I used to let the power company dump their chips at my place. Sometimes would get a hundred loads a year. I had so much chips I used it as a mulch to control weeds. I woupld pile it high as my tractor would lift and turn it every couple of months. It will break down pretty fast without adding anything to it, of course the chips I was getting where green and full of leaves. One will be supprised how little material that big pile of chips will produce once composted. I think the ratio is around one load of compost for every ten loads of chips and if you want to break it down to humis it is another 1 to 10. I never used my chips the first year as they had to much of the tannin acids and that would stun the growth. By the second year I used it strickly as a mulch around my garden crops. I would fill between the rows completely. I found this held moisture for the plants and suppressed weeds very well. At the end of growing season, I would then spread horse litter and till the mulch under and by next planting season, it would pretty much be gone. I turned a graden spot that was all fill dirt from a 90foot road construction cut site into dark fertile garden soil in about 3 years doing this.