"Rotten Eggs": The hidden role of sulfur in the global economy

Sulfur, the element behind the smell of rotten eggs, quietly underpins food, metals, batteries, and data – and right now it is flashing red for the global economy.

Rotten eggs and burning stone

Sulfur (or sulphur), atomic number 16, is one of the most common building blocks of matter: it’s the tenth most abundant element in the universe by mass and about the 16th most common in the earths crust Earth. It appears in volcanic deposits and hot springs, but on our planet it usually turns up bound into sulfide and sulfate minerals rather than as bright yellow chunks on the surface. For most of human history, people knew it as “brimstone” – burning stone – because it burns with a blue flame and produces a choking, acrid smell. That rotten‑egg signature comes from hydrogen sulfide gas, which is toxic at high concentrations but also a key intermediate in today’s sulfur economy.

If you follow that smell through modern industry, you discover an uncomfortable truth: the global economy runs on sulfur, but almost nobody is paying attention to how fragile that sulfur supply chain has become.

The backbone acid of industrial civilisation

Almost all elemental sulfur today is not mined for its own sake but stripped out as a contaminant from sour oil and gas – fossil fuels that contain significant sulfur. Refineries and gas plants remove this sulfur to meet air‑quality rules; they convert hydrogen sulfide (H₂S) into elemental sulfur using the Claus process, and that yellow sulfur then feeds the global sulfuric acid industry.

Sulfuric acid is the central processing acid of the industrial world. It is used to:

· Digest phosphate rock into fertilizer.

· Leach copper, nickel, and cobalt from ores.

· Refine lithium and other battery materials.

· Manufacture a vast range of bulk chemicals, from detergents to pigments

Industry analysts routinely describe sulfuric acid production as a proxy for industrialisation: more acid means more fertilizer, more steel, more chemicals, and more cars. That rule of thumb still holds. The global sulfuric acid market was worth about 35 billion USD in 2025 and is projected to reach roughly 53 billion USD by 2034, growing at around 4–5% per year as fertilizer, metals, and chemical demand rises.

The sulfur market itself – the feedstock for that acid – is smaller in value but just as strategic. Estimates put the global sulfur market at roughly 9–11 billion USD in 2025, with slow but steady growth of about 3–4% annually through the 2030s. Almost all of that sulfur ends up in sulfuric acid: on the order of 90% of global sulfur production is ultimately transformed into H₂SO₄.

Sulfur as a nutrient

About 60–70% of sulfuric acid demand still comes from agriculture, primarily phosphate fertilizers. But that headline hides something deeper than process chemistry. When sulfuric acid digests phosphate rock, it doesn’t just make phosphorus bio‑available; it also leaves sulfur behind in the final fertilizer product.

Sulfur is an essential element for life. It is part of amino acids like cysteine and methionine, meaning it is literally part of the machinery that builds proteins in both plants and animals. Modern high‑yield crops are effectively “sulfur‑hungry” because they remove more sulfur from soils with every harvest, ironically the older atmospheric pollution that used to supply sulfur via acid rain has been sharply reduced by environmental regulations.

So sulfuric acid ties into food security in two ways at once:

· It is the reagent that unlocks phosphate rock.

· It is itself a nutrient source embedded in fertilizers alongside nitrogen, phosphorus, and potassium (N, P, K).

When sulfuric acid supply tightens, fertilizer prices rise, and that quickly bleeds into food prices and political stability.

How sulfur moves: two byproduct pillars

To understand why the system is fragile, you have to start at the beginning of the chain. Sulfur today moves along two main byproduct pillars, not as a primary commodity.

Recovered sulfur from sour crude and natural gas.

Refineries and gas plants use hydrodesulfurisation to strip sulfur as hydrogen sulfide, then use the Claus process to convert H₂S into molten elemental sulfur. That sulfur is solidified, stockpiled, and loaded onto ships or trains.

Smelter‑acid from metal mines.

Sulfide ores – copper, zinc, nickel, lead – are roasted or smelted, producing sulfur dioxide (SO₂) in the off‑gas. Modern smelters must capture that SO₂ to avoid air‑pollution breaches, routing the cleaned gas into a sulfuric acid plant. In the contact process, SO₂ is oxidised to SO₃ over a vanadium catalyst, then absorbed into existing acid to form oleum, and finally diluted to make more H₂SO₄.

In both cases, sulfur is a byproduct of decisions made for other reasons – to produce fuels and metals, or to meet environmental regulations. There is very little “primary sulfur mining” left in the world. That means sulfur supply is constrained by hydrocarbon and metals production and policy, not by straightforward sulfur geology.

A chokepoint called Hormuz

This is where geography intrudes. The Middle East, and especially the Gulf, has become the world’s key exporter of recovered sulfur.

Gulf and wider Middle Eastern producers supply roughly 24% of global sulfur output, but account for around 45% of sulfur exports and close to half of seaborne sulfur trade. Much of that export volume moves through one narrow strait: Hormuz.

This matters because many of the most sulfur‑intensive parts of the green transition do not sit in the Gulf at all – they sit thousands of kilometres away but rely on Gulf sulfur as feedstock. Indonesian high‑pressure acid leach (HPAL) plants for laterite nickel battery materials are the clearest example.

Recent reporting suggests Indonesia imports on the order of three‑quarters of its sulfur from the Middle East, overwhelmingly via seaborne cargoes that must transit Hormuz. When conflict in West Asia disrupts those flows, Indonesian HPAL operators scramble for alternative sources, and sulfuric acid prices spike.

The same chokepoint also touches phosphate fertilizer complexes in Asia and North Africa and acid‑dependent metals operations from Chile to the Congo.

China steps back just as the Gulf stumbles

Into this already tight system comes another shock: China, which is both a huge consumer and the single largest exporter of sulfuric acid by volume, is now restricting exports.

In 2024 China exported roughly 300–350 million USD of sulfuric acid, more than any other country. Much of this acid is a byproduct of copper and zinc smelting rather than sulfur burning, which made it a critical swing supply for Latin American miners and regional fertilizer plants.

With Hormuz disruptions cutting off about a third of global sulfur flows and pushing prices higher, Beijing has moved to conserve acid for domestic fertilizer and industrial use, halting or sharply curbing exports from May 2026 through at least year‑end.

That combination – Gulf sulfur under pressure, Chinese acid stepping back – removes two of the system’s main safety valves at once. Some copper producers are reportedly down to 30–60 days of sulfur or acid inventory, and warnings of production cuts are already surfacing.

The irony is that China itself produces roughly a fifth of global sulfuric acid output, anchored by its fertilizer and metals industries. When there is a crunch, Beijing is signalling that its own food and industrial security takes priority, even if that means exporting the shock to others – much as it has done in past rare earth or phosphate fertilizer squeezes.

Net‑zero’s sulfur paradox

All of this sets up the sulfuric‑acid version of a resource trap that researchers have started to call the “sulfur cliff”. A 2022 analysis from UCL and collaborators argues that global demand for sulfuric acid could exceed 400 million tonnes per year by 2040, driven by fertilizer, green metals, and industrial growth, while supply from conventional sources struggles to keep up.

The paradox is stark: To decarbonise, we want to burn less oil and gas and clean up remaining fossil fuels more aggressively. But that same decarbonisation shrinks the pool of recovered sulfur that now feeds almost all sulfuric acid production essential for green metals.

Under some scenarios UCL’s work suggests that, without intervention, sulfuric acid supply could face a shortfall on the order of hundreds of millions of tonnes by mid‑century – a triple‑digit‑percent gap relative to current output.

One theoretical solution is to revive “primary sulfur mining”: deliberately extracting sulfur from subsurface deposits (for example via Frasch‑type methods) or from high‑sulfur minerals like pyrite, purely to make sulfuric acid. That would make sulfur more like a conventional mined commodity, but at significant capital cost and with new environmental burdens. Another is to expand smelter‑gas capture, tying sulfur supply even more tightly to copper and nickel mining.

Either way, sulfur stops being a free byproduct of fossil‑fuel refining and becomes a mineral in its own right – with all the politics and permitting headaches that implies.

Food, metals, grids, and data centres

It is easy to see the agricultural risk in a sulfur crunch, but the metals and technology side is just as serious. Sulfuric acid is central to:

Copper and cobalt: heap leaching of low‑grade copper ores, pressure leaching of cobalt‑bearing concentrates, and impurity control in refineries all rely on large volumes of acid.

Nickel and laterites: Indonesian HPAL plants converting nickel laterites into battery‑grade intermediates consume huge quantities of sulfuric acid per tonne of nickel produced.

Lithium and other battery materials: acid leach steps and downstream chemical processing repeatedly use sulfuric acid.

Without sufficient sulfuric acid, you constrain copper and cobalt production, which in turn constrains power grids, transformers, electric vehicles, semiconductors, and defence systems. Recent strategic commentary has begun to highlight sulfur and sulfuric acid as overlooked enablers of military readiness and critical infrastructure expansion.

Data centres and digital infrastructure tie in more indirectly but no less importantly. The surge in AI and cloud capacity is driving demand for:

· More electricity and grid reinforcement (copper, aluminium, transformers).

· More semiconductors (copper, specialty metals, chemical etching).

· More back‑up power and thermal management systems.

Sulfuric acid is used in semiconductor fabrication (cleaning, etching, and surface preparation), in producing some high‑purity chemicals used in chipmaking, and in the metals supply chains that build server racks, cooling systems, and grid connections feeding data centres. As data‑centre build‑out accelerates, it quietly adds to the same pool of acid demand already strained by fertilizers and battery metals.

Can North America and others fill the gap?

One obvious question is whether other regions can step up if Gulf sulfur is disrupted and China hoards its acid. North America looks, on paper, like a plausible backstop: it has significant sour oil and gas, large refining and gas‑processing capacity, and a mature sulfur recovery and acid industry.

In practice, the picture is mixed. North American sulfur production and sulfuric acid capacity are already heavily committed to domestic fertilizer, metals, and chemical demand. Building new sulfuric acid plants or debottlenecking existing ones is not instantaneous; typical timelines are 2–3 years for permitting and construction. Shipping acid over long distances is more complex and costly than shipping solid sulfur. It requires specialised tankers, terminals, and storage, all of which are currently sized for “normal” trade flows.

So while North America and other sulfur‑rich regions can increase exports at the margin, they are unlikely to fully replace a prolonged Gulf disruption and simultaneous Chinese export retreat. The world built its sulfur balance sheet around the assumption that byproduct sulfur from fossil fuels and smelters would always be abundant and cheap. That assumption is now in question.

Markets, growth, and the sulfur squeeze

Market data give a sense of how tight things already are. Analysts estimate that:

The global sulfur market in value terms is growing in the low‑single‑digits, from roughly 6–11 billion USD in the mid‑2020s toward the mid‑teens by the early 2030s.

The sulfuric acid market is larger and more dynamic, estimated at 14–35 billion USD in 2025 depending on methodology and price assumptions, and projected to grow to somewhere between the low‑20s and low‑50s billion USD by the early 2030s.

Asia‑Pacific already accounts for roughly half of global sulfuric acid market revenue and production, thanks to China, India, and other industrialising economies.

Recent supply shocks and price spikes have pushed sulfuric acid market valuations temporarily higher than underlying consumption growth would suggest, underscoring how sensitive the system is to disruptions in just a few key regions.

The mineral imperative: boring bulks, critical foundations

Sulfur illustrates a broader mineral imperative that is easy to miss when the focus is on glamorous critical minerals like lithium or rare earths. Sulfur is not geologically rare. What is scarce is the combination of infrastructure, policy alignment, and trade routes that turns that elemental abundance into usable sulfuric acid.

The lesson from Hormuz – and from China’s new export restrictions – is that in a pinch, all minerals can become critical. The supposedly boring bulks like sulfur and hydrocarbons remain the foundations of food systems, metals production, and digital infrastructure, and those foundations are unusually vulnerable right now. Demand for energy and raw materials is growing faster than the world’s ability to expand stable supply, and sulfur is one of the clearest warning lights on the dashboard.

Policy and investment: reading the rotten‑egg gauge

What does sulfur tell us about the global economy? Several things at once:

Interdependence: Food security, green‑tech metals, semiconductors, and data centres all draw on the same sulfuric acid pool. Stress in one segment quickly spills into others.

Byproduct risk: Building critical systems on top of byproduct supply exposes you to second‑order shocks – changes in oil output, smelter economics, or environmental rules can hit sulfuric acid harder than they hit the primary products.

Chokepoint exposure: A handful of maritime passages and policy decisions – Hormuz, Chinese export controls, Gulf refinery investment – can swing global sulfur and acid balances.

Transition tension: Net‑zero pathways that ignore sulfur risk generating green bottlenecks: more pressure on copper, nickel, and fertilizer, but less recovered sulfur to sustain them.

For policymakers, sulfur and sulfuric acid should be treated as early‑warning gauges. Tracking sulfur balances, diversifying sources, investing in smelter‑gas capture and (where justified) primary sulfur projects, and protecting key chokepoints could all reduce systemic risk.

For investors, the lesson is more uncomfortable: the constraints on this transition may be set not by headline critical minerals but by the boring, corrosive liquids and bulk elements that make everything else possible. When you smell rotten eggs in the news – Hormuz, sulfur prices, Chinese acid bans – you are really smelling stress in the foundations of the global economy.