**Correct Option: B. Haber-Bosch process for ammonia synthesis** ### Detailed Explanation: The Haber-Bosch process is a method used to synthesize ammonia (NH₃) from nitrogen (N₂) and hydrogen (H₂) gases. This process is crucial for producing fertilizers, which are essential for modern agriculture. However, it is also associated with significant greenhouse gas emissions, primarily due to the hydrogen production method. 1. **Hydrogen Production**: The most common method for producing hydrogen for the Haber-Bosch process is through steam methane reforming (SMR). In this process, natural gas (primarily methane, CH₄) reacts with steam (H₂O) at high temperatures in the presence of a catalyst to produce hydrogen and carbon dioxide (CO₂): \[ CH₄ + H₂O \rightarrow CO + 3H₂ \] \[ CO + H₂O \rightarrow CO₂ + H₂ \] The overall reaction results in the release of CO₂, a significant greenhouse gas. 2. **Ammonia Production**: Once hydrogen is produced, it is combined with nitrogen from the air under high pressure and temperature to form ammonia: \[ N₂ + 3H₂ \rightarrow 2NH₃ \] While this step does not produce greenhouse gases, the initial hydrogen production is the main contributor to emissions. 3. **Scale of Emissions**: The Haber-Bosch process is responsible for a substantial portion of global CO₂ emissions due to the large-scale production of ammonia needed for fertilizers. It is estimated that the process contributes about 1-2% of global CO₂ emissions. ### Why Other Options Are Weaker: **A. Electrolysis of water**: - This process involves splitting water (H₂O) into hydrogen (H₂) and oxygen (O₂) using electricity. If the electricity comes from renewable sources (like wind or solar), this process can be nearly carbon-neutral. Even if fossil fuels are used to generate the electricity, the direct emissions from the electrolysis itself are minimal compared to the Haber-Bosch process. **C. Fractional distillation of crude oil**: - While this process does involve the separation of crude oil into various components (like gasoline, diesel, etc.), it does not directly produce greenhouse gases. The emissions occur when the refined products are burned as fuels, but the distillation process itself is not a significant source of greenhouse gases. **D. Solvay process for sodium carbonate production**: - The Solvay process primarily produces sodium carbonate (soda ash) from sodium chloride (table salt) and limestone (calcium carbonate). While it does release some CO₂ during the reaction, the overall greenhouse gas emissions are lower compared to the Haber-Bosch process, which is heavily reliant on fossil fuels for hydrogen production. ### Summary of Key Points: - The Haber-Bosch process is the primary industrial method for ammonia synthesis, heavily linked to greenhouse gas emissions due to hydrogen production from natural gas. - Other processes like electrolysis, fractional distillation, and the Solvay process either have minimal direct emissions or are less significant in terms of overall greenhouse gas contributions. - Understanding the sources of greenhouse gas emissions in industrial processes is crucial for addressing climate change and developing sustainable practices.