Haber-Bosch Process

The Haber process enabled the production of synthetic nitrogen fertilisers, leading to a sevenfold rise in global food production during the 20th century. It is estimated that, without this process, one-third of the world's population would not have enough food.

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The Haber-Bosch Process

The Haber-Bosch process was developed by chemist Fritz Haber and engineers Robert Le Rossignol and Friedrich Kirchenbauer.
It is a method used to make ammonia (NH₃), which is the main ingredient in many fertilisers.
The process is essential because plants need nitrogen to grow, but they can’t use the nitrogen in the air directly. The Haber-Bosch process converts that nitrogen into a form plants can use.
How it works:
- Nitrogen (N₂) from the air is combined with hydrogen (H₂) under very high pressure and moderate heat.
- A special substance called a catalyst (usually iron) helps speed up the reaction.
- This creates ammonia, which can be used to fertilize crops and boost food production.

Nitrogen Molecule

Nitrogen (N₂) is abundant in the Earth’s atmosphere, with eight metric tonnes of nitrogen per square meter on Earth’s surface.
In its molecular form, nitrogen atoms are bonded by a triple bond (N≡N), which makes nitrogen inert and almost unusable directly by living organisms.
The triple bond requires 946 kJ/mol of energy to break, making it extremely difficult to convert nitrogen into a reactive form.

Nitrogen’s Role in Biology

When the nitrogen bond is broken, it can form compounds like ammonia (NH₃), ammonium (NH₄⁺), or nitrates (NO₃⁻), which are collectively known as reactive nitrogen.
Plants require these forms of nitrogen for synthesising essential biomolecules such as enzymes, proteins, and amino acids. Healthy plants have around 3-4% nitrogen in their tissues.

Availability of Nitrogen in Nature

Lightning can generate enough energy to break nitrogen bonds, creating nitrogen oxides (NO, NO₂), which react with water to form nitric and nitrous acids that fertilise soil during rainfall.
Certain bacteria like Azotobacter and symbiotic microorganisms like Rhizobia in legumes naturally convert atmospheric nitrogen into reactive nitrogen.
Azolla, an aquatic fern with Anabaena azollae bacteria, is another natural nitrogen converter.

The Nitrogen Cycle

Environmental Concerns with Nitrogen Fertilisers

Excessive nitrogen leads to environmental issues like:
- Acid rain formation due to reactive nitrogen in the atmosphere.
- Soil corrosion and degradation of agricultural land.
- Fertilisation and deoxygenation of freshwater and coastal ecosystems, resulting in the uncontrolled growth of weeds.
While fertilisers are essential for high crop yields, they also accelerate environmental damage and are not a complete solution to world hunger or malnutrition.