Metallurgy, such as steel-making processes, require reducing agents to get rid of the oxygen in metal ores. Using fossil coal for this is a large source of $\ce{CO2}$ globally. Recently, I have read a lot how green hydrogen is proposed as a replacement for the fossil coal as a reducing agent. I also believe that hydrogen has a few issues such as its adverse effect on some metals (embrittlement) and its difficult storage and transport.

Wouldn't other reducing agents that can be easily produced from renewable energies, such as $\ce{CH4}$ or $\ce{NH3}$, be much more useful replacements for coal in metallurgy? Or do these have some chemical disadvantages that make hydrogen a much better contender?

Metallurgy, such as steel-making processes, require reducing agents to get rid of the oxygen in metal ores. Using fossil coal for this is a large source of $\ce{CO2}$ globally. Recently, I have read a lot how green hydrogen is proposed as a replacement for the fossil coal as a reducing agent. I also believe that hydrogen has a few issues such as its adverse effect on some metals (embrittlement) and its difficult storage and transport.

Wouldn't other reducing agents that can be easily produced from renewable energies, such as $\ce{CH4}$ or $\ce{NH3}$, be much more useful replacements for coal in metallurgy? Or do these have some chemical disadvantages that make hydrogen a much better contender?

Exemplary references about direct iron ore reduction using methane:

• Clean iron production through direct reduction of mineral iron carbonate with low-grade hydrogen sources; the effect of reduction feed gas composition on product and exit gas composition
• Kinetics of Iron Ore Reduction by Methane for Chemical Looping Combustion

Metallurgy such as steel making processes require reducing agents to get rid of the oxygen in ores. Using fossil coal for this is a large CO2 source globally. Recently, I have read a lot how green hydrogen is proposed as a replacement for the fossil coal as reducing agent.

  I also believe that hydrogen has a few issues such as its adverse effect on some metals (embrittlement) and its difficult storage and transport.

Wouldn't other reducing agents that can be easily produced from renewable energies, such as CH4 or NH3, be much more useful replacements for coal in metallurgy or do these have some chemical disadvantages that make hydrogen a much better contender?

Metallurgy, such as steel-making processes, require reducing agents to get rid of the oxygen in metal ores. Using fossil coal for this is a large source of $\ce{CO2}$ globally. Recently, I have read a lot how green hydrogen is proposed as a replacement for the fossil coal as a reducing agent. I also believe that hydrogen has a few issues such as its adverse effect on some metals (embrittlement) and its difficult storage and transport.

Wouldn't other reducing agents that can be easily produced from renewable energies, such as $\ce{CH4}$ or $\ce{NH3}$, be much more useful replacements for coal in metallurgy? Or do these have some chemical disadvantages that make hydrogen a much better contender?