Almost all the sulphur (sulfur in American spelling) sold today comes from oil refineries and natural gas plants. It is recovered as a by-product when hydrogen sulphide is removed from fuels, using the Claus process. Mining of native sulphur, once the main source, has largely ended. The United States Geological Survey estimates world sulphur production in all forms at 84 million tonnes in 2025.
How is sulphur made from oil and gas?
Crude oil and natural gas contain sulphur compounds. Fuel specifications and emission rules require them to be taken out, so refineries and gas plants have to recover sulphur whether or not there is a buyer for it. That is the central fact of the sulphur market: supply follows oil and gas processing, not sulphur demand.
Recovery has two parts.
Removing hydrogen sulphide. In a refinery, hydrotreating reacts the sulphur in the oil with hydrogen to form hydrogen sulphide (H2S). Sour natural gas already contains H2S. In both cases the gas is washed with an amine solution, which absorbs the H2S and releases it again as a concentrated stream.
Converting it to sulphur: the Claus process. The process was first patented in 1883 by the chemist Carl Friedrich Claus. According to the United States Environmental Protection Agency, approximately 90 to 95% of recovered sulphur is produced this way. It has a thermal stage and a catalytic stage.
- One third of the hydrogen sulphide is burned with air in a furnace to form sulphur dioxide: 2H2S + 3O2 → 2SO2 + 2H2O. The furnace normally runs at 980 to 1,540°C.
- The sulphur dioxide reacts with the remaining two thirds of the hydrogen sulphide to form sulphur: 2H2S + SO2 → 3S + 2H2O. Part of this happens in the furnace itself, and approximately 65 to 70% of the sulphur is recovered from the condenser that follows it.
- The cooled gas is reheated and passed over a catalyst of activated alumina or titanium dioxide at 200 to 315°C, where the same reaction continues. Sulphur is condensed and removed after each catalytic stage.
The overall reaction is 2H2S + O2 → 2S + 2H2O.
The reaction is an equilibrium and cannot convert all the sulphur. The Environmental Protection Agency estimates that 95 to 97% overall recovery can be achieved, depending on the number of catalytic stages and the reactor temperatures. Plants that have to meet tighter emission limits add a tail gas treatment unit, which brings recovery to as much as 99.9%.
The product leaves the condensers as liquid sulphur, runs to a covered pit, and is pumped to road tankers, rail cars or a forming plant. Recovered sulphur is very pure, commonly sold at 99.8% minimum.
What is the Frasch process?
The Frasch process mines native sulphur by melting it underground. Herman Frasch devised it in 1894 to work deposits in Louisiana and Texas that lay under quicksand and could not be reached by shafts.
Three concentric pipes are sunk into the deposit. Superheated water at about 165°C is pumped down the outer pipe. Sulphur melts at about 115°C, so the hot water melts it in place and the liquid collects at the foot of the well. Molten sulphur is denser than water and will not rise on water pressure alone, so hot compressed air is sent down the innermost pipe to froth it. The lighter froth rises up the middle pipe. The sulphur that reaches the surface is about 99.5% pure and needs no refining.
The method suits deposits in the cap rock of salt domes and in bedded evaporites, at depths of 50 to 800 metres. It uses a great deal of energy: 3 to 38 cubic metres of superheated water are needed for every tonne of sulphur.
Why Frasch mining largely ended
Frasch sulphur dominated world supply for much of the twentieth century. From the 1970s, by-product sulphur recovered from oil and natural gas lowered the price, and a mine that has to heat water to earn its sulphur could not compete with producers who had to recover theirs anyway. The last Frasch mine in the United States closed in 2000, and a Frasch mine in Iraq closed in 2003. The process survives on a small scale, including in Poland.
Other sources of sulphur
Two other sources appear in production figures counted as "all forms".
- Smelter acid. Copper, zinc, lead and nickel are mined as sulphide ores. Smelting them gives off sulphur dioxide, which is captured and converted directly into sulphuric acid. In the United States, by-product sulphuric acid represented about 6% of sulphur production in all forms in 2025.
- Pyrites. Iron pyrites are roasted to make sulphuric acid in some countries, China above all.
Where is sulphur produced?
The USGS Mineral Commodity Summaries 2026 gives the following estimates for 2025, in thousand tonnes of sulphur content, all forms.
| Country | Sulphur production, 2025 estimate (thousand tonnes) |
|---|---|
| China | 19,000 |
| United States | 8,100 |
| Russia | 7,500 |
| Saudi Arabia | 7,200 |
| United Arab Emirates | 6,300 |
| Canada | 5,000 |
| Kazakhstan | 4,800 |
| India | 3,700 |
| Qatar | 3,100 |
| Republic of Korea | 3,100 |
| World total | 84,000 |
World output in 2024 was 83.9 million tonnes. The list is a list of oil refiners, sour gas producers and metal smelters. The USGS points out that sulphur is often recovered far from where the oil was produced: sulphur from Saudi Arabian crude may be recovered at a refinery in the United States. In the United States itself, elemental sulphur was recovered at 81 plants in 2025, with Louisiana and Texas accounting for about 54% of domestic output.
China is the largest producer and also the largest importer, because its phosphate fertiliser industry uses more than the country recovers. Exporters are the countries with large sour gas and refining output and little home demand: the Gulf states, Kazakhstan, Russia and Canada.
The forms sulphur is sold in
Sulphur leaves the recovery unit as a liquid. What happens next depends on how far it has to travel.
- Molten. Kept hot and shipped in heated tankers, rail cars and ships to acid plants with tanks to receive it. No forming cost and no dust. See liquid sulphur.
- Granular. Built up into rounded beads in a drum or fluid bed. Tough, with little dust, and the standard form for ocean cargoes. See granular sulphur.
- Prilled and pastilled. Droplets solidified in water or air, or on a cooled steel belt. Uniform in size. See prilled sulphur.
- Lump. Liquid sulphur poured into blocks, left to set, then broken up. Cheapest to make and the dustiest to handle. See lump sulphur.
Block storage is also how producers hold sulphur they cannot sell; large stockpiles of this kind stand in Alberta, Canada. What buyers do with the product is covered in our guide to what sulphur is used for.
How sulphur is traded
Formed sulphur moves in bulk vessel parcels, FOB the load port or CFR the discharge port, mostly to sulphuric acid plants at phosphate fertiliser and metal leaching sites. Because supply does not respond to price, prices swing widely; current levels are on our dated sulphur price page. Contracts specify purity, moisture, ash, acidity, organic carbon, and size and fines for formed product.
CBIL brokers sulphur between a named producer or seller and a named buyer, with quality and weight certified by an independent inspector such as SGS or Intertek at loading.
Request a sulphur quote with the form, quantity and discharge port.