Hydrogen can be produced from coal through a process called coal gasification. This process involves reacting coal with oxygen and steam at high temperatures and pressures to produce a synthetic gas, or syngas, composed primarily of hydrogen and carbon monoxide. The syngas is then further processed to separate and purify the hydrogen.

While hydrogen produced from coal can be used as a clean-burning fuel, the coal gasification process itself is not considered a clean technology. Coal gasification plants emit greenhouse gases, including carbon dioxide and methane, as well as other pollutants such as sulfur dioxide and nitrogen oxides. Additionally, coal mining and transportation can also result in environmental impacts.

To mitigate the environmental impacts of coal gasification, carbon capture and storage (CCS) technologies can be employed to capture and store the carbon dioxide produced during the process. However, CCS technologies are still in development and are not yet widely implemented at commercial scale.

Overall, while hydrogen produced from coal can be a clean-burning fuel, the coal gasification process itself is not considered a clean technology. Further advancements in CCS technologies and alternative methods of hydrogen production are needed to make hydrogen from coal a truly clean fuel.