For the past year I have been piling up branches and limbs on a border of the yard and now it is about six feet high. I had wanted to experiment with a hugelkultur but the limbs are not very large and include twigs as well as grapevine cuttings, dead sunflower stems etc. My question is whether I can compost all of this with minimal effort or whether I should do something else with this as the winter comes. I also wonder if I add organic materials and scraps as I do with my compost whether the rats and other critters will bed down in there and cause me trouble later.
My personal experience is a bit different than what @Bamboo indicates, but I'm not trying to get there by adding kitchen scraps, either.
Once upon a time I rented a chipper - it was an overall miserable experience since dis-assembling a pile that was not stacked specifically with chipping in mind is a slow, tedious process, and chippers can be fussy (the one I got liked to jam on grapevines, which many of the branches had entwined, for instance) as well as noisy and dangerous.
I have found that pulling a truckload of horse manure up the pile of brush and shoveling it on top makes a very significant contribution to the speed of breakdown - not only does it add nitrogen, it also helps to maintain moist conditions that favor breakdown/rot of the wood in the way that an open, airy pile does not. If it's a big pile or a small truck, use 2 or 3 loads. Revisit it in a year or two. If you can get and can stand to shovel chicken manure it may work even better. Horse manure is easier to come by and more pleasant to handle, for me.
I don't see anything against a "hugelkulture of smaller twigs" if you'd rather do that. Or, plant tomatoes/squash on the paragraph above and you've kinda got that - both plants are typical "happily growing in the compost pile" plants, so being planted in pure manure won't bother them a bit, particularly if it's been aging all winter (pile now, plant in spring.)
To compost a brush pile in-place you have three problems:
- Lack of nitrogen.
- Lack of water.
- Lack of surface area.
One way to solve #1 is to gather lawn clippings or other green matter (leaves, etc) and add them to the brush pile. This will help with #2 as the clippings have water in them, and will act as a sponge to collect and hold rain water. #3 - without chipping the wood you're kind of stuck with what you've got. If you've got a tractor that has a front-end loader on it you could use the loader to crush the pile and break up the wood in it a bit. Anything will help, but not much besides chipping will help much.
Be patient - it's going to take quite a while to compost down an unchipped 6' tall brush pile. I suspect that "quite a while" means "multiple years". Best of luck.
If you have what is basically an untidy woodpile, it will eventually decompose not by composting but by rotting. However unless you have a very "rot-friendly" climate that may take 20 years or more, and in any case the end product will most likely be full of organisms, like honey fungus or so-called "dry rot", that you don't want to spread around the rest of your garden (or invade the wood used in building your house) unless you want all your other plants to decompose faster than the woodpile did!
Find a way to convert it into chipping-sized pieces and either compost them over time mixed with "green" material, or just spread them on any bare ground for weed-control. Or (the simplest option) just get somebody to take the stuff away. If you have substantial sized pieces of timber, somebody with a wood-burning stove may be happy to take them away for free.
With the benefit of hindsight, next time keep the more compostable ingredients (leaves, plant stalks, etc) separate from the "wood."
Incidentally, if you rent a chipper, also rent a chainsaw. That will make "dis-assembling a pile that was not stacked specifically with chipping in mind" a much quicker process - and if you accidentally try sawing into a few rocks, it's not your chainsaw that you are damaging!
If its lots of woody stuff, it'll take years to compost down, regardless of any 'greener' additions you may make to the pile to supply nitrogen. Adding kitchen scraps may well increase the risk of unwelcome creatures in the pile as it stands too.
If you're not going to use it for hugelkultur, and you want to turn it into useable compost relatively sooner, the best thing to do is chip all the wood by running it through a wood chipper, then build a compost pile, ensuring that you don't add too much so the C:N ratio is kept within bounds. Woody materials count as 'browns' or carbon, so you need to balance that with 'greens', or nitrogen to create a C:N of 25 to 30 parts carbon to one part nitrogen, see link below for more detail
UPDATE: If you can't borrow or hire a chipping machine, the other option is to burn the pile, if you're allowed to where you are. Some of the resulting ash can added to a compost bin or heap.
Branches and twigs are terrible for the compost bin. I put them in when I was new to composting and not only does it take a long time to break down but it also gets in the way of turning the pile. I would not recommend using branches and twigs in your compost bin unless you can shred those into very small pieces. I generally just put those in my green bin for the waste management company to recycle