SOAPSTOCK UTILIZATION, AN ENVIRONMENTAL-AGRICULTURAL BREAKTHROUGH

Ralph S. Daniels, AGROTECH, INC. Sherman, Texas USA

Presented at the 1997 AOCS Annual Meeting

Seattle, Washington May 12, 1997

The most widely practiced method for purifying crude vegetable oils for edible use is the alkali or caustic refining method. The process employs a dilute aqueous solution of caustic soda to react with the free fatty acids present to form soaps. The soaps together with hydrated phosphatides, gums and prooxidant metals are separated from the refined oil as the heavy phase discharge from the refining centrifuge and is known as soapstock.

Since soapstock is an inherent result of the refining process, its disposition is essential to the continuous operation of the refinery. However, with environmental regulation continuing to negatively impact the primary outlet for soapstock, disposition has become increasingly problematic. Compliance threatens to disrupt the supply disappearance balance with, perhaps, serious consequences for those unprepared for the future.

While some soapstock is added to defatted meals or incorporated into animal feeds, most is disposed of by processing in order to recover the fatty acids removed during refining. The process is referred to as acidulation as an acid, usually sulfuric, is used to split the soapstock into its oil and water component parts. The fatty acid or acid oil phase is sold as a feed ingredient. The aqueous or acid water phase is discharged as waste. Herein lies the heart of the problem: disposition of soapstock, one waste product, creates acid water, another waste product - a catch 22 vicious cycle. Acid water is high in biological oxygen demand (BOD), phosphorus and other matter subject to discharge limits or prohibitions. These restrictions have precluded acidulation from use in many parts of the country and the world. With regulation becoming increasingly more strict and enforcement more uniform, conventional acidulation as a disposal channel for soapstock may cease to be viable.

However, a new technology developed by Agrotech allows acid oil to be produced from soapstock without any accompanying waste. A zero-discharge process, it has the potential to dispose of the entire supply of soapstock produced both now as well as in the future.

The technology creates a second, new, coproduct from the acidulation process. All traces of the erstwhile waste are eliminated as the acid water is completely converted into a multinutrient liquid fertilizer. By using process modification, source reduction, philosophy, vegetable oil refining becomes a closed-loop agricultural processing system. Let me now discuss how a simple change or two can bring about such a revolution.

If caustic potash (potassium hydroxide) is used in place of caustic soda (sodium hydroxide) to refine vegetable oils, potassium soaps/soapstock will be formed. Upon acidulation, they will form potassium salts in the acid water, aqueous, phase. Using ammonia or ammonium hydroxide to neutralize the so1ution further enriches it by adding nitrogen. The sodium, which has no nutritive value, has been replaced by potassium and nitrogen, both primary nutrients, and the aqueous phase has been completely transformed into a useful multinutrient liquid plant food. All traces of acid water waste with their attendant environmental issues disappear. Upon analysis the solution will be found to contain: the three primary plant nutrients - nitrogen from plant protein fragments, amino acids, and ammonia, phosphorus from hydrolyzed phosphatides and the phosphoric acid added as a pretreatment to crude oil to facilitate removal of the nonhydratable phosphatides, and potassium from the seed extract and refining caustic; the three secondary plant nutrients- sulfur from the sulfuric acid acidulant, calcium and magnesium both from the precipitated nonhydratable phosphatide complexes and many, if not all of the essential trace element micronutrients (iron, zinc, copper, etc.) naturally present in all seed extracts. These are the very same prooxidant metals requiring removal from the crude oil and put to beneficial use as fertilizer.

Since Agrotech commenced operations in 1995, it has produced more than 10 million pounds of useful fertilizer rather than 10 million pounds of costly, undesirable waste. The fertilizer has been used as is or supplemented in various formulations to grow winter wheat, corn, sorghum (milo), cotton, soybeans, peanuts and coastal Bermuda grass (hay). It has also been used to grow a wide variety of high value horticulture crops. Of note, improved crop response was observed with winter wheat and coastal Bermuda grass, although these were not scientific tests. However in a recent comparative fertility study with cut rose plants conducted under scientific supervision, the crop yield of roses (blooms produced) increased by 14%. Of interest, a similar test conducted with fertilizer produced in collaboration with Central Soya 10 years ago, produced similar results. The results stating that cut rose yields improved by 15% were presented in a paper entitled "Acid Water to Fertilizer, the Daniels Process" at the 1990 AOCS National Meeting in Baltimore. I am delighted to report the recent study confirms the earlier findings.

In conclusion, we believe we have achieved an important breakthrough with the commercialization of the Daniels Fertilizer Process technology. All the available soapstock in the world can be put to beneficial use raising poultry and livestock and growing crops. There is no need to pollute nor risk operational disruption when such an environmenta1ly responsible technology is available to the industry.