Bone Sauce: A Tool for Deterring Browsing
Applying the bone sauce
Bone sauce is a product of the destructive distillation of bones — a process which separates the volatile organic components (aka bone sauce, or Dippel’s oil) from the inorganic components (aka bone char — mostly calcium, carbon and phosphorous compounds).
Bone sauce has a potent smell, somewhere between wood-creosote and rancid meat. When applied to the bole, branches, and shoots of dormant woody perennials it deters browsing by a range of herbivores. From wild animals like deer, elk and moose, to domestic stock such as sheep and cattle.
Keep in mind that bone sauce is proven to be effective with herbivore’s and not with generalists/omnivores such as a pigs or rodents.
For those working on a large scale, bone sauce is a fast, natural and highly economical way of protecting trees from browsing when compared with individual tree protection tubes or fencing.
When used in combination with thick rough woody-mulches to deter from physically getting close to trees, we have found bone sauce to be almost 100% effective in keeping herbivores off woody perennials. This is particularly true when there is plenty of other herbaceous understory plants for them to eat.
We have utilized bone sauce on a range of plants including Malus, Prunus, Morus, and Sambucus genus trees, walnuts and chestnuts, honey and black locust, willow, sea buckthorns, currants, raspberries and and other berry-producing shrubs.
We have seen no evidence that species, genus, or family has any effect on the success of the bone sauce. Additionally, we have been able to dilute it 50/50 with sheep or goat tallow before applying with no loss of effectiveness.
Freshly squeezed bone sauce
Making the bone sauce
As was said above, bone sauce is a product of the “destructive distillation” of bones. That involves heating up the bones in the absence of oxygen to temperatures around 600-700°C, until most of the organic material has been “cracked” or melted out, leaving a black “bone char”.
I originally came upon this method of making bone sauce from Sepp Holzer’s Permaculture: A Practical Guide to Small-Scale, Integrative Farming and Gardening. Here I offer a process that evolved out of my experience making bone sauce from Sepp’s method, with materials commonly available on a modern farm.
- 2 large capacity, heat resistant vessels of about the same size (cast iron or ceramic pots work well)
- metal mesh (chicken wire works well)
- a quantity of bones
- a shovel
- a few arm-loads of dry fuel wood
Some junk pots I have used for bone Sauce. (Notice the whiteness of the bones — that is
bone-ash, a result of oxygen getting into the mix because the pot melted during the burn)
First, bury one of the vessels in the ground, to the lip. Pack the second vessel with bones and fit the metal mesh onto it.
Flip the second vessel over, on top of the buried one, so that the bones are sitting securely on the screen.
When the pots are situated, shovel and pack earth around the seam between the two pots to help ensure no air gets inside. It is important that air is excluded from the bone chamber because the volatile oils will tend to form gases which escape the reaction — thus, you get a lot less bone sauce and of a lot poorer quality.
Place the firewood around the pots. I have found the configuration shown below to be effective.
Split pine places around the pots, ready to be lit
A bit of water can be added to the bottom pot before it is sealed. The water helps to more effectively dissolve the volatile components, ultimately yielding more bone sauce. We’ve found that the addition of water has not been necessary in our case because we make bone broth with all our bones before they exit the kitchen, and are thus already well saturated with water.
Sheep fat and bone tar melting
on the wood stove.
Next, a fire is the lit around the pots, and allowed to burn to coals.
Sepp recommends burying the top pot with the coals after the fire goes out, and coming back the next day after the coals have cooled. We’ve had greater yields and more consistent results not burying the top pot with the coals, and instead doing a second burn after the first is finished. Both methods are worth exploring to see how your results vary.
You can dilute the resulting bone sauce 50/50 with animal fat (goat, sheep, cow and pig would work well) or leave it full strength. We have had no loss of effect by diluting it. Since we render all our sheep, goat and hog fat it is economical for us to use some of the less desirable fat for value-added resources such as bone sauce.
Applying the bone sauce
You can apply the bone sauce with a brush, or, if you are feeling brave, you can put on some gloves and apply it directly with your hands. Be aware that the smell lingers….
Important Note: Bone Sauce should be applied in the dormant season, before there is any evidence of bud-swelling and sap flow.
The left over bones from the process
If the bone sauce is applied too late into the winter, it can “burn” the forming leaf and flower buds, and cause them to either die, become deformed, or not emerge at all. Bone Sauce will also burn leaves, flowers and fruit so be prepared for winter application.
We have not had ill-effects when applied during the periods of full dormancy.
Applying the bone sauce
Apply it on all the areas of the tree that a deer (or whatever you are trying to discourage) can reach. We applied to all the branches we can reach from the ground, as well as the main trunk all the way to the ground.
The bone sauce needs to be applied anywhere the animals you are trying to deter could get their mouth on the plant, so that no matter where they put their mouth/nose, they encounter the sauce.
Beyond bone sauce
I believe that this treatment of bones yields a greater amount of value than merely grinding the bones as a soil amendment. As you have both the bone sauce as an animal browse deterrent, as well as bone char which is just as effective as a long term calcium and phosphorous soil amendment.
The bone char is also significantly easier to break up with simple tools like the top of a mattock handle or a sledge hammer. It is akin to the difference between breaking up wood and charcoal.
We’ve taken to pulverizing the bone char and mixing it in equal parts with sawdust from the sawmill and ground biochar from gasifiers and campfires. We then put it in a five gallon bucket and urinate on it for several weeks.
A mattock handle and bucket are simple and effective pulverizing tools
The mixture is then commonly incorporated into our vermicompost system and comes out the other end as a very nutrient dense, biologically active soil amendment which we feed back into our growing systems.
Bone char can also be used as a filtration medium similar to charcoal, and as a pigment for paints and plasters. The char can also be burned in the presence of oxygen to produce bone ash, which has similar use as a pigment and ceramic coating. There are many potential uses and probably still more to discover!