Chapter 7: Can Plants, Waste and Water Really Fuel Our Future?

The Big Idea

Plants capture the Sun’s energy as they grow. We can turn crops and waste into fuels like ethanol and biogas. We can also use clean electricity to split water into hydrogen and oxygen. Hydrogen made this way is called green hydrogen, and it can power vehicles and factories without releasing carbon dioxide.

Did You Know?

India reached its goal of mixing 20% ethanol into petrol (called E20) in 2025, five years earlier than first planned. The National Green Hydrogen Mission, launched in 2023, aims to make India a major producer of green hydrogen.

Story Time — Riya and the Sweet Fuel

Riya, age 12 · Kolhapur, Maharashtra

Every winter, lines of tractors piled high with sugarcane rumble past Riya’s house near Kolhapur, on their way to the cooperative sugar mill. This year, Riya’s class visited the mill.

The manager showed them how cane is crushed to get juice for sugar. “But sugar is not our only product,” he said. “From the thick, dark leftover called molasses, and sometimes from cane juice, we make ethanol. It goes to oil companies, who mix it into petrol.”

“Why mix it?” Riya asked. “India imports most of its crude oil,” the manager explained. “Every litre of ethanol from our farms means less oil to buy from abroad, and more income for farmers.”

Then he pointed to the tall chimney. “And the dry crushed stalks, called bagasse, are burned in our boiler. The steam runs the mill and makes extra electricity for the grid.”

Riya noticed the smoke and frowned. “But burning makes carbon dioxide.” The manager nodded. “Good point. The cane took that carbon from the air while it grew, so the cycle is much closer to balanced than burning coal. But sugarcane also needs a lot of water, so we must not grow too much of it just for fuel.” Riya wrote down both sides — she knew her teacher would ask.

Story Time — Irfan Rides the Hydrogen Bus

Irfan, age 13 · Leh, Ladakh

Irfan lives in Leh, more than 3,500 metres above sea level. In winter, temperatures fall far below zero. So when India’s first commercial hydrogen fuel-cell buses started running in Leh in 2025, many people wondered whether they would survive the cold.

Irfan rode one to school. It was quiet, and the only thing coming out of the exhaust pipe was a little water vapour. “How can a bus run on water?” his little sister asked.

Irfan had read about it. “It doesn’t run on water. At a special station in Leh, a solar plant makes electricity. That electricity splits water into hydrogen and oxygen — this is called electrolysis. The hydrogen is stored in strong tanks on the bus.”

“Then inside a fuel cell, hydrogen joins with oxygen from the air. That makes electricity for the motor, and water is the only waste.” His sister giggled. “So it makes water to make water to make power!”

Irfan’s father added a practical note. “Hydrogen is still expensive to make, and it must be handled carefully because it catches fire easily. That’s why engineers are testing it here first.” Irfan looked at the snowy peaks and the sunny sky. “If it works in Ladakh,” he said, “it can work anywhere.”

🔢 Numbers Corner

Electrolysis: 2H₂O → 2H₂ + O₂. Fuel cell: 2H₂ + O₂ → 2H₂O + electricity. Making 1 kg of hydrogen needs about 9 litres of pure water and roughly 50 kWh of electricity.

Myth or Fact?

Myth: Biofuels are always good for the planet.

Fact: Not always. If forests are cut or too much water and fertiliser are used to grow fuel crops, the benefits shrink. Biofuels from waste and residues are usually the best choice.

🔬 Try it in the Green Energy Lab

Experiment with these ideas in Lab 5: Carbon Counter.

Brain Buster

Ask an adult to help you test a 9-volt battery with two pencil leads in salty water. Watch for tiny bubbles — that is electrolysis! (Do not touch the leads together, and do it only with supervision.)