“Steel, cement, plastics, and ammonia - without these four materials, there is no modern civilization. And making all four of them still depends overwhelmingly on fossil fuels.” — Vaclav Smil
When people discuss the energy transition, the conversation inevitably focuses on electricity - on solar panels, wind turbines, and electric vehicles. But the deeper foundation of modern civilization is not electricity. It is four materials: steel, cement, plastics, and ammonia. These four substances are the true pillars of modernity, and their production remains overwhelmingly dependent on fossil fuels in ways that cannot be easily changed.
Smil examines each material with his characteristic combination of historical depth and quantitative precision, making visible something that most people have never thought about: that the clothes we wear, the buildings we live in, the food we eat, and the packages our goods arrive in are all products of a fossil-fuel-dependent materials economy.
Steel is arguably the single most important material in modern civilization. It is used in buildings, bridges, railways, ships, cars, appliances, machinery, and pipelines. Global production in 2020 was approximately 1.9 billion tonnes - about 250 kilograms for every person on Earth.
The carbon challenge of steel is fundamental: the dominant production method, blast furnace steelmaking, requires coke (derived from coal) not merely as a fuel but as a chemical reducing agent to strip oxygen from iron ore. You cannot simply electrify this process with renewable electricity - the chemistry itself requires carbon.
The common narrative: We can make green steel using hydrogen or electric arc furnaces powered by renewables.
The quantitative reality: “Green” hydrogen-based steel production exists at pilot scale and faces enormous cost and energy challenges. Electric arc furnaces (which recycle scrap steel) can use renewable electricity, but they cannot produce primary steel from iron ore. Global demand for primary steel from ore remains enormous. Green steel at scale is decades away and will require vast amounts of renewable electricity that does not yet exist.
Cement, combined with water and aggregate, produces concrete - the most widely used construction material on Earth. More than 4 billion tonnes of cement are produced each year. The Great Wall of China, the Hoover Dam, the Chunnel, your nearest highway - all are products of cement and concrete.
The emissions problem of cement is even more fundamental than that of steel. Approximately 60% of cement’s CO₂ emissions come not from burning fuel but from the chemistry of production itself: heating limestone (calcium carbonate) releases CO₂ as calcium oxide (lime) is formed. This process emission cannot be eliminated simply by switching to a renewable fuel source.
Decarbonizing cement requires either:
Plastics are derived from petroleum and natural gas feedstocks. Global production has grown from virtually nothing in 1950 to approximately 370 million tonnes per year today. They are ubiquitous: in packaging, medical devices, electronics, textiles (polyester), building insulation, and thousands of other applications.
The decarbonization challenge of plastics is twofold:
Bioplastics - made from plant materials rather than petroleum - exist but currently represent a tiny fraction of total production and face challenges of cost, performance, and land use competition with food production.
As discussed in Chapter 2, the Haber-Bosch synthesis of ammonia is one of the most consequential inventions in human history. Ammonia is the foundation of synthetic nitrogen fertilizers that feed approximately half of humanity.
But ammonia’s dependence on fossil fuels is deep: the hydrogen used in Haber-Bosch synthesis is currently derived almost entirely from natural gas through steam methane reforming. Producing “green ammonia” using hydrogen made from electrolysis powered by renewable electricity is theoretically possible but currently 3-4 times more expensive than conventional ammonia.
The stakes of this challenge are not abstract: if ammonia production were disrupted, crop yields would collapse and billions of people would face food insecurity.
| Material | Global Production (2020) | Primary Fossil Dependency |
|---|---|---|
| Steel | ~1.9 billion tonnes | Coal (coking) |
| Cement | ~4.2 billion tonnes | Coal + process emissions |
| Plastics | ~370 million tonnes | Petroleum/gas feedstock |
| Ammonia | ~180 million tonnes | Natural gas (hydrogen) |
The combined material flow is staggering. And virtually none of it can be produced without fossil fuels using currently deployed technology.
Discussions of decarbonization that focus exclusively on electricity and transportation systematically ignore these four materials. Yet they are indispensable to modern civilization. There is no plausible path to net-zero emissions that does not address how they are produced.
This is not a counsel of despair. It is a call for honest accounting of what the energy and materials transition actually involves - so that solutions can be designed and funded at the appropriate scale.
Look around wherever you are right now. How many objects or structures can you see that contain steel, cement, plastic, or are products of synthetic nitrogen fertilizer? What would your environment look like if these four materials suddenly became unavailable?