Natural gas
Explanation
The production of nitrogenous fertilisers, particularly urea, relies on ammonia ($NH_3$) as a key intermediate. The synthesis of ammonia via the Haber-Bosch process requires two primary raw materials: Nitrogen ($N_2$) and Hydrogen ($H_2$).Source of Hydrogen:
- Natural Gas: This is the most widely used feedstock for obtaining hydrogen in the fertiliser industry. Natural gas is primarily composed of methane ($CH_4$).
- Steam Reforming Process: Hydrogen is produced by reacting methane with steam at high temperatures and pressures in the presence of a catalyst (typically nickel).
The general reaction is: $CH_4 + H_2O \rightarrow CO + 3H_2$. - The hydrogen generated is then combined with nitrogen (extracted from the air) to synthesize ammonia, which is further processed with carbon dioxide to produce urea.
While hydrogen can also be produced from coal (via coal gasification) or naphtha, natural gas is the preferred source globally and in India due to its economic efficiency and ease of processing.
Key Takeaway: The primary natural resource used to obtain hydrogen for the production of urea fertilisers is Natural gas, utilized through the process of steam methane reforming.