How baking soda is made

Industrial baking soda is mined trona or soda ash bubbled with carbon dioxide until crystals fall out.

stations: 6
things upstream: 15
raw sources: 9
steps from the ground: 5

The short version

Baking soda, sodium bicarbonate, is made from sodium carbonate. Soda ash, either mined as trona or made by the Solvay process from salt brine and limestone, is dissolved in water and treated with carbon dioxide. Sodium bicarbonate is less soluble, so it precipitates as crystals that are filtered, dried and packed.

Mine the trona

In Wyoming's Green River basin, the biggest trona deposits are mined underground. Trona is a natural mineral that holds both sodium carbonate and sodium bicarbonate.

Goes in
Trona
Calcine to soda ash

Crushed trona is heated so it gives up water and carbon dioxide and becomes soda ash, which is sodium carbonate. Where there is no trona, plants make soda ash with the Solvay process, using salt brine, limestone and ammonia that is recycled around the plant.

Goes in
Limestone Ammonia Rock salt
Dissolve the soda ash

Soda ash goes into water in large tanks until it forms a strong solution. Insoluble grit from the ore is filtered out first.

Goes in
Soda ash Water
Carbonate the solution

Carbon dioxide gas is bubbled up through towers filled with the solution. Sodium carbonate takes up carbon dioxide and water and becomes sodium bicarbonate, which does not dissolve as well.

Goes in
Carbon dioxide
Crystallize and filter

Sodium bicarbonate comes out of solution as a solid. Filters or centrifuges pull the crystals from the liquid, which is sent back to dissolve more soda ash.
Dry, sieve and pack

The wet crystals are dried gently, because heating above 80 °C would make them start breaking down. Screens sort them into grades from fine powder to coarse granules before bagging.

End of the lineBaking soda Next it goes into pretzel, sparkling water, frozen pizza and 4 more.

Worth repeating

In 1846 two American bakers, John Dwight and Austin Church, opened the first U.S. factory making baking soda from sodium carbonate and carbon dioxide.
An ad campaign that began in 1972 put a box of baking soda in more than half of American refrigerators within a year, though there is little evidence it removes odors.