We do most of our own butchering, so periodically we end up with a lot of bones.  Bones take a long time to break down in compost but they contain a lot of useful minerals.  So the questions is: would it be better to make bone char or will we lose to much of the benefits?  Any one have experience with the benefits and disadvantages with bone char?

Check out Salatin's compost operation.

They do a several step process with wood chips and get a really finished compost with the bones in there. I don't have the pole barn setup he has to do this in, but I'm doing something sort of similar with wood chip piles, just bury the bones and let it sit and cook. It takes Polyface close to a year for finished compost and for mine maybe two, but I don't wait for finished compost. I guess the upshot is that it doesn't take as long as you would think to compost bones as long as the temperature is high. If they are cooked bones you need to keep dogs out of it.

With bone char you get to keep all the Ca and P and have the added benefit that animals won't dig for them as they loose all their odor during the charring process.  Nothing like doing a planting with bone meal added to the soil, then coming back the next day and seeing your plants excavated out and laying on the ground because a critter was desperately looking for the bones.  I've never had that happen with bone char.  When I've charred whole bones I've also noticed that they become much easier to break after....I assume due to the loss of connective proteins that run through the bones.  Unlike raw bones, bone char also brings the beneficial binding properties of biochar due to it's structured carbon.

Instead of burning the bones into char just roast them at 400 degrees f for around 3 - 4 hours, this changes the molecular structure just enough for all the minerals to be easier for bacteria to process.
If you do the roasting then make a way to pulverize the roasted bones, you make it even easier for the microbiome to process and free up the minerals in the bones.

Redhawk

edit: pulverizing also lets you cover more space.

it's not compost, but here's another idea for making good use of old bones:

Sepp Holzer's Bone Sauce

I haven't tried it, but it seems to be a wonderful (re)discovery!

As I understand it, many plants can only absorb chelated calcium. (Calcium that has been bound with amino acids or proteins.) So I think your calcium needs to go through bacteria or fungi regardless of your method. So I don't think that a high degree of processing like making bone char is really needed. Bone char is OK too, it might just not be worth the effort if you don't specifically need bone char distillates or the bone char itself for some specific purpose.

Like Bryan was saying, You just need to cook the protein or fat off. The bones themselves don't need further processing to be useful. It might easier to just use a basic recipe for bone stock(broth). Make bone stock by simmering(just below a boil) the bones with a bit of vinegar for 8-12 hours in a stock pot or crock pot. You just need enough cooking to get all the fat and protein off the bones. The vinegar helps break up the collagen(boiling collagen with an acid makes gelatin) and helps demineralize the bones.  If you don't need much broth(or you have a lot of bones) you can feed the broth to pigs, chickens, or pets mixed with their food. The bones still retain most of their minerals, but they start to get crumbly. I make bone stock a lot, and the resulting bones really don't have much smell once they have dried off.

Once you have gotten the meat and fat off the bones, just break/grind them as coarse or as fine as you want. If you don't have an immediate need for calcium in the soil, there should be nothing really wrong with just using coarse chips. They would be broken down in the dirt directly instead of in the compost pile.

I use soldier flies to process bones. After being cleaned by soldier flies, other animals show no interest in them. Probably no use to the OP unless they have a heated greenhouse or something similar, but it works really well. You can even use whole animals.

In Korean Natural Farming, charred bones soaked in vinegar to get water soluble calcium-phosphate. The strained solution after 7 days, diluted 1:1000 and used as a foliar spray during vegetative growth, flowering and fruit ripening stages.

Remaining charred bones pulverized and used in soil or worm farms.

Just did turkey broth in a pressure cooker.
The leftover bones disintegrated in my blender and I poured the results out for the chooks to scratch into the soil.
That said,  bone char is awesome to the point that I daydream of turning barrels of KFC waste into terra preta for container growing.

We heat with a wood stove and use the ash in the garden and in the chicken area for dust bathing.  Would bones added to the wood stove have the same effect for bone char or would it destroy them too much? Sorry, bone char is new to me, but I'm trying to improve with making full use of every part of our chickens.

Tina Hillel wrote:We heat with a wood stove and use the ash in the garden and in the chicken area for dust bathing.  Would bones added to the wood stove have the same effect for bone char or would it destroy them too much? Sorry, bone char is new to me, but I'm trying to improve with making full use of every part of our chickens.

Because of the available oxygen in the woodstove the carbon in the bones is burned away leaving white bones that are easy to crumble and have no odor.  They then make nice reserve pools of Ca and P in the soil when added.  Good question...I've done that many times and it totally slipped my mind (like sooo many things do....uggh!).


I also really like the suggestions of making bone broth first.  Gelatin is probably the richest source of the amino acid glycine.  Some studies have suggested that glycine plays a key role in the aging process as our body makes is able to make glycine, but as we age an epigenetically driven process slows down our ability to manufacture this critical amino acid.  After reading one of those studies I've added bone broth almost daily to my diet and my finger and toe nails have lost any brittleness that they were starting to get.  I'm in my 40s and little things like that have started to creep in.  I need to live near you Tim so I can help you out when you have too many bones on your hands!

Wow there are lots of great suggestions here, but I'll just add that the size of the bones can be an issue, so having a variety of options is worthwhile.

Tim doesn't mention what exactly he's processing but I know that my kitchen pressure cooker will hold any bones my chickens produce, but struggles with some of the largest Muscovy or Goose bones. I've got a canning pressure cooker, but no good place to use it so I have to have a really good reason to go that route. Maybe someone who knows more than me can comment on what breathing gear is necessary if one starts sawing up bones with power tools? I do believe there are some health risks, so please play safe.

I have planted some carcasses in the middle of at least warm compost and if the presence of fresh food isn't enough to heat things up, I've occasionally had raccoon visit long after I would have thought the worms/bugs/microbes should have taken care of things. Rural raccoon target rats as a food source, so I try not to do anything that will turn a coon into a pest that has to be removed. Making sure compost and carcasses are treated appropriately works for me.

I mentioned the 400 degree oven for 3-4 hours to my sister and her immediate response was, "too expensive". That suggests it might only work for people with cheap electricity, or a different source of energy for their stove. Do those experimental rocket ovens get that high?

I regularly add bones to our Pacific Energy wood stove - or at least the family pyromaniac does. I figure that we're getting a little warmth out of them after I've already made the bone broth from them and then they help to lighten the compost after that.

All that aside, bones aren't the only problem that needs dealing with if one needs to process larger numbers of small animals or 1-2 large ones in a short period. I have one farm acquaintance who deals with the guts + heads from a day of duck processing by fermenting them in home-made bokashi.  She's done this for years specifically because her farm location attracts many rats, mink and raccoon. There's likely info somewhere on permies that would give people the methodology, but she's doing this on a fairly large scale (think large garbage can) that would hold some of those larger bones or skulls that are more difficult to deal with. She's told me that once the bokashi process has worked on the guts/heads, she can add it to her compost piles without attracting unwanted attention or generating disagreeable odours.

You can make a big pile of altering layers of high-calorie wood (such as oak) and bones, and fire it up! It will get well over 400 Celsius. Just to be on the safe side add some additional wood. In the end you will have quite a bit off wood-bone ash and some bits of clean bones. By experience, producing pure bone black (bone char) requires a bit of investment to make it properly. I found out that it is quite smelly even for small quantities. It is definitely not an urban-friendly process.
Another thought is; you can get a rigid steel mesh-cube welded, drop the bones in, and let the nature clean those for you. Mesh size will need to be small, for dogs and such not to pull bones out; and something strong to be bear-proof. It is possible to spread some diseases by non-heat treated bones though, so do not include skulls or spine.
I never had luck with composting them. If it counts as composting, each of my dogs do process half a kilo of bones a week though. It does not end up in the vegetable garden but the remaining property gets the benefits by means of dog poo.
Edited: By bones I mean sheep or cattle bones not chiken's