The horse bedding likely has pee and poop in it which are greens. If it's wood shaving based, that's a super-brown. Depending on how much of each, and how old it is, it may be more green or more brown.

Best way to make compost is 'observe and adjust'. Try equal amounts of horse bedding stuff and kitchen scraps. Mix well and see what it does in 24-48 hrs. If it's stinky, you need more browns. Add some shredded newspaper. If it doesn't do much, but doesn't smell bad, that's OK as a tumbler usually won't heat up, even with 16 gal worth of fresh material. It might though, especially if it's too heavy on the greens.

Eggshells are essentially limestone and do not break down much at all. If you want to keep composting them, crush them in your hand before adding to the kitchen bucket. When the inner membrane breaks down it leaves smaller chips that are not as noticeable.

Mostly your problem is that you're using a tumbler, because they are hard to regulate, and usually not big enough to heat up so even a mix rich in nitrogen will not show you that it is by steaming a bit. Even the hot composting is cold, if that makes any sense.

If you have a place to empty the tumbler, say a small circle of fencing or chicken wire, you can empty it there to 'cure' for a couple months and start over in the tumbler. The thing about a compost pile or bin is, once you get one, you want a second one for best results. :-D

Thanks for the input. I should have mentioned that the horse bedding is a bag I bought to use as brown to start composting last summer before the leaves fell.

i live in a city with a fairly small lot that is mostly landscaped. No room for anything but a tumbler. Hope I can get it going better this year.

Is your bagged horse bedding compressed pine sawdust? That's my preference for a fast-acting dose of browns if the material going into a tumbler is too nitrogenous. Do I always get the initial dosage right? It hasn't happened yet. If the pellets break down but the contents still smell like a swamp, add more pellets. If the pellets do not break down and the material is dry, I'll know I've added too much sawdust, so I compensate with fish emulsion. Maybe after a few decades of this trial and error I'll finally have enough experience to get it right the first time.

As toxcrusadr pointed out, the progress inside a tumbler can be difficult to monitor. The material you see when you open the hatch is often the most highly composted material in the batch, but it can conceal other material that is nowhere close to being ready to use. Nitrogen-rich material can stick to the sides of the tumbler as sizable clods. Since the thick layer between the surface of the clod and the container never receives any oxygen, the pile is not making progress. If this is the case, empty the contents onto a tarp. If you've scraped out putrid clods from the sides, this is a good time to work them over with your sawdust pellets.

If it's too wet, you can also leave the door open in DRY weather and let some moisture evaporate (and more oxygen gets in too). A compost pile should be damp like a wrung-out sponge, not drippy.

Thanks guys! I will give it a try. What I had are the pine pellets. I'll give it a try with that and some shredded newsprint and see what happens.

And save more leaves in the fall!