Surging Sulfur Prices: Who Is Choking the Global Phosphate Fertilizer Industry?

In agricultural production, phosphate fertilizers are essential to crop growth and development. What many may not realize is that the starting point of most common phosphate fertilizers is often a pale yellow, brittle crystal or powder — sulfur.

With a global annual output of approximately 70 million tons, around 80% of sulfur supply comes as a byproduct of petroleum refining and natural gas processing, making it deeply intertwined with the global energy landscape. Sulfur acts as the “heart” of the phosphate fertilizer industry, providing an indispensable driving force.

In recent years, pronounced fluctuations in global sulfur prices have been like stones thrown into a lake, creating ripples not only across the fertilizer industry but far beyond it. This article takes an in-depth look at sulfur’s core role in phosphate fertilizer production, traces the journey from one ton of sulfur to finished fertilizer products, and examines how recent sulfur price surges are reshaping every link of the industrial chain.

I. The Core Driving Force: Sulfur — More Than an “Industrial Vitamin” for Phosphate Fertilizers

Modern industrial phosphate fertilizer production is primarily based on the wet-process phosphoric acid route. Its first and most critical step is the decomposition of phosphate rock (mainly fluorapatite) using sulfuric acid, converting water-insoluble phosphorus into soluble phosphoric acid. As such, a stable supply of sulfuric acid is the lifeline of phosphate fertilizer production.

Sulfur is one of the most critical and highest-quality raw materials for sulfuric acid production. In China, sulfur-based acid production is the dominant method. According to industry analysis, in 2024, sulfur-based sulfuric acid accounted for 42.5% of China’s total sulfuric acid output, and it is the preferred acid-generation route for nearly all leading phosphate fertilizer producers.

Compared with acid production based on pyrite and other feedstocks, sulfur-based acid production offers multiple advantages: mature technology, lower energy consumption, better environmental performance, and the ability to recover byproduct steam. A typical sulfur-burning acid plant is not merely an acid source but also an energy hub, as the recovered steam can be used for power generation or heating, significantly reducing overall system energy consumption.

In essence, without stable and cost-effective sulfuric acid, large-scale, high-efficiency phosphate fertilizer production would not be possible. Through sulfuric acid production, sulfur fundamentally unlocks the value of phosphate rock, making its role irreplaceable.

Yet sulfur’s importance goes far beyond phosphate fertilizers. It functions like an “industrial vitamin”, penetrating multiple critical sectors and forming a demand structure characterized by “traditional rigid demand + emerging growth”:

• Agricultural rigid demand:

  Phosphate fertilizer production is the largest application of sulfur, consuming more than half of global sulfur supply. Sulfur is also processed into sulfur suspensions and lime–sulfur solutions for eco-friendly crop protection, or directly added to fertilizers as a sulfur nutrient to improve soils.

  
  

• The starting point of the chemical industry’s “lifeblood”:

  Around 40% of sulfur is used to produce sulfuric acid, which is further consumed in products such as titanium dioxide (3–5 tons of sulfuric acid per ton of TiO₂) and caprolactam (nylon feedstock, ~1.2 tons of sulfuric acid per ton), supporting vast chemical value chains.

  
  

• A rising star in new energy:

  In the lithium iron phosphate (LFP) battery supply chain, about 1 ton of sulfuric acid is consumed per ton of iron phosphate, driving annual sulfur demand growth in this segment above 100%. Research into sulfur applications in solid-state battery electrolytes is also expanding.

  
  

• Other sectors:

  As a rubber vulcanization agent, pharmaceutical ingredient (e.g., sulfur ointments), and a key reagent in hydrometallurgy (such as nickel–cobalt processing in Indonesia), sulfur is deeply embedded across industry and daily life.

  
  

II. From Sulfur to Phosphate Fertilizers: A Precise Relay of Chemistry and Engineering

The transformation from yellow sulfur powder to white fertilizer granules involves a tightly coordinated sequence of chemical reactions and industrial processes.

Stage One: From Sulfur to Sulfuric Acid

This follows the classic contact process:

1. Combustion:

   Solid sulfur is burned with air in a sulfur furnace to produce sulfur dioxide (SO₂).

   
   

2. Conversion:

   Sulfur dioxide reacts with oxygen over a vanadium-based catalyst to form sulfur trioxide (SO₃).

   
   

3. Absorption:

   Sulfur trioxide is absorbed by concentrated sulfuric acid or water to produce commercial sulfuric acid (H₂SO₄).

   
   

Stage Two: From Sulfuric Acid to Phosphoric Acid (Wet-Process Route)

This is the core reaction of phosphate fertilizer production. Concentrated sulfuric acid reacts with ground phosphate rock:

After filtration, crude phosphoric acid and the byproduct phosphogypsum are obtained. For every 1 ton of phosphoric acid (as P₂O₅) produced, approximately 4.5–5 tons of phosphogypsum are generated. The large-scale, high-value utilization of phosphogypsum remains a major environmental challenge for the phosphate chemical industry.

Key Quantitative Relationship: How Much Phosphoric Acid Can One Ton of Sulfur Produce?

From stoichiometry:

• 1 mole of sulfur (32 g) → 1 mole of sulfuric acid (98 g)

• 1 mole of sulfuric acid ultimately yields ~0.6 moles of P₂O₅ (85.2 g)

  
  

Thus, 1 ton of sulfur can theoretically produce about 2.66 tons of pure sulfuric acid, which can then generate roughly 1.6 tons of phosphoric acid (as P₂O₅). Actual industrial yields are slightly lower due to process losses and phosphate rock grade variations.

Stage Three: From Phosphoric Acid to Finished Phosphate Fertilizers

Depending on purity requirements, wet-process phosphoric acid enters different downstream routes:

• Fertilizer-grade phosphoric acid:

  Directly used to produce bulk phosphate fertilizers.

  
  

  • Monoammonium phosphate (MAP) and diammonium phosphate (DAP):

    Neutralizing phosphoric acid with ammonia yields MAP (NH₄H₂PO₄) or DAP ((NH₄)₂HPO₄), depending on ammonia dosage. These are among the most widely used high-concentration fertilizers globally.

    
    

• Industrial-/food-grade phosphoric acid:

  Requires purification (e.g., solvent extraction) to remove impurities such as iron, aluminum, magnesium, and fluorine.

  
  

  • Monopotassium phosphate (MKP):

    Purified phosphoric acid reacts with potassium hydroxide or potassium chloride to produce KH₂PO₄ after crystallization. MKP is a premium, fully water-soluble, chloride-free phosphate–potassium fertilizer widely used in drip irrigation, foliar application, and precision agriculture.

    
    

In addition, sulfur itself can be directly added as a nutrient. Patented technologies allow sulfur powder or aqueous sulfur dispersions to be introduced into ammonium phosphate slurries, producing high-sulfur ammonium phosphate fertilizers that deliver synergistic phosphorus–sulfur nutrition.

III. Shockwaves from Price Volatility: How Rising Sulfur Prices Are Reshaping the Industry Chain

Since 2024, the global sulfur market has experienced a pronounced supply–demand imbalance, with prices surging sharply. By early December 2025, China’s domestic solid sulfur spot prices had risen over 160% year-on-year. This rally reflects a deep resonance between structural supply contraction and rigid demand growth.

Root Causes: A Profound Restructuring of Global Supply and Demand

• Supply tightness:

  Global sulfur supply is highly concentrated and undergoing disruption. The Middle East (Saudi Arabia, Qatar, UAE) supplies over 35% of global sulfur and sets international benchmarks. Russia, once the world’s largest exporter, saw exports plunge from a peak of ~7 million tons due to refinery damage and an export ban imposed in November 2025.

  
  

  Meanwhile, Central Asian producers such as Kazakhstan and Turkmenistan have emerged as new suppliers, with Kazakhstan’s costs only 60–70% of international averages. China, despite annual output of ~12 million tons, remains heavily import-dependent (47%), making it highly sensitive to external shocks.

  
  

• Demand strength:

  China accounts for 38% of global sulfur consumption, driven by two engines: traditional phosphate fertilizer demand and explosive growth in new energy sectors such as LFP batteries and Indonesian wet-process nickel refining (≈30 tons of sulfuric acid per ton of nickel). These sectors compete directly with phosphate fertilizers for sulfur resources.

  
  

Price Reality: Quantified Cost Shock

• Qatar FOB sulfur prices reached USD 400–420/ton by November 2025 (up 140–180% YTD).

• China’s spot prices surged to RMB 3,800–4,000/ton (up over 150%).

• Even cost-advantaged Kazakhstan sulfur imported via Alashankou reached USD 180–210/ton CIF.

  
  

Industry Chain Impact: Cost Transmission and Structural Reshuffling

Impact Area	Key Effects
Phosphate fertilizer producers	Rapid cost escalation, margin compression, reduced operating rates, growing interest in alternative acid routes and phosphogypsum recycling
Agriculture & food security	Higher fertilizer prices raise farmers’ costs; prolonged production cuts may threaten peak-season supply
Related industries	TiO₂, caprolactam, and other sulfuric-acid-intensive sectors face margin pressure
Sulfur market itself	High prices begin to suppress demand; buyers resist purchases, operating rates decline, and the market searches for a new equilibrium

Outlook

Most institutions expect sulfur prices to remain volatile but elevated in the second half of 2025. Seasonal fertilizer demand and winter steam demand support prices, while weak downstream profitability forms a ceiling. The entire value chain must adapt to a new normal of relatively expensive sulfur.

IV. Conclusion

Sulfur, seemingly ordinary, is in fact a super-connector linking minerals, energy, chemicals, and agriculture. Through sulfuric acid, it transforms underground phosphate rock into crop nutrients that sustain global food systems. Amid energy transitions and emerging industries, sulfur’s supply–demand balance is being fundamentally reshaped.

Understanding sulfur’s story reveals not only the industrial foundation behind a bowl of rice, but also the complex interplay of resources, costs, and industrial security in the global economy. Improving resource efficiency (e.g., phosphogypsum recycling) and developing new sulfur sourcing pathways will be essential to meeting this ongoing “sulfur challenge.”