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Sodium Bicarbonate

Is sodium bicarbonate allowed in organic processing from any source, or are only some forms acceptable?

By Brian Baker

There are two common processes used to make sodium bicarbonate: the Solvay process and the Trona process. In the Solvay process, limestone is mined and heated to produce carbon dioxide and quicklime (calcium oxide). The carbon dioxide is reacted with a saturated solution of ammonia in salt brine, resulting in the formation of ammonium bicarbonate. Continuous injection of carbon dioxide to the ammonium bicarbonate liquor forms sodium bicarbonate and ammonium chloride. Precipitated sodium bicarbonate is removed from the liquor through filtration.

Trona is a sodium-rich mineral found in deep mines in the Unites States and in other areas. In the Trona process, Trona ore (known chemically as sodium sesquicarbonate) is mined, crushed, and calcined to form sodium carbonate and impurities. The impurities are removed by dissolving the impure sodium carbonate in water and allowing it to evaporate and crystalize. Carbon dioxide gas is percolated through a carbonation tower containing a saturated solution of sodium carbonate, which precipitates out sodium bicarbonate.

Both of these processes were considered by the National Organic Standards Board (NOSB) when sodium bicarbonate was reviewed for inclusion on the National List. The Technical Advisory Panel report concluded that of the two processes, the Trona process would be considered nonsynthetic and the Solvay process would be considered synthetic. In 1995, the NOSB voted to  classify sodium bicarbonate as a nonsynthetic substance, although they did not distinguish between the different production practices. The first publication of the National Organic Program (NOP) regulations in 2002 listed sodium bicarbonate only on §205.605(a), indicating that only nonsynthetic forms are allowed. Under the NOP regulations, OMRI prohibits sodium bicarbonate produced by the Solvay process and allows only sources of sodium bicarbonate obtained through the Trona process.

Revised and updated in May 2016 by OMRI Technical Director Johanna Mirenda. This article was originally published in the Winter 2008 edition of the OMRI Materials Review newsletter.