Haber-Bosch Process and Production of Fertilizers | 17 Oct 2024

Source: TH

Why in News?

Through the Haber-Bosch process, a hundred million tonnes of nitrogen are extracted from the atmosphere and transformed into fertiliser, resulting in the addition of 165 million tonnes of reactive nitrogen to the soil. 

• In comparison, natural biological processes generate an estimated 100-140 million tonnes of reactive nitrogen annually.  

What is the Haber-Bosch Process? 

• About:  
  • The Haber-Bosch process is an industrial method for synthesizing ammonia by combining nitrogen from the air with hydrogen, significantly contributing to fertiliser production. 
• Process: 
  • Experimental Setup: 
    • The reaction occurs in a steel chamber at a pressure of 200 atm, allowing the nitrogen-hydrogen mixture to circulate effectively. 
    • A specially designed valve withstands high pressure while allowing the N₂-H₂ mixture to flow through. 
    • Haber implemented a system to transfer heat from the outgoing hot gases to the incoming cooler gases, optimizing energy efficiency. 
  • Catalyst Development: 
    • Haber initially experimented with various materials looking for suitable filament materials as Catalyst to speed up reaction. 
    • Among the tested materials was osmium, which, when placed in the pressure chamber with the N₂-H₂ mixture, successfully cracked the nitrogen triple bond, allowing for ammonia production. 
      • Uranium was another effective catalyst but both osmium and uranium were too expensive for large-scale applications. 
      • The search for a more cost-effective catalyst led to the identification of specific iron oxides as viable options. 
• Applications:  
  • Manufacturing: As a refrigerant in industrial refrigeration systems and air conditioning.  
  • Household: An ingredient in household cleaning products, including glass and surface cleaners.  
  • Automotive fuel: An internal combustion engine powered by ammonia is being explored as an alternative propulsion technology. 
  • Chemicals: A precursor for various chemicals, including nitric acid and explosives. 
• Key Milestones: 
  • In 1913, the German chemical company opened its first ammonia factory, marking a significant milestone in the production of fertilizers. 
  • Fritz Haber, a German chemist, won the Nobel Prize in Chemistry in 1919 for his work on ammonia synthesis. 

What is the Nitrogen Cycle? 

• About: 
  • Plants obtain reactive nitrogen from the soil by absorbing nitrogen-based minerals like ammonium (NH4+) and nitrate (NO3–), dissolved in water. 
  • Humans and animals rely on plants for nine essential nitrogen-rich amino acids, as nitrogen makes up about 2.6% of the human body. 
  • After being ingested, nitrogen returns to the soil through excreta and decomposition of dead organisms, but some nitrogen escapes back into the atmosphere as molecular nitrogen, leaving the cycle incomplete. 
• Natural Availability of Nitrogen: 
  • Lightning: Lightning bolts possess enough energy to break the N2 bond, combining nitrogen with oxygen to form nitrogen oxides (NO and NO2).  
    • These oxides mix with water vapour, forming nitric and nitrous acids, which fall as acid rain, providing reactive nitrogen to the soil. 
  • Biological Fixation: Some bacteria, like Azotobacter and Rhizobia, can convert atmospheric nitrogen into reactive nitrogen.  
    • These bacteria often have symbiotic relationships with plants such as legumes or aquatic ferns like Azolla, which enhance nitrogen availability in the soil, making them valuable for agriculture. 
  • Process of Nitrogen Replenishment: 
    • While legumes can fix nitrogen naturally, most staple crops like rice, wheat, corn, potatoes, cassava, bananas, and other fruits and vegetables depend on soil nitrogen for growth. 
    • As human populations grow, the depletion of nitrogen in agricultural soils accelerates, requiring the use of fertilizers to restore soil fertility. 
  • Historical Fertilization Methods: 
    • Farmers historically cultivated legumes to naturally replenish nitrogen in the soil or applied ammonia-based fertilizers to increase crop yields. 
    • They also utilized ammonium-rich minerals from volcanic eruptions and naturally occurring nitrates found in caves and rocks to enhance soil fertility.

What is the Impact of Industrial Production of Fertilizers? 

• Pros: 
  • The Haber-Bosch process enabled the mass production of synthetic fertilizers, significantly boosting global food supply during the 20th century, contributing to increased life expectancy. 
  • An estimated one-third of the world's population relies on food produced using nitrogen fertilizers.  
    • Without the industrial production of ammonia from nitrogen and hydrogen, it would have been impossible to meet the growing global demand for food. 
• Cons: 
  • Synthetic nitrogen fertilizers, although critical for food production, have adverse environmental impacts. 
  • Excess nitrogen application leads to plant over-nourishment, boosting bacterial activity and accelerating nitrogen release into the atmosphere. 
  • This contributes to environmental degradation, including acid rain, land corrosion, and surface water deoxygenation through runoff, causing excessive weed growth in water bodies. 

Way Forward

• Promote Sustainable Fertilizer Use: Encourage the adoption of precision agriculture and controlled-release fertilizers to reduce nitrogen waste, minimize environmental damage, and enhance the efficiency of fertilizer usage in farming. 
• Invest in Alternative Technologies: Develop and promote eco-friendly alternatives to synthetic fertilizers, such as organic farming practices, nitrogen-fixing crops, and biofertilizers, to mitigate the environmental impacts of chemical fertilizers. 
• Strengthen Policy Frameworks: Governments should implement regulations to control fertilizer overuse and incentivize sustainable farming practices, ensuring food security while protecting ecosystems and public health. 
• Enhance Global Cooperation: Foster international collaboration to address food distribution disparities, improve access to agricultural innovations, and support capacity-building initiatives for regions facing food insecurity, ensuring equitable solutions to global food challenges.