Cargill’s Newark Salt Works is part of a larger, active solar salt harvesting operation in San Francisco Bay.  While much of the operation has been given over to habitat restoration in recent years a number of solar evaporation ponds remain in operation.


The principle of solar salt harvesting is simple.  Seawater from San Francisco Bay is pumped into the network of ponds.  As the Mediterranean climate of the Bay evaporates the water a concentrated “brine” is left behind.  The brine is pumped into ponds of increasing salinity.  When enough water has evaporated the brine becomes “saturated” and the salt precipitates out.  It can then be harvested and purified for a variety of uses.


The in and outflow from each pond holds it at a “steady state”:  nutrients and salt are provided at rates that do not vary widely within the lifespan of the microorganisms which inhabit the ponds.  This makes the ponds an excellent place to investigate the physiological response of microorganisms to salinity.  Duplicating these conditions using a “chemostat” in the laboratory would be both time consuming and expensive.


For more on the history of salt harvesting in the Bay check out this article from the Ventura County Star, July 21, 2002.  For more information about salt use and harvesting take a look at this article in Wikipedia.


Special thanks to Cargill for allowing us access to the facility, and to the Cargill Salt employees who facilitated this visit.


Aerial view of Cargill’s Newark Salt Works.  The color of the ponds comes from the pigmentation of the microorganisms which inhabit them.  These pigments ranges from green to vibrant pink and orange, the latter colors are a strong indication of the hypersaline nature of these ponds.

Cargill’s Newark Salt Works, California, June 2008

A sampling expedition across 15 solar evaporation ponds in four days to evaluate the influence of salinity on lipid production and D/H fractionation in algae, cyanobacteria, bacteria, and archaea in a natural laboratory.

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fieldwork by Jeff Bowman