What Is Trona and How Is It Used in Manufacturing?

Trona is a naturally occurring evaporite mineral with the chemical formula Na₃H(CO₃)₂·2H₂O, known more formally as sodium sesquicarbonate dihydrate. Its primary value lies in being the raw material for soda ash (sodium carbonate), one of the most widely used industrial chemicals on Earth. Soda ash goes into glassmaking, detergents, paper production, and dozens of other manufacturing processes, and trona is the cheapest, most energy-efficient way to get it. The mineral itself looks unremarkable, forming pale, translucent or white crystalline masses in ancient lake beds, but the chemistry locked inside it underpins an enormous share of modern industry.

What Trona Actually Is

Trona is sometimes described as “natural soda,” which captures its role but glosses over its chemistry. It is not pure sodium carbonate. Instead, it is a double salt containing both carbonate and bicarbonate ions bound with sodium and water molecules. That mixed composition is reflected in its formal name, sodium sesquicarbonate, where “sesqui” refers to a one-and-a-half ratio of carbonate to bicarbonate. The mineral forms monoclinic crystals and is soft enough to scratch with a fingernail, rating about 2.5 on the Mohs hardness scale. It is water-soluble and strongly alkaline, with a pH around 10.5 when dissolved.¹

Trona belongs to the evaporite family of minerals, meaning it crystallizes when water evaporates from saline or alkaline solutions. It has also been identified in magmatic environments, which broadens the geological settings where it can appear beyond the classic lake-bed scenario.² When freshly mined, trona ore typically contains about 90 percent trona mineral by weight, along with shale, mudstone, and other impurities that must be removed during processing.

How Trona Forms in Nature

The conditions that create trona deposits are surprisingly specific, which is why large deposits are rare even though the ingredients are geologically common. The process begins in a closed or semi-closed basin surrounded by volcanic rock. Groundwater percolates through these volcanic and volcaniclastic sediments, dissolving sodium through silicate hydrolysis. When that sodium-rich, bicarbonate-laden water collects in a lake with no outlet, evaporation under a semi-arid climate concentrates the dissolved salts until trona crystallizes out.³

But volcanism and evaporation alone do not fully explain why trona deposits are so rare. Plenty of closed basins sit atop volcanic rock without ever producing trona. Research into this puzzle suggests that an additional factor is needed: “excess” carbon dioxide from magmatic sources or the decomposition of organic matter. This extra CO₂ shifts the water chemistry in a way that favors trona crystallization rather than other sodium minerals. In essence, the CO₂ acts as a chemical nudge that tips a sodium-rich lake toward the specific carbonate-bicarbonate balance trona requires.⁴

The deposits that resulted from these conditions can be massive. Wyoming’s Green River Basin, the world’s largest known trona deposit, formed roughly 50 million years ago in a vast alkaline lake during the Eocene epoch. Sodium was likely supplied by thermal springs and volcanic tuffs interbedded with the lake sediments, a pattern also documented in Turkey’s Beypazarı Basin, where trona formed in fluvial and lacustrine environments alongside lignite and bituminous shale.⁵ Other notable trona occurrences include deposits in Kenya’s Lake Magadi, China’s Henan Province, and several locations across the East African Rift.

From Raw Mineral to Soda Ash

Trona ore is mined underground, typically using room-and-pillar methods. In Wyoming, the ore beds sit roughly 200 to 500 meters below the surface, and miners extract the trona in horizontal seams that can be several meters thick. Once brought to the surface, the ore enters a refining process designed to strip away the water molecules and bicarbonate portion, leaving behind pure sodium carbonate, or soda ash.

The most common refining route is the monohydrate process. Crushed trona ore is dissolved in hot water, and the resulting solution is filtered to remove insoluble shale and clay. The clarified solution is then heated further, which decomposes the bicarbonate component and drives off CO₂ and water, converting the sodium sesquicarbonate into sodium carbonate monohydrate crystals. Those crystals are separated, dried, and heated one last time to remove the remaining water, yielding anhydrous soda ash. The whole process is energy-intensive but straightforward compared to the alternative way of making soda ash: the Solvay process.

Natural Trona Versus the Solvay Process

Not all soda ash comes from trona. The Solvay process, invented in the 1860s, synthesizes soda ash from salt (sodium chloride), limestone, and ammonia through a series of chemical reactions. As of 2000, roughly 59 percent of worldwide soda ash came from the Solvay process, while about 30 percent was produced from natural sodium carbonate minerals like trona.⁶ The remaining share came from other methods, including processing naturally occurring brine.

The economic competition between these two routes is heavily influenced by geography. Countries sitting on top of large trona deposits, especially the United States, have a built-in cost advantage because mining and refining natural trona requires less energy and produces fewer waste byproducts than the Solvay process. Solvay plants generate substantial volumes of calcium chloride waste and consume more energy per ton of soda ash produced. In regions without trona deposits, however, the Solvay process remains the only practical option, and many plants in China, India, and Europe continue to operate on synthetic routes. Over recent decades, the balance has gradually shifted toward natural soda ash as lower production costs and environmental considerations favor trona-based manufacturing.

Where Soda Ash Goes

Soda ash derived from trona feeds into a surprisingly wide range of industries. The largest single consumer is glassmaking. Soda ash acts as a flux in glass production, lowering the melting point of silica sand so that furnaces do not have to reach extreme temperatures. Without it, producing the flat glass used in windows, automotive windshields, and solar panels would be considerably more expensive and energy-intensive. Container glass for bottles and jars also relies on soda ash as a core ingredient.

Detergent manufacturing is another major consumer. Sodium carbonate serves as a builder in detergent formulations, softening wash water by binding calcium and magnesium ions that would otherwise interfere with surfactants. This allows detergents to clean more effectively, especially in hard-water regions. The chemical industry more broadly uses soda ash as a feedstock for producing sodium bicarbonate (baking soda), sodium silicate (water glass), and sodium phosphates, all of which have their own downstream applications in food processing, adhesives, and water treatment.

The paper and pulp industry also uses soda ash in the pulping process, where it helps break down wood fibers. And in metallurgy, sodium carbonate is used as a flux in refining certain ores. An early epidemiological study of trona miners explicitly noted that trona is “mined from an underground deposit in Wyoming and processed for use in glass, paper, detergent, and chemical applications,” which gives a sense of how long these end-use categories have dominated the industry.¹

Cleaning Up Flue Gas

One of trona’s more specialized industrial uses is in flue gas desulfurization, or scrubbing acid gases from the exhaust of power plants, incinerators, and industrial boilers. In a dry sorbent injection system, finely ground trona or sodium bicarbonate is injected directly into hot flue gas. The heat calcines the trona into a porous, activated form of sodium carbonate with a high surface area. That activated material then reacts rapidly with hydrogen chloride and sulfur dioxide in the gas stream, converting them into sodium chloride and sodium sulfate, which are captured by electrostatic precipitators or fabric filters before the cleaned gas exits the stack.⁷

Trona-based dry scrubbing has gained traction because it avoids the large water requirements and wet sludge waste associated with traditional wet scrubbing systems. The solid byproducts are easier to handle and dispose of. For waste-to-energy plants and smaller industrial boilers in particular, dry sorbent injection with trona offers a simpler, lower-maintenance approach to meeting air quality regulations for acid gas emissions.

An Unexpected Role in Agriculture

Trona, in its sodium sesquicarbonate form, has also been studied as a feed additive for dairy cattle. The idea is that its alkaline nature can help buffer the rumen, the first compartment of a cow’s digestive system, where bacterial fermentation breaks down feed. When cows eat high-grain diets, rumen pH can drop low enough to impair digestion and reduce milk output. Adding a buffering agent like sodium sesquicarbonate aims to stabilize that pH.

A study examining the effects of sodium sesquicarbonate on Holstein cows over a full 308-day lactation found that it did not affect yields of milk, fat-corrected milk, or milk components for most of the lactation period. However, during the final stretch of lactation (days 246 to 308), cows receiving sodium sesquicarbonate produced more milk, more fat-corrected milk, and more protein and fat than control cows.⁸ The results suggest a modest, late-lactation benefit rather than a dramatic across-the-board improvement. In practice, sodium sesquicarbonate and sodium bicarbonate are both used as rumen buffers in the dairy industry, and trona is a natural source of the former.

Health Risks for Miners and Processors

Working around trona carries occupational health considerations that go beyond what you might expect from a mineral that dissolves in water. Trona dust is alkaline enough to irritate the skin, eyes, mucous membranes, and respiratory airways. An epidemiological study of 142 underground miners and 88 surface workers at a Wyoming trona facility found that nonsmokers with measured dust exposure showed a significant decline in a key measure of lung function (the volume of air a person can forcibly exhale in one second) related to respirable dust exposure. Industrial hygiene sampling at that facility found elevated levels of total dust, though respirable dust levels were lower and no free silica was detected.¹

More recent monitoring, however, has identified a separate hazard: respirable crystalline silica in trona mines. The trona ore beds sit within sedimentary sequences that include silica-bearing rock, and mining operations like drilling, blasting, crushing, and conveyor transfers can aerosolize silica particles. Documented silica concentrations in Wyoming’s Green River Basin trona mines have ranged from 20 micrograms per cubic meter to more than 120, with the occupational exposure limit set at 50. Even with improved control technologies, high-risk operations continue to present significant exposure potential.⁹

The control strategies used in trona mines follow a familiar hierarchy: engineering controls such as wet drilling, water sprays, enclosed and filtered equipment cabs, and local exhaust ventilation are prioritized. Administrative controls like worker rotation, regular air monitoring, and maintenance of dust suppression systems layer on top. Personal protective equipment is the last line of defense. The silica hazard is worth noting because it is not inherent to trona itself but to the surrounding geology. Miners working in trona are effectively working through mixed rock, and the silica risk travels with the host formation rather than the target mineral.

Trona Beyond Earth

One of the more intriguing aspects of trona is that it is not exclusively a terrestrial mineral. Sodium carbonate and bicarbonate minerals, including trona, have been identified or inferred on other planetary bodies. Spectroscopic data from NASA’s Dawn spacecraft suggested the presence of sodium carbonate on the surface of the dwarf planet Ceres, and similar evaporite chemistries are hypothesized for the subsurface oceans of icy moons like Enceladus and Europa. On Mars, carbonate minerals have been detected in certain geological formations, though the specific identification of trona versus other sodium carbonates remains uncertain at the resolution available from orbital and rover instruments.

These extraterrestrial occurrences matter because they reinforce a broader point about trona’s formation requirements: alkaline water, dissolved sodium, carbon dioxide, and evaporation. Where those conditions exist, trona or related minerals tend to follow. For astrobiologists, the presence of evaporite minerals is a potential marker for past liquid water activity and habitable conditions, making trona’s signature one small piece of the puzzle in the search for environments that could have supported life elsewhere in the solar system.

Why Trona Deposits Stay Economically Dominant

Given that soda ash can be synthesized from common materials via the Solvay process, it is reasonable to ask why anyone bothers mining trona at all. The answer comes down to cost, energy, and waste. Producing a ton of soda ash from trona uses roughly half the energy of the Solvay process and generates far less solid and liquid waste. The Solvay process produces about a ton of calcium chloride waste for every ton of soda ash, and disposing of or finding uses for that byproduct is a persistent challenge for Solvay plants. Trona-based production generates insoluble tailings (the shale and clay removed during dissolution), but these are chemically inert compared to Solvay waste streams.

The United States, sitting on the Green River Basin’s estimated 100 billion tons of trona, produces more soda ash than any other country and exports significant volumes to markets where local Solvay plants have higher production costs. Turkey’s Beypazarı deposit, while smaller, similarly provides an economic edge in regional markets. As environmental regulations tighten globally and energy costs remain a concern, the cost advantage of natural trona over synthetic production has widened rather than narrowed. Several Solvay plants in Europe and North America have shut down over the past few decades, unable to compete with imported natural soda ash.

This does not mean trona mining is without environmental footprint. Underground mining disturbs large volumes of rock, and the processing plants consume water and energy. Tailings disposal requires careful management, and some operations have explored backfilling mined-out areas with mill tailings to reduce surface disturbance. But on a lifecycle basis, the natural route remains considerably lighter than the synthetic alternative, which is why the global soda ash market continues to shift toward trona-derived production wherever supply lines make it practical.