January 2, 2014
I first learned about this technique from reading Sepp Holzer's Permaculture: A Practical Guide to Small-Scale, Integrative Farming and Gardening.
This is an invaluable resource for people working with Permaculture in cold climates.
In recent years, Paul Wheaton (the official, unequivocal Duke of Permaculture) has done a lot to promote this technique (as well as Permaculture and Sepp's work in general) and even made a video recording of Sepp Holzer presenting and demonstrating how to make Bone Sauce.
You can find more information on it at the Permies.com Forum and in the video below.
I will give a brief description of what Bone Sauce is, and how we figured to make it at Windward.
From what I can tell, bone tar is an extract from the charring of bones. Cooking them at a high temperature without any oxygen. It is the fatty components of the bone being melted/reduced out.
Freshly squeezed bone sauce.
This brownish black substance is very strong smelling, and can be diluted with animal fat before applying it to trees, shrubs and bushes that one wishes to protect from browsing.
The idea is that, the bone sauce is nasty smelling/tasting to herbivores. It literally smells like a mixture of dead animal and barbecue. It gives the herbivores the impression that what resembles a tree, is actually a decaying animal, and they choose to stay clear of it.
Some junk pots I used for the project.
To make the bone sauce, I first found two old pots that have a similar sized mouth. One pot is laid on another, with the bones in the top, and the bottom being used to catch the bone juice.
The bottom pot is buried in the ground,and the top pot is fitted with some kind of screen to keep the bones in when you turn it upside down. You can see this in more detail in the image above.
Split pine places around the pots, ready to be lit.
The two pots are stacked and a coating of clay around the seal of the two pots to help ensure no air gets inside. It is important the the air not ge into the reaction, because the volatile oils will tend to burn off.
Sheep fat and bone tar melting on the wood stove.
A bit of water can be added to the bottom pot before it is sealed. The water helps to dissolve the nasty smelling stuff. I found that this is not too important, as most of our bones have been used to make bone broth, and are already pretty well saturated with water.
A fire is the lit around the pots, and allowed to burn to coals. Sepp Holzer suggests to bury coals with clay to help seal in the heat over night. I have not found this to be all that important. We get a complete burn of the bones (ie they are all black) without needing to do this.
To complete the Sauce, I added melted sheep fat to the pure bone extract. Helping to extend it, and using a resource we have in quite abundance.
We have many gallons on bones left over from butchering animals, and making bone broth. In the past, we've just made bone meal from them, and used scattered in our many growing areas. But I think that this method gives us a greater amount of value for the bones, and still leaves us with a good calcium and magnesium rich fertilizer.
Bone Char. The left over bones from the process.
Turns out that the top pot I used was not very durable, and ended up burning out after 4 rounds of bone sauce. This is fine, since it was a broken pot to begin with. But i suggest getting a thicker pot. Preferably a set of large cast iron ones.
after 4 burns, the top pot was destroyed.
Applying the bone sauce is just like painting. Brush 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 under 4 feet in height as well as the main trunk all the way to the ground (to discourage rodent nibbles).
applying the bone tar
And there it is, a traditional and rather simple way to deter those pesky deer.