📖 Chapter 6 of 12 · Green Energy - Advance 2 · Class 9–10
Chapter 6: Can We Make Steel, Cement and Fertiliser Without Coal?
In this chapter
- Why heavy industry is called “hard to abate”.
- Green hydrogen and direct reduced iron.
- Cement’s chemistry problem, and carbon capture.
- Meet Ipsita from Odisha and Vikram from Rajasthan.
The Big Idea
Some industries do not merely burn fossil fuels — they need them chemically. Steel-making uses carbon to strip oxygen from iron ore. Cement releases CO₂ from limestone itself. Fertiliser needs hydrogen, today made from natural gas. To clean these industries we must change the chemistry: green hydrogen instead of carbon, electric heat instead of flames, new cement recipes, and capturing the CO₂ that remains.
Did You Know?
India’s National Green Hydrogen Mission, launched in 2023, targets about 5 million tonnes of green hydrogen production a year by 2030. The first users are expected to be refineries and fertiliser plants, which already use large amounts of hydrogen made from fossil fuels.
Story Time — Ipsita and the Iron Without Fire
Ipsita, age 16 · Angul, Odisha
Ipsita lives in Angul, a steel town in Odisha where the skyline is chimneys. In chemistry class she learned the reaction that built her town: iron oxide plus carbon gives iron plus carbon dioxide.
“So the CO₂ is not an accident,” she said slowly. “It is the product of the reaction.” Her teacher agreed. “That is exactly why steel is hard to clean. The carbon is doing a job.”
On a plant visit, an engineer showed her the alternative: direct reduced iron. “We can use hydrogen instead of carbon. Then iron oxide plus hydrogen gives iron plus water. If that hydrogen is made by electrolysis with clean electricity, the steel is nearly carbon-free.”
Ipsita asked why the whole plant had not switched. The engineer was frank. “Green hydrogen still costs much more than coal here. We would need cheap renewable power all day, a huge electrolyser, and furnaces rebuilt for hydrogen. Pilot plants are running in India and abroad, but this is a decade-long change, not a switch on a wall.”
Ipsita chose her project title that evening: “The steel in a wind turbine should one day be made by wind.”
Story Time — Vikram and the Limestone Problem
Vikram, age 15 · Chittorgarh, Rajasthan
Vikram’s father is a foreman at a cement plant near Chittorgarh. Vikram assumed the plant’s emissions came from the fuel burnt in the kiln. His father corrected him with a piece of chalk.
“Limestone is calcium carbonate. Heat it and you get calcium oxide — the clinker we need — plus carbon dioxide. That gas comes out of the rock, not the flame. Even a kiln fired entirely by solar heat would still release it.”
Vikram was startled: roughly 60% of a cement plant’s CO₂ comes from this chemical reaction, and the rest from the fuel needed to reach about 1,450°C.
So what can be done? His father listed the plant’s efforts: replacing some coal with biomass and waste-derived fuel; grinding in fly ash and slag to make blended cements that need less clinker; and studying carbon capture, where CO₂ is separated from the exhaust and stored or used.
“And the cheapest step of all,” he added, tapping a pillar, “is using less cement. Better design, less waste, longer-lasting buildings.” Vikram wrote it down as his first rule of engineering: “The greenest tonne is the one you never had to make.”
Green Steel: Swapping Carbon for Hydrogen
A blast furnace uses coke (carbon) as both fuel and reducing agent, so CO₂ is unavoidable. In hydrogen-based direct reduction, hydrogen strips the oxygen from iron ore in the solid state, producing sponge iron and water vapour. The sponge iron is then melted in an electric arc furnace, which can run on clean electricity.
- Blast furnace: Fe₂O₃ + 3CO → 2Fe + 3CO₂.
- Hydrogen DRI: Fe₂O₃ + 3H₂ → 2Fe + 3H₂O.
- Steel accounts for a large share of global industrial emissions, and India is the world’s second-largest steel producer.
- Recycled steel melted in an electric arc furnace uses far less energy than making iron from ore.
Cement, Heat and Carbon Capture
CaCO₃ → CaO + CO₂ is the reaction at the heart of cement. Because the gas comes from the rock, cleaner fuel alone cannot solve it. The options are to need less clinker, to capture the CO₂, or to invent different binders.
- Blended cements: fly ash, slag and calcined clay replace part of the clinker.
- Efficiency and design: using less concrete for the same strength cuts emissions directly.
- Carbon capture (CCUS): separate CO₂ from the exhaust, then store it underground or use it to make materials — promising but expensive and still small-scale.
- Electrification of heat: electric kilns and furnaces, plus hydrogen or biomass for very high temperatures.
- Fertiliser: ammonia needs hydrogen; green hydrogen can replace the natural gas used today.
🔢 Numbers Corner
Hydrogen for steel: roughly 50–60 kg of hydrogen is needed per tonne of iron by the direct-reduction route. At about 50 kWh of electricity per kg of hydrogen, one tonne of green iron needs on the order of 2,500–3,000 kWh of clean electricity.
Myth or Fact?
Myth: Industry can be cleaned up simply by connecting factories to solar power.
Fact: Clean electricity helps, but steel, cement and fertiliser also need chemical changes — hydrogen instead of carbon, new cement recipes, and capture of the CO₂ that chemistry itself releases.
🔬 Try it in the Green Energy Lab
Experiment with these ideas in Lab 4: Green Hydrogen Cost.
Solved Examples
Work it out first, then check the answer.
1. Why is cement described as “hard to abate”?
Show answer
Answer: Because about 60% of its CO₂ comes from decomposing limestone, a chemical reaction that happens whatever fuel heats the kiln.
2. Write the two reduction reactions for iron and state the difference.
Show answer
Answer: Blast furnace: Fe₂O₃ + 3CO → 2Fe + 3CO₂. Hydrogen DRI: Fe₂O₃ + 3H₂ → 2Fe + 3H₂O. The first releases carbon dioxide, the second releases water.
3. A plant makes 1,000 tonnes of green iron and uses 55 kg of hydrogen per tonne. How much hydrogen is needed?
Show answer
Answer: 1,000 × 55 = 55,000 kg = 55 tonnes of hydrogen.
4. At 50 kWh per kg of hydrogen, how much electricity does that need?
Show answer
Answer: 55,000 × 50 = 27,50,000 kWh = 2.75 GWh.
5. Why is recycled steel less energy-intensive than steel from ore?
Show answer
Answer: The iron has already been reduced, so no reduction reaction is needed; the scrap is simply melted, usually in an electric arc furnace.
Check Your Understanding
A. Fill in the blanks
- In a blast furnace, carbon removes from iron ore.
- In hydrogen direct reduction, the by-product is .
- About % of cement’s CO₂ comes from limestone itself.
- Capturing and storing CO₂ from exhaust gases is abbreviated .
- India’s National Green Hydrogen Mission targets about million tonnes a year by 2030.
B. True or False
- Cement emissions come only from burning fuel. ( ___ )
- Green hydrogen can replace coke as a reducing agent. ( ___ )
- Electric arc furnaces can run on renewable electricity. ( ___ )
- Using less cement is a legitimate emissions strategy. ( ___ )
C. Choose the correct option
- Calcium carbonate decomposes into calcium oxide and (a) oxygen (b) carbon dioxide (c) hydrogen
- Green hydrogen for industry is made by (a) electrolysis (b) burning coal (c) distilling oil
- India is the world’s (a) second (b) fifth (c) tenth largest steel producer
D. Answer in detail
- Explain why clean electricity alone cannot decarbonise cement.
- Describe the full route from a wind farm to a tonne of green steel.
- Argue whether India should prioritise green hydrogen for steel, fertiliser or transport first.
Brain Buster
Look at a cement bag: many are labelled PPC or PSC, meaning fly ash or slag has replaced some clinker. Why does that lower emissions?
Check your understanding
Tap an answer to see if it is correct. This is just for practice — nothing is saved.
1. Most of cement’s CO₂ comes from…
- The fuel
- The limestone decomposing
- The water
Show answer
B. The limestone decomposing
2. In hydrogen DRI, the by-product is…
- Carbon dioxide
- Water
- Methane
Show answer
B. Water
3. Green hydrogen is made by…
- Electrolysis with clean power
- Steam reforming of gas
- Burning biomass
Show answer
A. Electrolysis with clean power
4. Roughly how much electricity per kg of green hydrogen?
- 5 kWh
- 50 kWh
- 500 kWh
Show answer
B. 50 kWh
5. Which cuts emissions with no new technology at all?
- Using less cement through better design
- Bigger kilns
- More coke
Show answer
A. Using less cement through better design