Use of spent bleaching earth for economic and environmental benefit
Bleaching earth that has been used to remove the color pigments and impurities from edible oil typically contains entrained oil in the range of 30 to 50% by weight.
This spent bleaching earth is susceptible to spontaneous combustion; consequently, there are few practical uses for it, and handling and disposing of spent bleaching earth is a fire risk, an operating expense, and a source of environmental regulatory concerns—not to mention a significant cost due to the value of the oil that is lost.
This article describes how mixing the spent bleaching earth with salt can eliminate the spontaneous combustion problem while providing a high-demand salt-lick product for livestock.
Since the advent of using clay to adsorb color pigments and impurities from edible oil, processors have been confronted with the problem of spent earth disposal. Typically, spent bleaching earth contains entrained oil in the range of 30 to 50% by weight. The entrained oil is in the form of a thin film spread over the immense surface area provided by the clay particles. Upon exposure to air, rapid oxidation of the oil film occurs and sufficient heat is generated to cause spontaneous combustion. Consequently, the most common method of spent earth disposal is to haul and bury it at a solid waste disposal site. Handling and disposing of spent earth is a fire risk, an operating expense, and a source of environmental regulatory concerns. In addition, the value of the oil that is lost is a significant cost.
For more than 100 years, ideas about practical uses for spent bleaching earth have been originated and tried without much success. Integrated oilseed processors and edible oil refiners have had limited success in adding some spent bleaching earth to meal by taking advantage of the allowable use of clay as a flow aid. Due to problems involving safe handling and uniform blending, the addition-to-meal practice is limited. There is some adding of spent bleaching earth to livestock feed in several countries, but the risk of spontaneous combustion is typically a barrier.
A new solution with positive feedback
In 2011, the author originated the idea that salt could be added and mixed with spent bleaching earth to eliminate the spontaneous combustion problem and provide a high-demand salt-lick product for livestock. A provisional patent was filed to protect the idea and to provide the time for validation. During the summer of 2012, experimental work was conducted to verify that the hydroscopic properties of salt, together with the dilution effect, would eliminate the spontaneous combustion problem with spent bleaching earth. The experimental work was carried out over a week using spent bleaching earth that came directly from an edible oil processing plant (Fig. 1). It was found that salt content as low as 35% would eliminate spontaneous combustion. To provide an additional safety factor, 45% salt addition was established as the minimum.
Fig. 1. Experimental work was conducted by the author using spent bleaching earth that came directly from an edible oil processing plant.
After the experimental work was completed, filing was initiated for a regular patent under the protocol of the international patent agreement. Following successful review of the patent application by the international board, applications have subsequently been filed in most of the livestock-producing countries of the world.
In June 2014, salt-lick products in block and granular form were produced for trial by five cattle producers in the US States of Colorado, Missouri, and Louisiana (Figs. 2 and 3). The feedback from these trials was universally positive. The inventor had no doubt about the expected outcome given his experience:
as the son of a Colorado cattle rancher who used salt-lick products for cattle;
working for 50 years in all aspects of the edible oil processing industry;
monitoring the attraction of cattle to lick spent bleaching earth at a pasture site used for spent bleaching earth disposal. (While anecdotal, 38 years of observation revealed that the cattle involved thrived in terms of health, weight gain, and glistening coats.); and
interacting in recent years with livestock nutritionists focused on the significance of metabolizable energy.
Fig. 2. The author mixes the products produced for the trial.
Fig. 3. The trial product was formulated to meet each user’s specifications with respect to the inclusion of minerals and/or protein meal.