that's not possible, perhaps vermiculture can help you out? I'm not a vermin person, but maybe you can collect recycled paper instead of wood chips, and then let the worms take care of it? Then you could have a worm and seedling business?
If the wood chips are fine enough, you could add some in to another mix in low enough quantities that it won't sap your seedlings of nitrogen, but for the 10-20%, I can imagine that being, that would then result in you having to add more fertigation to the seedlings for them to get large and beautiful, I can't imagine it paying off.
If you are in Denver, there must be some larger wholesale nurseries there. Call and ask if they have any used mix they want to get rid of. We have a local one that just gives the stuff away via ads on Craig's list. It's that or paying the dump.
Over the years I've gone and gotten several yards of it. It can be a mix of stuff (sand, peat, perlite, bark, fines... ) but it's all good stuff. There can be plant debris in it, so I have to sieve it through 1/2 inch hardware cloth, or just pull out the larger pieces. It's fast and easy. I have over 100 shrubs/trees in 15 gallon pots (also found on Craig's list) growing in it with no problem. If you are worried about any diseases for tender varieties, you can solarize it. Ive also gotten some interesting but damaged plants that were tossed out with their mix.
If you can get chips from tree trimmers, especially with leaves in it, just pile it (not so big as to invite spontaneous combustion) and in a year, sieve out the good stuff. Let time be your ally.
hau Gilbert, In the Denver area you can get good results from composting by using the tumbler method, it helps retain proper moisture levels in the bin and it also speeds up the decomposition so you get good compost in around 20 days instead of months of waiting.
The best additive I've used other than animal manures for additions to wood chips being composted is fresh grass clippings. These tend to be a good source of nitrogen.
Of course if you can source animal manures to add to them, then you are ahead of the N game composting wise.
I've made wonderful potting soil from woodchips with just one amendment besides moisture....urine! Just pour it on, or apply directly, turning all occasionally. If the pile begins to smell, wait a while before adding more. If you can keep it moist, and the chips are fairly fine, you should be able to have usable potting mix in a year or so......A bit of ash helps mineral content, and odors, as well.....
I've thought of trying to get stuff from a conventional nursery, but I was worried that the soil would be full of all kinds of undesirable chemicals, especially neonicitinoids. What do you think?
Ask them. I know the nursery where I get mine, and know they don't use really toxic stuff. In the beginning, I asked if I could eat produce grown in their mix. They said yes.
Since you will be wanting an on-going supply of mix, you probably need some fast, and then as the months pass you'll need more. While decomposing wood chips take time, you can start piling those up now for later use. And concurrently work on the potting mix for now as well. You don't have to have it all ready now, so maybe a small tumbler might work for when you need mix fast.
Since I've filled all my 15 gallon pots with free stuff, one thing I did learn is if it breaks down really fast, it will continue to break down in the pots and you could be left with 'punky' mix. I once obtained the best looking semi-rotted chips. I should have used them as compost because they just kept breaking down and eventually I had to repot what I had planted in it. That is not the norm however. (One of the reasons pine bark fines is common in mixes is because it does not break down as fast as many other things)
That said, some of the best 'mix' I ever had was decomposing chips from a mix of juniper, eucalyptus, and mulberry that had been trimmed and chipped from my own trees. That stuff lasted a good long time. It was great.
Many growers also use a percent of sand in their various mixes too. It drains well, and is not very expensive as a filler, but it can make the pots heavy if you use too much.
Gilbert, you can build a tumbler any size you want.
At my last nursery I built a tumbler with an 8 foot diameter, I used a plastic sheet for the actual tumbler cover, with some 4 inch angles bolted on the inside for additional mixing when turned. We used a gear drive system I found at an old soybean meal plant that was being sold off piece by piece.
You could even do this part with bicycle drive parts and an electric motor.
I always prefer to build instead of buy, but you can buy very large, commercial tumblers for composting, however it is much better in my thinking, to build your own, that way you can size it to your specific needs.
The largest I've ever seen is at our county government composting site, it is 12 foot diameter and 20 feet end to end with an electric motor running a chain drive to turn the tumbler. They fill it completely before they start it up, it is on a timer so it gets 4 turns each day.
For Nitrogen spent coffee grounds and urine are probably the two best ways to get plenty of N into your browns.
I use a 50/50 blend but if you are using SCG and Urine, you can use a 1/4 greens to 3/4 browns ratio with no issues at all.
On the farm most of our browns are used up animal bedding straw, this has urine and poop in it. To this I add a layer of clippings from the mower and SCG to get it all heating up.
I make sure the SCG are wetted once the layer is on. I use two methods for making hot compost one for the tumbler, and No Turn for our heaps.
The heaps are more complete, browns, greens, kitchen waste that doesn't go into hog food. These take about 6 months to finish, the tumbler takes 14 to 16 days and from it I get a cubic yard of finished compost every cycle.
Great advice Bryant! I really have to try a giant tumbler. I wonder, could I just roll it around the ground instead of mounting it in a frame and using some sort of gearing? Or pull or push it around with a tractor or truck? Maybe bolt angle irons to the outside as well and use it as a crimper/ roller on cover crops at the same time? Talk about dual purpose!
How did you fabricate and attach the ends? What kind of plastic sheet did you use?
I use wood to build giant tumblers, two sheets of plywood for each end along with 2x4 re-enforcements the body is 2x4's and the interior "paddles" are angle iron.
I don't use treated lumber so you have to be ready to replace it with a new one after about five years of steady use, the 2x4 body is able to let excess water leak out to the ground.
I don't see any reason that would prevent you from using it on the ground, except for emptying the finished compost, but that would just be a little more inconvenient since the opening would be at ground level. Might even work better than the ones I've built for dumping into wheelbarrows.