What to Do with Spent Bleaching Earth? A Review
Albert J. Dijkstra
Abstract
Abstract Animal fats and cold‐pressed vegetable oils hardly need bleaching but when vegetable oils started to be produced by solvent extraction, the resulting oils were too dark to sell as such. That also holds for palm oil. Bleaching these oils with bleaching clay solved their color problems but led to the problem of spent earth disposal. Many ways of treating spent earth and ways of disposal have been suggested and/or developed in the past. They will be reviewed in this paper. Given the recent observation that slurrying spent bleaching earth with crude oil inhibits the deterioration of the residual oil in the earth, leads to the conclusion that, for an integrated oil mill‐cum‐refinery, the best way of spent bleaching earth disposal is the recycling of the earth to the solvent extractor, whereas stand‐alone refineries are advised to sell their spent earth to chicken feed manufacturers. In future, a high‐temperature hydrolysis process that can treat all kinds of fatty waste may become an attractive means of disposal as well.