Most of the baking soda sold in stores comes from mining natural mineral deposits buried deep underground, primarily in the western United States. A smaller share is manufactured synthetically through a nineteenth-century chemical process still used in parts of Europe and Asia. Either way, the familiar white powder in your kitchen started its journey millions of years ago as dissolved minerals in ancient lake waters, or as salt, limestone, and ammonia fed into industrial reactors.
Ancient Natron and the Earliest Uses
Humans have been collecting sodium bicarbonate and its chemical relatives for thousands of years, long before anyone called it “baking soda.” In ancient Egypt, the mineral natron was harvested from dry lake beds in the Wadi Natrun valley, a depression west of the Nile Delta where evaporating waters left behind crusts of mixed salts. Natron typically contains sodium carbonate, sodium bicarbonate, and smaller amounts of chloride and sulfate impurities, and it played a central role in the Egyptian mummification ritual, serving as a powerful desiccant to dry corpses before wrapping.1PubMed. Raman spectroscopy of natron: shedding light on ancient Egyptian mummification Egyptians also used natron for cleaning, glassmaking, and as a kind of early toothpaste. The word “natron” itself is the root of the chemical symbol Na for sodium.
For most of recorded history, people who wanted soda-like compounds simply gathered them from evaporite deposits around alkaline lakes and springs. That changed in the late eighteenth century, when growing demand from soap and glass industries outstripped what natural collection could supply, and chemists began looking for ways to make the stuff from scratch.
The Green River Formation and Its Vast Mineral Deposits
The single most important source of baking soda in North America is a geological formation laid down roughly 50 million years ago during the Eocene epoch. The Green River Formation stretches across parts of Wyoming, Colorado, and Utah, and it holds the largest known sodium carbonate evaporite deposits in the geologic record.2Earth-Science Reviews. The Green River salt mystery: What was the source of the hyperalkaline lake waters? During the Eocene, a series of large inland lakes occupied basins in what is now the intermountain West. These lakes had no outlets to the sea. As the climate shifted and water evaporated, dissolved minerals concentrated and eventually crystallized out of the lake water, building up thick layers of evaporite minerals over millions of years.
Two minerals in the Green River Formation matter most for baking soda production. Trona, found primarily in the Bridger basin in Wyoming, is a combination of sodium bicarbonate and sodium carbonate with water bound into its crystal structure. Nahcolite, found mainly in the Piceance Creek basin of northwestern Colorado, is essentially pure natural sodium bicarbonate. The nahcolite deposits there occur as disseminated aggregates, nodules, and bedded layers within oil shale, and the mineral-bearing zone can be over a thousand feet thick in places.3U.S. Geological Survey. Nahcolite resources in the Green River Formation, Piceance Basin, northwestern Colorado
What made these ancient lakes so mineral-rich is still debated among geologists. Large modern trona deposits, like those at Lake Magadi in Kenya and Searles Lake in California, are associated with volcanic activity and sodium-bicarbonate-rich hot spring waters flowing into the lake. The Green River deposits, however, lack nearby volcanic sources. One hypothesis suggests that bicarbonate-rich waters drained northwestward from a zone of volcanic activity in what is now central Colorado, but field evidence has not yet confirmed those ancient flow paths.2Earth-Science Reviews. The Green River salt mystery: What was the source of the hyperalkaline lake waters? What is clear is that changing water volume, evaporative concentration, and seasonal temperature swings drove recurring cycles of mineral deposition at the basin center.4Geosites. Recurring lacustrine depositional successions in the Wilkins Peak Member, Green River Formation As these lakes became hypersaline, nahcolite and halite crystallized at the deepest part of the basin while mudflats formed along the margins.5Geosites. Spatial and temporal cycle variations in the Eocene Lacustrine Green River Formation, Piceance Creek Basin, Colorado
How Trona Gets Mined and Turned Into Baking Soda
Southwest Wyoming’s Green River basin holds the world’s largest trona deposit, and several large mines operate there, some reaching more than 1,500 feet below the surface. Mining trona is conventional underground mining: workers blast and extract the mineral ore, then haul it to the surface for processing. The raw trona is not something you would put in a recipe. It needs to be refined into either soda ash (sodium carbonate) or baking soda (sodium bicarbonate), depending on the intended market.
The refining process generally works in a few broad steps. Crushed trona ore is heated, which drives off water and carbon dioxide, converting the trona into a crude form of soda ash. That crude material is then dissolved in water, filtered to remove insoluble impurities like shale and clay, and recrystallized to produce pure soda ash. To make baking soda specifically, manufacturers bubble carbon dioxide gas through a solution of soda ash. The COâ‚‚ reacts with the dissolved sodium carbonate to form sodium bicarbonate crystals, which are collected, dried, and packaged. In a sense, the process takes a mineral that already contains sodium bicarbonate, strips it apart, purifies it, and reassembles it.
Nahcolite from the Piceance basin in Colorado offers a more direct route, since it is already sodium bicarbonate in mineral form. Some operations dissolve nahcolite underground by injecting hot water, pumping the brine to the surface, and crystallizing out the product. This solution-mining approach avoids much of the heavy underground infrastructure required for trona, though it brings its own engineering challenges.
The Solvay Process and Synthetic Baking Soda
Not every country sits atop a 50-million-year-old evaporite deposit. For regions without accessible natural trona or nahcolite, the alternative has been synthetic production, dominated since the 1860s by the Solvay process. This method, developed by the Belgian chemist Ernest Solvay, uses salt (sodium chloride), limestone (calcium carbonate), and ammonia as feedstocks. In broad strokes, the process dissolves salt in water, saturates the brine with ammonia, and then passes carbon dioxide through it. The COâ‚‚ reacts with the ammonia and water to produce ammonium bicarbonate, which in turn reacts with the dissolved salt to form sodium bicarbonate crystals. Those crystals can be sold as baking soda directly, or heated further to yield soda ash.
The Solvay process replaced an even older and dirtier method. Before Solvay, the Leblanc process had been the main synthetic route since the late 1700s. Nicolas Leblanc’s procedure used common salt as a raw material but produced such severe pollution, including emissions that contributed to acid rain, that it prompted England to pass some of the earliest environmental protection laws.6Indian Journal of Chemical Technology. Sodium Carbonate – From Natural Sources to Leblanc and Back The Solvay process was a significant improvement in efficiency and cleanliness, but it still carries meaningful environmental costs, which have shaped where and how baking soda is produced today.
Environmental Tradeoffs
The Solvay process generates large volumes of liquid and solid waste. Because a single factory produces so much of this waste, it usually cannot be stored in a conventional disposal site and is instead discharged into rivers, lakes, or the sea. At one Austrian Solvay factory producing about 164,000 tons of soda ash per year, roughly 40,000 tons of solid waste were discharged annually into a nearby lake.7Journal of Cleaner Production. Cleaner production in the Solvay Process: general strategies and recent developments That waste stream includes calcium chloride, unreacted salt, and calcium carbonate mud. In countries with strong environmental regulations, managing this waste adds significant cost and complexity.
Mining natural trona is generally considered to have a lower environmental footprint than the Solvay process. The ore is already close to the desired chemistry, so less energy and fewer chemical inputs are needed to refine it. There is no ammonia to recycle and no calcium chloride slurry to dispose of. That said, underground mining has its own impacts: land disturbance, energy-intensive extraction, and the carbon dioxide released during the heating stage of refining. Neither route is impact-free, but the availability of massive natural deposits in Wyoming has given the United States a cost and environmental advantage in soda ash and baking soda production. Most synthetic Solvay plants that once operated in North America have closed over the past several decades, unable to compete on price or environmental compliance with mined trona.
Why Wyoming Dominates the Global Market
The Wyoming trona deposit is not just large; it is the most economically accessible deposit of its kind anywhere. The trona beds are thick, relatively uniform, and lie at a depth that is challenging but manageable with modern mining techniques. Several companies operate mines in the region around Green River, Wyoming, and together they supply the majority of the soda ash produced in the United States, much of which is exported. The U.S. is one of the world’s largest exporters of natural soda ash precisely because of this single geological inheritance.
China, Turkey, and several other countries also produce soda ash and baking soda, with Turkey drawing on its own natural trona deposit at Lake Beypazarı. China has historically relied more heavily on synthetic Solvay production, though it too has been developing natural soda ash resources. The global market has been gradually shifting toward natural sources where they exist, largely because of the cost and environmental advantages, but synthetic production remains essential in regions without accessible deposits.
Is the Baking Soda in Your Kitchen “Natural”?
If you buy a major brand of baking soda in the United States, it almost certainly originated as mined trona from Wyoming. The dominant U.S. producer has long marketed its product as naturally sourced, and for practical purposes it is: the sodium bicarbonate molecule in the box traces its lineage to a mineral deposit rather than a chemical reactor. But “natural” here is a somewhat loose label. The raw ore undergoes significant industrial processing before it becomes the fine white powder in the orange box. It is dissolved, purified, recrystallized, and dried in a series of factory steps. The end product is chemically identical regardless of whether it started as trona, nahcolite, or Solvay-process brine. No lab test can distinguish naturally sourced baking soda from synthetic baking soda, because they are the same molecule with the same purity.
This matters if you are trying to make an environmental or health distinction at the store shelf. The environmental difference lies in how the product was made, not in what it is. And the health profile is identical either way: sodium bicarbonate is sodium bicarbonate. Some specialty brands market themselves as coming from nahcolite rather than trona, emphasizing the even more “direct” natural origin, but the chemical result is the same.
What Happens When Baking Soda Gets Hot
One reason baking soda is so useful in cooking is that it decomposes when heated. Above about 120°F (50°C), sodium bicarbonate starts to break down into sodium carbonate, water, and carbon dioxide gas. In baking, that released CO₂ is what creates the bubbles that make batter rise. The reaction speeds up with temperature, and by the time your oven reaches typical baking temperatures, the decomposition is vigorous and fast. Research on the thermal breakdown of sodium bicarbonate has found that the decomposition follows a predictable pattern controlled by the chemical reaction rate, with an activation energy of about 20.5 kilocalories per mole.8Chemical Engineering Communications. Thermal Decomposition of Sodium Bicarbonate At very high temperatures, around 600°F, the material begins to sinter and behave differently.
This thermal instability is also the reason baking soda works differently from baking powder. Baking soda needs an acid (like buttermilk, yogurt, or lemon juice) to react at lower temperatures. Without that acid, it mostly just sits in the batter until heat drives the decomposition. Baking powder contains its own built-in acid, so it reacts as soon as it gets wet, with a second reaction when heated. Both products rely on the same underlying chemistry of sodium bicarbonate releasing COâ‚‚, but the trigger differs.
Industrial Uses Beyond the Kitchen
Baking soda’s journey from mine to market does not end at the grocery store. The majority of sodium bicarbonate produced worldwide goes to industrial applications rather than cooking. It is used as a flue gas scrubber in power plants and waste incinerators, where it reacts with acidic gases like sulfur dioxide and hydrochloric acid to neutralize them before they leave the smokestack. It serves as a feedstock for producing soda ash, which is essential for glassmaking, detergent manufacturing, and water treatment. It is used in animal feed as a rumen buffer for dairy cattle, in fire extinguishers, in water treatment to adjust pH, and in pharmaceutical manufacturing as an antacid ingredient.
The sheer variety of applications explains why global production is measured in the millions of tons. Most of that tonnage is soda ash rather than baking soda specifically, but the two are chemical siblings that convert back and forth with relative ease. Add COâ‚‚ to soda ash and you get baking soda. Heat baking soda and you get soda ash plus COâ‚‚ and water. This interconvertibility means that the same mine can serve wildly different markets depending on how the ore is processed downstream.
Why Alkaline Lakes Keep Making These Minerals
The Green River Formation is the most famous source, but it is far from the only place where sodium bicarbonate minerals form. Alkaline and soda lakes around the world continue to precipitate trona and related minerals today, from East Africa’s Rift Valley lakes to Searles Lake and Owens Lake in California. The recipe is always the same: a closed basin with no drainage to the ocean, sodium-rich inflow water (often from volcanic or hydrothermal sources), and enough evaporation to concentrate the dissolved minerals past their saturation point. When water evaporates faster than it flows in, whatever was dissolved in it gets left behind as mineral crusts and beds.
Lake Natron in Tanzania and Lake Magadi in Kenya are modern examples of this process in action. Their shorelines are rimmed with trona and other sodium carbonate minerals, and the waters are so alkaline they can burn unprotected skin. These lakes offer a living analogue for what the Green River lakes may have looked like tens of millions of years ago. Studying them helps geologists understand the conditions under which the Green River deposits formed, including the still-unresolved question of exactly where all that sodium and bicarbonate originally came from.2Earth-Science Reviews. The Green River salt mystery: What was the source of the hyperalkaline lake waters? Whether the source was distant volcanic activity, deep groundwater circulation, or some combination, the legacy of those ancient lakes is the vast mineral warehouse that supplies your kitchen today.