# Sulfur and Sulphuric acid Most sulphur ends up as sulphuric acid: it is burned to sulphur dioxide and converted to acid, mainly for phosphate fertiliser and metal leaching. Sulphur is a by-product of cleaning oil and gas, so its supply does not respond to acid demand, and when a blockade of the Strait of Hormuz cut Gulf shipments in 2026, the delivered acid price in northern Chile doubled in about seven weeks. Source page: https://www.materialinsights.org/links/sulfur-and-sulphuric-acid/ [Sulfur](https://www.materialinsights.org/commodities/sulfur/) (commodity) and [Sulphuric acid](https://www.materialinsights.org/chemicals/sulphuric_acid/) (chemical): 4 relationships. ## How they are linked ### 1. Sulphur burned to acid *Physical flow · Strong · Sulphur to sulphuric acid* In the contact process, molten sulphur is burned to sulphur dioxide, oxidised over a vanadium catalyst to sulphur trioxide and absorbed into acid; this is the main use of elemental sulphur. - **about 90%** of US sulphur consumed as sulphuric acid, 2025 - **84 Mt** world sulphur production, 2025 Acid is hazardous and costly to ship over long distances, so much of it is made near where it is used, from sulphur shipped in solid or molten form. Burning sulphur releases a lot of heat, which plants recover as process steam or electricity, so a sulphur-burning acid plant is also an energy source for the site. Sources: [USGS](https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-sulfur.pdf); [CRU, Sulphur magazine](https://bcinsight.crugroup.com/2022/09/30/generating-carbonless-energy-from-sulphuric-acid-plants) ### 2. Sulphur supply set by oil and gas *Joint production · Asymmetric · Refining and gas processing yield sulphur* Most sulphur is recovered when refineries and gas plants strip it out of fuels, so output follows oil and gas throughput and environmental rules, not acid demand. - **more than half** of world sulphur used for phosphate fertiliser, its largest use Supply is concentrated where sour gas and large refineries are: China, the US, Russia, Saudi Arabia, the UAE, Kazakhstan, India and Qatar led output in 2025. Because sulphur is a by-product, prices swing widely: the US average unit value rose from about USD 46 a tonne in 2024 to USD 180 in 2025. Sources: [USGS](https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-sulfur.pdf); [Kelewell](https://www.kelewell.de/en/post/surging-sulfur-prices-who-is-choking-the-global-phosphate-fertilizer-industry) ### 3. Smelter acid *Substitution · Medium · Smelter acid competes with sulphur-burnt acid* Non-ferrous metal smelters capture sulphur dioxide from roasting sulphide ores and turn it into acid, which competes with sulphur-burnt acid and needs no sulphur purchase. - **about 6%** of US sulphur production recovered as smelter acid, 2025 - **37.1%** of Chile's acid imports from China, 2025 Smelter acid is made whatever the acid price, so it must be sold or disposed of, and it is traded heavily from China, Peru and Japan to Chile's copper mines. In 2026 China halted acid exports while Gulf sulphur shipping was blocked, so buyers lost both sources at once. Sources: [USGS](https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-sulfur.pdf); [S&P Global Commodity Insights](https://www.spglobal.com/energy/en/news-research/latest-news/metals/042126-no-quick-sulfuric-acid-fix-for-chilean-copper-sector-analysts); [CRU](https://www.crugroup.com/en/communities/thought-leadership/2026/middle-east-conflict-pushes-sulphur-and-acid-prices-to-new-heights/) ### 4. Hormuz and Gulf sulphur *Shared risk · Strong · Gulf supply disruption lifts acid prices* The Gulf is the largest source of seaborne sulphur, so a closure of the Strait of Hormuz removes the feedstock of acid plants across Asia, Africa and Latin America. - **almost half** of seaborne sulphur from the Middle East - **USD 380 a tonne** acid delivered to Mejillones, Chile, 15 April 2026, double its 25 February level After the Middle East war began in early 2026, the delivered acid price in northern Chile doubled in about seven weeks. About a fifth of world copper is produced with acid-based methods, so a sulphur shock spreads from fertiliser to copper. Sources: [S&P Global Commodity Insights](https://www.spglobal.com/energy/en/news-research/latest-news/metals/042126-no-quick-sulfuric-acid-fix-for-chilean-copper-sector-analysts); [CRU](https://www.crugroup.com/en/communities/thought-leadership/2026/middle-east-conflict-pushes-sulphur-and-acid-prices-to-new-heights/) ## For investors ### Key learnings 1. Sulphur supply is fixed by oil and gas processing, so acid prices are set by demand shocks and logistics, and can double in weeks. 2. Acid producers with smelter gas or their own sulphur have a cost advantage in a sulphur spike, while acid makers buying sulphur on spot terms carry the full shock. 3. The Gulf is a single point of failure for sulphur, linking fertiliser and copper leaching costs to Middle East shipping. ### What to track - **Middle East sulphur export price**: Leads acid prices by weeks (Weekly · industry price reports) - **Sulphuric acid price CFR Chile**: Benchmark for traded acid and copper leaching costs (Weekly · S&P Global Platts, Argus) - **China acid and sulphur export policy**: Restrictions tighten acid supply worldwide (As announced · China customs, industry reports) ## For policymakers ### Key learnings 1. India's refinery sulphur and smelter acid are domestic buffers; routing them to fertiliser plants reduces exposure to Gulf supply. 2. Strategic stocks of sulphur are cheaper than stocks of acid, which is hazardous to store in bulk. 3. Sulphur shocks reach the fertiliser subsidy through phosphate costs, so sulphur prices belong in subsidy planning. ### What to track - **India sulphur imports and port arrivals**: Rising imports raise exposure to Gulf disruption (Monthly · DGCIS, port data) - **Domestic refinery sulphur output**: Shows the domestic buffer available to acid makers (Monthly · PPAC, refinery reports) ## India India produced about 3.7 Mt of sulphur in 2025 and imports more for its phosphate and acid plants, for example through Paradip port. Gulf sulphur disruptions therefore raise Indian acid and phosphate fertiliser costs. ## Sources 1. [Mineral Commodity Summaries 2026: Sulfur](https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-sulfur.pdf), USGS (2026) 2. [Surging sulfur prices: who is choking the global phosphate fertilizer industry?](https://www.kelewell.de/en/post/surging-sulfur-prices-who-is-choking-the-global-phosphate-fertilizer-industry), Kelewell (2025) 3. [No quick sulfuric acid fix for Chilean copper sector: analysts](https://www.spglobal.com/energy/en/news-research/latest-news/metals/042126-no-quick-sulfuric-acid-fix-for-chilean-copper-sector-analysts), S&P Global Commodity Insights (2026) 4. [Fertilizers: India import report, April 2025](https://jmbaximarineservices.com/uploads/notifications/other/FERTILIZERS_April - 2025_jmbaxi.pdf), J M Baxi Marine Services (2025) 5. [Generating carbonless energy from sulphuric acid plants](https://bcinsight.crugroup.com/2022/09/30/generating-carbonless-energy-from-sulphuric-acid-plants), CRU, Sulphur magazine (2022) 6. [Middle East conflict pushes sulphur and acid prices to new heights](https://www.crugroup.com/en/communities/thought-leadership/2026/middle-east-conflict-pushes-sulphur-and-acid-prices-to-new-heights/), CRU (2026)