Bone char

Bone char, also known as bone black or animal charcoal, is a granular material produced by charring animal bones: the bones are heated to high temperatures (in the range of 400 to 500 °C) in an oxygen-depleted atmosphere to control the quality of the product as related to its adsorption capacity for applications such as defluoridation of water and removal of heavy metals from aqueous solutions.The quality of the bone char can be easily determined by its color. Black charcoals are usually undercharred bones that still contain organic impurities which may impart undesired odor and color to treated waters. White bone chars are overcharred bones that present low fluoride removal capacity. Grey-brownish bone char are the best quality chars for adsorption applications. The quality of the bone chars is usually controlled by the amount of oxygen present in the charring atmosphere. It consists mainly of calcium phosphate and a small amount of carbon. Bone chars usually have lower surface area than activated carbons, but presents high adsorptive capacities for copper, zinc, and cadmium

Uses

Bone char is used to remove fluoride from water and to filter aquarium water.

It is often used in the sugar refining industry for decolorizing (a process patented by Louis Constant in 1812). This is a concern for vegans and vegetarians, since about a quarter of the sugar in the US is processed using bone char as a filter (about half of all sugar from sugar cane is processed with bone char, the rest with activated carbon). As bone char does not get into the sugar, sugar processed this way is considered parve/Kosher. Sugar processed in Australia does not use bone char. In Canada, Rogers and Lactania sugar is producted using bone char; the only vegan sugar is Redpath.

It is used to refine crude oil in the production of petroleum jelly.

Bone char is also used as a black pigment. It is sometimes used for artistic painting because it is the deepest available black, though charcoal black is often satisfactory and is more often used. Ivory black is an artists' pigment formerly made by grinding charred ivory in oil. Today it is considered a synonym for bone char. Ivory is no longer used because of the expense, and because animals that are natural sources of ivory are subject to international control as endangered species.

Historical production in the USA

During the settlement of the American mid-West in the late 19th Century a large number of buffalo bones, artifacts of an earlier extinction campaign, were a nuisance to the new inhabitants. One way to dispose of them was to sell them for industrial use for around $10 per ton. The payment to bone pickers was often for goods or services rather than cash.

By the end of the 1890's there were fewer remaining buffalo bones and so bone pickers began to raid Indian burial grounds. This practice was eventually stopped after some controversy.