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Specialty Chemicals

Can synthetic soda ash survive?

The iconic 160-year-old Solvay production process is on the ropes, but a chemistry-driven comeback is not possible

by Alex Scott
February 26, 2023 | A version of this story appeared in Volume 101, Issue 7


Solvay's soda ash plant in Rosignano, Italy.
Credit: Birgit Franke
Solvay is developing a version of its synthetic soda ash process that it hopes will cut carbon dioxide emissions and solid waste at its plants, including this one in Rosignano, Italy.

The self-taught chemist Ernest Solvay turned the sodium carbonate industry on its head in 1861 when he discovered a one-step process using brine, limestone, coking coal, and ammonia to make the chemical, which is known in the industry as soda ash. Solvay’s approach supplanted the less efficient two-step process introduced in 1791 by the French chemist and surgeon Nicolas Leblanc.

The white, powdery inorganic compound is used more than ever in the production of glass, textiles, detergents, paper, silicates, and, more recently, lithium carbonate for lithium-ion batteries.

And Solvay’s process is still the dominant production technology. Around three-quarters of the 64 million metric tons (t) of soda ash produced worldwide in 2022 was made using some version of this synthetic method. The rest came from trona, a naturally occurring ore composed of sodium carbonate and sodium bicarbonate.

The Solvay process has a problem, however: it is extremely energy intensive, releasing large amounts of carbon dioxide and generating potentially harmful solid waste. In Europe, where energy costs are high and greenhouse gas emissions may soon come at a price, the Solvay process looks especially prohibitive.

There’s not a net increase in synthetic production volumes, largely because of the environmental impact issue.
Alasdair Warren, CEO, WE Soda

In its current state, synthetic soda ash is a bad fit for the chemical industry’s ambition to transition to zero carbon emissions. But trona, which is present in commercially viable deposits in China, Turkey, and the US, is cheaper and has a far smaller carbon footprint. As a result, trona is steadily gaining market share. More than 160 years after he introduced it, Ernest Solvay’s synthetic process is on the ropes.

“It’s already a challenge for European producers,” Marguerite Morrin, executive director, soda ash, at Chemical Market Analytics, said in a September 2022 market update video. Of the 70 or so synthetic soda ash plants operating worldwide, 16 are in Europe and Turkey.

In addition to having to soak up the recent spikes in energy prices in many parts of the world, synthetic soda ash producers have significant raw material costs, including for coking coal, limestone, and sodium chloride.

Notably, about three-quarters of synthetic soda ash producers depend on coal for their process. This has proved an issue for some producers in Europe, as the European Union’s August 2022 ban on imports of Russian coal has pushed up prices and made sourcing coal difficult. The European spot price of coal is triple what it was before Russia invaded Ukraine.

The high carbon footprint of the Solvay process—1 t of carbon dioxide is generated for each ton of soda ash produced—is another problem for European producers. They expect that in the next few years they will lose their exemptions and be exposed to the full cost of Europe’s emissions trading scheme, which currently puts a price on CO2 of about $106 per metric ton. At that rate, a synthetic soda ash producer with a 100,000 t per year plant would be charged about $11 million annually.

Staging a synthetic comeback

Europe’s synthetic soda ash producers have responded to the new as well as the impending costs by battening down the hatches and trying to reduce emissions. “If we want to be competitive in Europe we need to get rid of CO2 emissions,” says Philippe Kehren, president of soda ash for Solvay, which is still the world’s largest soda ash producer. Solvay also mines trona in the US.

It is a classic case of chemical companies having to either adapt and innovate or fail, says Bernd Elser, a managing director and global lead for chemicals at the professional services firm Accenture.

“The synthetic soda ash production process is one of a series of fundamental chemical processes—including, for example, the Haber-Bosch synthesis of ammonia—which are challenged by the industry’s shift towards net-zero greenhouse gas emissions,” Elser says. “There will be a wave of innovation in response, and there is significant potential for improvement. Very well-established chemical processes may have to be modified or potentially even completely reinvented.”

Solvay says it is developing a low-​carbon synthetic soda ash process. About two-thirds of the greenhouse gases emitted during production are a result of steam generation. Focusing on this energy component, Solvay estimates that it can cut its total greenhouse gas emissions by 20% as soon as 2025. Plans include replacing some of the coal the firm uses to power its soda ash plants in Bulgaria, Germany, and France with biomass or another form of renewable energy.

The other one-third of soda ash emissions results from the use of coal or other fuels in the chemical reaction itself. To lower these emissions, Solvay is developing an electrochemical soda ash process. “The chemistry equations remain the same. What is different is the way we recycle the ammonia,” Kehren says. “It is the next generation of the process—we call it Solvay 2.0.” The company is testing this process at its complex in Dombasle-​Sur-Meurthe, France, and plans to roll it out across other plants in the next few years.

Advantages wouldn’t stop at carbon emissions: The electrochemical process also has the potential to consume substantially less water, brine, and limestone, and it generates little in the way of by-​products, such as calcium chloride, Kehren says. Such technology could help ease concerns surrounding Solvay’s plant in Rosignano, Italy, where discharges from the facility have turned the local beach white and could be affecting public health in the community.

Benefits of trona

Price leader

The cost of making soda ash from trona is far less than making it synthetically


Solution mining of trona


Traditional mining of trona


Cheapest Solvay process in Europe


Solvay process in China

About $250:

Solvay process in India


Most expensive producers in Europe

Source: WE Soda. Prices are per metric ton

Even with the innovations, soda ash production costs remain so high and environmental constraints so strict that major capacity expansions are not being considered in Europe. “Fundamentally, there’s not a net increase in synthetic production volumes, largely because of the environmental impact issue,” says Alasdair Warren, CEO of WE Soda, a London-based firm that describes itself as the world’s largest producer of natural soda ash, with plants in Turkey and Green River, Wyoming.

In contrast with synthetic soda ash production, trona mining emits between 0.3 and 0.7 t of carbon dioxide per ton of soda ash, depending on the quality of the trona, Accenture’s Elser says.

WE Soda claims to be on the low end of that range because, rather than mining trona in a traditional way, it extracts the mineral by drilling bore holes and bringing up the ore in an aqueous solution before dehydrating it. It’s a technique Solvay hopes to apply commercially in about 5 years. “Solution extraction is about a third of the energy intensity of synthetic,” Warren says. The synthetic method also uses about four or five times as much process water per ton of soda ash as natural production, he says.

Solution extraction also trumps conventional underground trona mining, according to Warren. “While a conventional trona mine may employ about 500 people, about half of the employees will be working underground—something that solution extraction does not require,” he says.

Warren estimates that WE Soda’s average production costs were about $50 per metric ton in 2021. In the same year, he says, costs to produce soda ash based on trona conventionally mined in Green River were about $100 per metric ton; costs were over $150 per metric ton for synthetic production in Europe, even before accounting for carbon emission expenses.

Natural soda ash can also fetch a higher price because it is greener. There is a premium of $30–$40 per metric ton, particularly in Europe, because purchasers are focused on its environmental impact, Warren says. “It is our view that over the course of the next 3 or 4 years that differential will become greater,” he says.

As a result of the cost difference, most new soda ash production capacity is based on trona. Trona mining is set to expand rapidly in China, where one large project, with expected production of 8 million t per year, is planned, according to Chemical Market Analytics.

An antiquated black-and-white photo of a man.
Credit: Getty Images
Ernest Solvay's 160-year-old process is still the dominant route for making soda ash.

Companies mining trona in Wyoming are planning to collectively increase production by about the same amount, Morrin said in the video. These are “the biggest expansions I think we have seen in decades,” she said.

Solvay, Tata Chemicals, and WE Soda are among the firms mining trona in the state. Solvay disclosed in November 2022 that it had resumed a $200 million project to expand production there by 600,000 t per year and reduce its emissions per ton of product. Wyoming has billions of tons of trona deposits, enough for hundreds of years of supply, producers say.

WE Soda already produces about 5 million t per year of natural soda ash in Green River using solution extraction. The firm plans to increase production there by 3 million t per year. It plans to more than double its overall production by 2030, to about 11 million t per year, investing about $4 billion in projects in Green River and Turkey. The company is able to make these big investments because of its strong profitability, Warren says.

One place synthetic soda ash production is still expanding is India, which imports about 20% of the material it needs. Although costs are substantially less than in Europe and no costs are associated with carbon emissions, the region’s producers are focused on supplying the local market rather than exporting, says Manu Jain, general manager of the Indian synthetic soda ash producer GHCL.

GHCL plans to build a 500,000 t per year synthetic soda ash plant in Gujarat at a cost of about $430 million, Jain says. There would be a dash to natural production if trona deposits were discovered in India. But in the absence of such a find, synthetic soda ash production in India will continue, he says.

In contrast to India, China has ample domestic supply and is a net exporter, accounting for as much as 45% of the global supply, Jain says. The country’s synthetic producers will have to compete with the new domestic trona mining, however.

If we want to be competitive in Europe we need to get rid of CO2 emissions,
Philippe Kehren, president of soda ash, Solvay

European synthetic producers are luckier. They are somewhat protected from trona-based competition because it is expensive for natural soda ash producers to ship their product to the region, Elser at Accenture says. As a result, he says, even Europe’s high-cost synthetic soda ash producers are in a position to prosper.

The salve of demand

Another saving grace for synthetic soda ash producers, especially the highest-cost firms in Europe, is that the market is tight and expected to stay that way for at least several years. Demand for soda ash is growing 2–3% annually—or by more than 1 million t per year—thanks to double-​digit percentage growth in demand for glass to make solar panels, lithium carbonate to use in lithium-ion batteries, and sodium bicarbonate to remove sulfur oxides from flue gas.

Despite trona’s lower cost of production, it is unlikely that capacity will expand quickly, because everywhere it is mined several years are required to secure permits and implement projects. The emergence of new companies mining or drilling for trona is also unlikely because the approach requires a huge amount of capital and know-how, Warren says. Since trona is found only in the US, Turkey, and China, new natural soda ash producers would be restricted to those countries.

Moreover, natural soda ash producers are selling all their product and have no incentive to undercut the price set by higher-cost synthetic firms, Warren says. Ultimately, he says, synthetic product cannot disappear because the world needs it.

What could still tip the Solvay process into oblivion are carbon emission fees such as those planned for Europe. But experts think that even these costs might be avoided. The synthetic soda ash process could achieve carbon emission levels similar to those of trona-based production if all potential improvements are implemented, Accenture’s Elser says.

Kehren is confident that Solvay will cut the emissions of its synthetic process, which would enable it to hang on and even thrive in Europe and beyond. With Solvay 2.0 in place, he says he “absolutely” expects the synthetic soda ash business to shift from cost cutting to expanding output once again. “Once we have the new process,” he says, “we will have a solution to source energy with a low-carbon content, and synthetic will come back.”




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